feat(rust): port legacy v0.1 decoder

Port lib/legacy/zstd_v01.c (the frozen zstd v0.1 decoder) to
rust/src/legacy/zstd_v01.rs as the first legacy-format port on the new
scaffolding, and reduce the C file to a declaration-only shim that
keeps its header includes for configuration and platform preprocessor
behavior.

Frozen-decoder policy: zstd_v01.c embeds its own v0.1-era FSE and
Huff0 snapshot, distinct from every other release. The Rust port is a
line-by-line translation with the same table layouts (FSE_DTable as a
u32 header word plus packed newState/symbol/nbBits entries, the Huff0
u16 DTable with byte/nbBits pairs), the same arithmetic including
wrap-around and pointer-comparison quirks (e.g. the offset-vs-base
address check in ZSTD_execSequence), the same internal FSE error space
(size_t)-1..-7, and the same public ZSTD error codes. It reuses no
modern Rust entropy module; its only crate dependency is `errors`,
matching the C file's error_private.h include. The 32-bit-only reload
points are kept as compile-time conditions on usize::BITS.

Symbol takeover boundary: all nine ZSTDv01_* entry points from
zstd_v01.h now come from Rust as context-free #[no_mangle] extern "C"
functions (isError, decompress, decompressDCtx,
findFrameSizeInfoLegacy, createDCtx, freeDCtx, resetDCtx,
nextSrcSizeToDecompress, decompressContinue). zstd_legacy.h only uses
the first four for v0.1; streaming for v0.1-v0.3 intentionally returns
version_unsupported there, unchanged. The ZSTDv01_Dctx struct
definition moves entirely into Rust: C code only ever holds an opaque
pointer (zstd_v01.h forward-declares the type), and the context is
malloc/free-allocated exactly like the C version so create/free may
pair across the language boundary.

Byte-identity verification against the pristine pre-migration C build
(f8745da6, pure C, ZSTD_LEGACY_SUPPORT=1):

- Real v0.1 frames were generated by building the v0.1.0 git tag and
  compressing text, random, and 426 KB multi-block inputs. A one-shot
  ZSTD_decompress harness linked once against the pristine C libzstd.a
  and once against the Rust-backed libzstd.a produced bit-identical
  outputs for all frames.
- A direct ZSTDv01_* probe (one-shot decode, dst-too-small, truncated
  input, bad magic, findFrameSizeInfoLegacy, and the streaming
  continue loop) printed identical results, including exact error
  codes (-70 dstSize_tooSmall, -72 srcSize_wrong, -10 prefix_unknown)
  and identical dBound values.
- zstd -l -v on v0.1 files matches the pristine binary; CLI streaming
  decode of v0.1 fails with the same "Version not supported" in both,
  by design of zstd_legacy.h.

Unit tests embed three v0.1.0-generated fixtures (entropy-coded,
raw-block, and four-block frames) plus the truncation, bad-magic,
small-destination, and streaming-API cases, all asserting the exact C
error codes above. Note that `make -C tests test-legacy` only covers
v0.4+ frames, so the embedded fixtures and the harness comparison are
the actual v0.1 coverage.

Test plan:
- cd rust && cargo fmt --check && cargo clippy --all-targets
  --features legacy-v01 -- -D warnings && cargo test --all-targets
  --features legacy-v01 (127 tests, 9 for v0.1)
- cargo clippy/test --no-default-features --features
  decompression,legacy-v01 (module builds standalone)
- make -C tests fuzzer && ./tests/fuzzer -i1 --no-big-tests, also with
  ZSTD_LEGACY_SUPPORT=1 (mixed Rust v0.1 + C v0.2-0.7 link)
- make -C tests test-rust-lib-smoke && make -C tests test-legacy
- make -C programs zstd (default and ZSTD_LEGACY_SUPPORT=1); nm shows
  the nine ZSTDv01_* symbols provided by Rust at level 1
- make -C lib libzstd.a ZSTD_LEGACY_SUPPORT=0 (no legacy symbols) and
  meson -Dlegacy_level=1 shared library exporting all nine

.gitignore

@@ -34,6 +34,7 @@ install/
 
 # Build artefacts
 /rust/target/
+/rust/cli/target/
 contrib/linux-kernel/linux/
 projects/
 bin/

build/cmake/lib/CMakeLists.txt

@@ -169,6 +169,18 @@ elseif(_zstd_huf_force_x2)
     endif()
 endif()
 
+# This CMake build compiles every lib/legacy/zstd_v0N.c whenever legacy
+# support is enabled (ZSTD_LEGACY_LEVEL only selects the C dispatch), so the
+# Rust archive enables every per-version legacy feature to match.  The build
+# configuration encodes the switch so archives never mix.
+set(_zstd_rust_legacy 0)
+if(ZSTD_LEGACY_SUPPORT)
+    set(_zstd_rust_legacy 1)
+    list(APPEND _zstd_rust_features
+         legacy-v01 legacy-v02 legacy-v03 legacy-v04
+         legacy-v05 legacy-v06 legacy-v07)
+endif()
+
 set(_zstd_rust_target "${ZSTD_RUST_TARGET}")
 if(NOT _zstd_rust_target AND CMAKE_SYSTEM_NAME STREQUAL "Linux"
         AND CMAKE_SIZEOF_VOID_P EQUAL 4)
@@ -195,7 +207,7 @@ if(_zstd_rust_features)
 endif()
 
 set(_zstd_rust_build_config
-    "c${_zstd_rust_compression}-d${_zstd_rust_decompression}-b${_zstd_rust_dictbuilder}-${_zstd_rust_huf_mode}")
+    "c${_zstd_rust_compression}-d${_zstd_rust_decompression}-b${_zstd_rust_dictbuilder}-${_zstd_rust_huf_mode}-legacy${_zstd_rust_legacy}")
 set(ZSTD_RUST_MANIFEST "${ZSTD_SOURCE_DIR}/rust/Cargo.toml")
 set(ZSTD_RUST_TARGET_DIR
     "${CMAKE_CURRENT_BINARY_DIR}/rust-target/${_zstd_rust_build_config}")

build/meson/lib/meson.build

@@ -88,6 +88,16 @@ elif rust_huf_force_x2
   rust_huf_c_args += '-DHUF_FORCE_DECOMPRESS_X2'
 endif
 
+# Mirror the legacy source selection below: legacy_level N compiles
+# lib/legacy/zstd_v0N.c .. zstd_v07.c, so the Rust archive enables the
+# matching per-version features.  The build configuration encodes the level
+# so archives built for different legacy levels never mix.
+foreach i : [1, 2, 3, 4, 5, 6, 7]
+  if legacy_level != 0 and legacy_level <= i
+    rust_features += 'legacy-v0@0@'.format(i)
+  endif
+endforeach
+
 rust_target = get_option('zstd_rust_target')
 if rust_target == ''
   if host_machine_os == os_linux and \
@@ -98,7 +108,7 @@ if rust_target == ''
   endif
 endif
 
-rust_build_config = 'c1-d1-b1-' + rust_huf_mode
+rust_build_config = 'c1-d1-b1-' + rust_huf_mode + '-legacy@0@'.format(legacy_level)
 rust_target_dir = join_paths(meson.current_build_dir(), 'rust-target', rust_build_config)
 is_msvc = cc_id == compiler_msvc or cc_id == 'clang-cl'
 rust_staticlib_name = is_msvc ? 'zstd_rs.lib' : 'libzstd_rs.a'

lib/Makefile

@@ -104,6 +104,18 @@ ifneq ($(ZSTD_LIB_DECOMPRESSION),0)
 RUST_CARGO_FEATURES += $(RUST_HUF_FEATURE)
 endif
 endif
+
+# Legacy decoders follow the ZSTD_LEGACY_FILES selection exactly: level N
+# enables versions v0.N .. v0.7 (0 disables legacy).  The build directory
+# also encodes the level, so archives for different legacy levels never mix.
+RUST_LEGACY_FEATURES :=
+ifneq ($(ZSTD_LEGACY_SUPPORT), 0)
+ifeq ($(shell test $(ZSTD_LEGACY_SUPPORT) -lt 8; echo $$?), 0)
+RUST_LEGACY_FEATURES := $(addprefix legacy-v0,$(wordlist $(ZSTD_LEGACY_SUPPORT),7,1 2 3 4 5 6 7))
+endif
+endif
+RUST_CARGO_FEATURES += $(RUST_LEGACY_FEATURES)
+RUST_BUILD_CONFIG := $(RUST_BUILD_CONFIG)-legacy$(ZSTD_LEGACY_SUPPORT)
 RUST_CARGO_FEATURES := $(subst $(space),$(comma),$(strip $(RUST_CARGO_FEATURES)))
 
 RUST_TARGET ?=

lib/legacy/zstd_v01.c

@@ -17,2111 +17,7 @@
 #include "../common/compiler.h"
 #include "../common/error_private.h"
 
-
+/* Implementation moved to Rust (rust/src/legacy/zstd_v01.rs).
-/******************************************
+ * The frozen v0.1 decoder, including its embedded FSE/Huff0 snapshot and the
-*  Static allocation
+ * ZSTDv01_Dctx streaming state, now lives entirely in Rust; C code only ever
-******************************************/
+ * holds an opaque ZSTDv01_Dctx pointer. */
-/* You can statically allocate FSE CTable/DTable as a table of unsigned using below macro */
-#define FSE_DTABLE_SIZE_U32(maxTableLog)                   (1 + (1<<maxTableLog))
-
-/* You can statically allocate Huff0 DTable as a table of unsigned short using below macro */
-#define HUF_DTABLE_SIZE_U16(maxTableLog)   (1 + (1<<maxTableLog))
-#define HUF_CREATE_STATIC_DTABLE(DTable, maxTableLog) \
-        unsigned short DTable[HUF_DTABLE_SIZE_U16(maxTableLog)] = { maxTableLog }
-
-
-/******************************************
-*  Error Management
-******************************************/
-#define FSE_LIST_ERRORS(ITEM) \
-        ITEM(FSE_OK_NoError) ITEM(FSE_ERROR_GENERIC) \
-        ITEM(FSE_ERROR_tableLog_tooLarge) ITEM(FSE_ERROR_maxSymbolValue_tooLarge) ITEM(FSE_ERROR_maxSymbolValue_tooSmall) \
-        ITEM(FSE_ERROR_dstSize_tooSmall) ITEM(FSE_ERROR_srcSize_wrong)\
-        ITEM(FSE_ERROR_corruptionDetected) \
-        ITEM(FSE_ERROR_maxCode)
-
-#define FSE_GENERATE_ENUM(ENUM) ENUM,
-typedef enum { FSE_LIST_ERRORS(FSE_GENERATE_ENUM) } FSE_errorCodes;  /* enum is exposed, to detect & handle specific errors; compare function result to -enum value */
-
-
-/******************************************
-*  FSE symbol compression API
-******************************************/
-/*
-   This API consists of small unitary functions, which highly benefit from being inlined.
-   You will want to enable link-time-optimization to ensure these functions are properly inlined in your binary.
-   Visual seems to do it automatically.
-   For gcc or clang, you'll need to add -flto flag at compilation and linking stages.
-   If none of these solutions is applicable, include "fse.c" directly.
-*/
-
-typedef unsigned FSE_CTable;   /* don't allocate that. It's just a way to be more restrictive than void* */
-typedef unsigned FSE_DTable;   /* don't allocate that. It's just a way to be more restrictive than void* */
-
-typedef struct
-{
-    size_t bitContainer;
-    int    bitPos;
-    char*  startPtr;
-    char*  ptr;
-    char*  endPtr;
-} FSE_CStream_t;
-
-typedef struct
-{
-    ptrdiff_t   value;
-    const void* stateTable;
-    const void* symbolTT;
-    unsigned    stateLog;
-} FSE_CState_t;
-
-typedef struct
-{
-    size_t   bitContainer;
-    unsigned bitsConsumed;
-    const char* ptr;
-    const char* start;
-} FSE_DStream_t;
-
-typedef struct
-{
-    size_t      state;
-    const void* table;   /* precise table may vary, depending on U16 */
-} FSE_DState_t;
-
-typedef enum { FSE_DStream_unfinished = 0,
-               FSE_DStream_endOfBuffer = 1,
-               FSE_DStream_completed = 2,
-               FSE_DStream_tooFar = 3 } FSE_DStream_status;  /* result of FSE_reloadDStream() */
-               /* 1,2,4,8 would be better for bitmap combinations, but slows down performance a bit ... ?! */
-
-
-/****************************************************************
-*  Tuning parameters
-****************************************************************/
-/* MEMORY_USAGE :
-*  Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; etc.)
-*  Increasing memory usage improves compression ratio
-*  Reduced memory usage can improve speed, due to cache effect
-*  Recommended max value is 14, for 16KB, which nicely fits into Intel x86 L1 cache */
-#define FSE_MAX_MEMORY_USAGE 14
-#define FSE_DEFAULT_MEMORY_USAGE 13
-
-/* FSE_MAX_SYMBOL_VALUE :
-*  Maximum symbol value authorized.
-*  Required for proper stack allocation */
-#define FSE_MAX_SYMBOL_VALUE 255
-
-
-/****************************************************************
-*  template functions type & suffix
-****************************************************************/
-#define FSE_FUNCTION_TYPE BYTE
-#define FSE_FUNCTION_EXTENSION
-
-
-/****************************************************************
-*  Byte symbol type
-****************************************************************/
-typedef struct
-{
-    unsigned short newState;
-    unsigned char  symbol;
-    unsigned char  nbBits;
-} FSE_decode_t;   /* size == U32 */
-
-
-
-/****************************************************************
-*  Compiler specifics
-****************************************************************/
-#ifdef _MSC_VER    /* Visual Studio */
-#  define FORCE_INLINE static __forceinline
-#  include <intrin.h>                    /* For Visual 2005 */
-#  pragma warning(disable : 4127)        /* disable: C4127: conditional expression is constant */
-#  pragma warning(disable : 4214)        /* disable: C4214: non-int bitfields */
-#else
-#  define GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
-#  if defined (__cplusplus) || defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L   /* C99 */
-#    ifdef __GNUC__
-#      define FORCE_INLINE static inline __attribute__((always_inline))
-#    else
-#      define FORCE_INLINE static inline
-#    endif
-#  else
-#    define FORCE_INLINE static
-#  endif /* __STDC_VERSION__ */
-#endif
-
-
-/****************************************************************
-*  Includes
-****************************************************************/
-#include <stdlib.h>     /* malloc, free, qsort */
-#include <string.h>     /* memcpy, memset */
-#include <stdio.h>      /* printf (debug) */
-
-
-#ifndef MEM_ACCESS_MODULE
-#define MEM_ACCESS_MODULE
-/****************************************************************
-*  Basic Types
-*****************************************************************/
-#if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L   /* C99 */
-# include <stdint.h>
-typedef  uint8_t BYTE;
-typedef uint16_t U16;
-typedef  int16_t S16;
-typedef uint32_t U32;
-typedef  int32_t S32;
-typedef uint64_t U64;
-typedef  int64_t S64;
-#else
-typedef unsigned char       BYTE;
-typedef unsigned short      U16;
-typedef   signed short      S16;
-typedef unsigned int        U32;
-typedef   signed int        S32;
-typedef unsigned long long  U64;
-typedef   signed long long  S64;
-#endif
-
-#endif   /* MEM_ACCESS_MODULE */
-
-/****************************************************************
-*  Memory I/O
-*****************************************************************/
-
-static unsigned FSE_32bits(void)
-{
-    return sizeof(void*)==4;
-}
-
-static unsigned FSE_isLittleEndian(void)
-{
-    const union { U32 i; BYTE c[4]; } one = { 1 };   /* don't use static : performance detrimental  */
-    return one.c[0];
-}
-
-static U16 FSE_read16(const void* memPtr)
-{
-    U16 val; memcpy(&val, memPtr, sizeof(val)); return val;
-}
-
-static U32 FSE_read32(const void* memPtr)
-{
-    U32 val; memcpy(&val, memPtr, sizeof(val)); return val;
-}
-
-static U64 FSE_read64(const void* memPtr)
-{
-    U64 val; memcpy(&val, memPtr, sizeof(val)); return val;
-}
-
-static U16 FSE_readLE16(const void* memPtr)
-{
-    if (FSE_isLittleEndian())
-        return FSE_read16(memPtr);
-    else
-    {
-        const BYTE* p = (const BYTE*)memPtr;
-        return (U16)(p[0] + (p[1]<<8));
-    }
-}
-
-static U32 FSE_readLE32(const void* memPtr)
-{
-    if (FSE_isLittleEndian())
-        return FSE_read32(memPtr);
-    else
-    {
-        const BYTE* p = (const BYTE*)memPtr;
-        return (U32)((U32)p[0] + ((U32)p[1]<<8) + ((U32)p[2]<<16) + ((U32)p[3]<<24));
-    }
-}
-
-
-static U64 FSE_readLE64(const void* memPtr)
-{
-    if (FSE_isLittleEndian())
-        return FSE_read64(memPtr);
-    else
-    {
-        const BYTE* p = (const BYTE*)memPtr;
-        return (U64)((U64)p[0] + ((U64)p[1]<<8) + ((U64)p[2]<<16) + ((U64)p[3]<<24)
-                     + ((U64)p[4]<<32) + ((U64)p[5]<<40) + ((U64)p[6]<<48) + ((U64)p[7]<<56));
-    }
-}
-
-static size_t FSE_readLEST(const void* memPtr)
-{
-    if (FSE_32bits())
-        return (size_t)FSE_readLE32(memPtr);
-    else
-        return (size_t)FSE_readLE64(memPtr);
-}
-
-
-
-/****************************************************************
-*  Constants
-*****************************************************************/
-#define FSE_MAX_TABLELOG  (FSE_MAX_MEMORY_USAGE-2)
-#define FSE_MAX_TABLESIZE (1U<<FSE_MAX_TABLELOG)
-#define FSE_MAXTABLESIZE_MASK (FSE_MAX_TABLESIZE-1)
-#define FSE_DEFAULT_TABLELOG (FSE_DEFAULT_MEMORY_USAGE-2)
-#define FSE_MIN_TABLELOG 5
-
-#define FSE_TABLELOG_ABSOLUTE_MAX 15
-#if FSE_MAX_TABLELOG > FSE_TABLELOG_ABSOLUTE_MAX
-#error "FSE_MAX_TABLELOG > FSE_TABLELOG_ABSOLUTE_MAX is not supported"
-#endif
-
-
-/****************************************************************
-*  Error Management
-****************************************************************/
-#define FSE_STATIC_ASSERT(c) { enum { FSE_static_assert = 1/(int)(!!(c)) }; }   /* use only *after* variable declarations */
-
-
-/****************************************************************
-*  Complex types
-****************************************************************/
-typedef struct
-{
-    int deltaFindState;
-    U32 deltaNbBits;
-} FSE_symbolCompressionTransform; /* total 8 bytes */
-
-typedef U32 DTable_max_t[FSE_DTABLE_SIZE_U32(FSE_MAX_TABLELOG)];
-
-/****************************************************************
-*  Internal functions
-****************************************************************/
-FORCE_INLINE unsigned FSE_highbit32 (U32 val)
-{
-#   if defined(_MSC_VER)   /* Visual */
-    unsigned long r;
-    return _BitScanReverse(&r, val) ? (unsigned)r : 0;
-#   elif defined(__GNUC__) && (GCC_VERSION >= 304)   /* GCC Intrinsic */
-    return __builtin_clz (val) ^ 31;
-#   else   /* Software version */
-    static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 };
-    U32 v = val;
-    unsigned r;
-    v |= v >> 1;
-    v |= v >> 2;
-    v |= v >> 4;
-    v |= v >> 8;
-    v |= v >> 16;
-    r = DeBruijnClz[ (U32) (v * 0x07C4ACDDU) >> 27];
-    return r;
-#   endif
-}
-
-
-/****************************************************************
-*  Templates
-****************************************************************/
-/*
-  designed to be included
-  for type-specific functions (template emulation in C)
-  Objective is to write these functions only once, for improved maintenance
-*/
-
-/* safety checks */
-#ifndef FSE_FUNCTION_EXTENSION
-#  error "FSE_FUNCTION_EXTENSION must be defined"
-#endif
-#ifndef FSE_FUNCTION_TYPE
-#  error "FSE_FUNCTION_TYPE must be defined"
-#endif
-
-/* Function names */
-#define FSE_CAT(X,Y) X##Y
-#define FSE_FUNCTION_NAME(X,Y) FSE_CAT(X,Y)
-#define FSE_TYPE_NAME(X,Y) FSE_CAT(X,Y)
-
-
-
-static U32 FSE_tableStep(U32 tableSize) { return (tableSize>>1) + (tableSize>>3) + 3; }
-
-#define FSE_DECODE_TYPE FSE_decode_t
-
-
-typedef struct {
-    U16 tableLog;
-    U16 fastMode;
-} FSE_DTableHeader;   /* sizeof U32 */
-
-static size_t FSE_buildDTable
-(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog)
-{
-    void* ptr = dt;
-    FSE_DTableHeader* const DTableH = (FSE_DTableHeader*)ptr;
-    FSE_DECODE_TYPE* const tableDecode = (FSE_DECODE_TYPE*)(ptr) + 1;   /* because dt is unsigned, 32-bits aligned on 32-bits */
-    const U32 tableSize = 1 << tableLog;
-    const U32 tableMask = tableSize-1;
-    const U32 step = FSE_tableStep(tableSize);
-    U16 symbolNext[FSE_MAX_SYMBOL_VALUE+1];
-    U32 position = 0;
-    U32 highThreshold = tableSize-1;
-    const S16 largeLimit= (S16)(1 << (tableLog-1));
-    U32 noLarge = 1;
-    U32 s;
-
-    /* Sanity Checks */
-    if (maxSymbolValue > FSE_MAX_SYMBOL_VALUE) return (size_t)-FSE_ERROR_maxSymbolValue_tooLarge;
-    if (tableLog > FSE_MAX_TABLELOG) return (size_t)-FSE_ERROR_tableLog_tooLarge;
-
-    /* Init, lay down lowprob symbols */
-    DTableH[0].tableLog = (U16)tableLog;
-    for (s=0; s<=maxSymbolValue; s++)
-    {
-        if (normalizedCounter[s]==-1)
-        {
-            tableDecode[highThreshold--].symbol = (FSE_FUNCTION_TYPE)s;
-            symbolNext[s] = 1;
-        }
-        else
-        {
-            if (normalizedCounter[s] >= largeLimit) noLarge=0;
-            symbolNext[s] = normalizedCounter[s];
-        }
-    }
-
-    /* Spread symbols */
-    for (s=0; s<=maxSymbolValue; s++)
-    {
-        int i;
-        for (i=0; i<normalizedCounter[s]; i++)
-        {
-            tableDecode[position].symbol = (FSE_FUNCTION_TYPE)s;
-            position = (position + step) & tableMask;
-            while (position > highThreshold) position = (position + step) & tableMask;   /* lowprob area */
-        }
-    }
-
-    if (position!=0) return (size_t)-FSE_ERROR_GENERIC;   /* position must reach all cells once, otherwise normalizedCounter is incorrect */
-
-    /* Build Decoding table */
-    {
-        U32 i;
-        for (i=0; i<tableSize; i++)
-        {
-            FSE_FUNCTION_TYPE symbol = (FSE_FUNCTION_TYPE)(tableDecode[i].symbol);
-            U16 nextState = symbolNext[symbol]++;
-            tableDecode[i].nbBits = (BYTE) (tableLog - FSE_highbit32 ((U32)nextState) );
-            tableDecode[i].newState = (U16) ( (nextState << tableDecode[i].nbBits) - tableSize);
-        }
-    }
-
-    DTableH->fastMode = (U16)noLarge;
-    return 0;
-}
-
-
-/******************************************
-*  FSE byte symbol
-******************************************/
-#ifndef FSE_COMMONDEFS_ONLY
-
-static unsigned FSE_isError(size_t code) { return (code > (size_t)(-FSE_ERROR_maxCode)); }
-
-static short FSE_abs(short a)
-{
-    return a<0? -a : a;
-}
-
-
-/****************************************************************
-*  Header bitstream management
-****************************************************************/
-static size_t FSE_readNCount (short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
-                 const void* headerBuffer, size_t hbSize)
-{
-    const BYTE* const istart = (const BYTE*) headerBuffer;
-    const BYTE* const iend = istart + hbSize;
-    const BYTE* ip = istart;
-    int nbBits;
-    int remaining;
-    int threshold;
-    U32 bitStream;
-    int bitCount;
-    unsigned charnum = 0;
-    int previous0 = 0;
-
-    if (hbSize < 4) return (size_t)-FSE_ERROR_srcSize_wrong;
-    bitStream = FSE_readLE32(ip);
-    nbBits = (bitStream & 0xF) + FSE_MIN_TABLELOG;   /* extract tableLog */
-    if (nbBits > FSE_TABLELOG_ABSOLUTE_MAX) return (size_t)-FSE_ERROR_tableLog_tooLarge;
-    bitStream >>= 4;
-    bitCount = 4;
-    *tableLogPtr = nbBits;
-    remaining = (1<<nbBits)+1;
-    threshold = 1<<nbBits;
-    nbBits++;
-
-    while ((remaining>1) && (charnum<=*maxSVPtr))
-    {
-        if (previous0)
-        {
-            unsigned n0 = charnum;
-            while ((bitStream & 0xFFFF) == 0xFFFF)
-            {
-                n0+=24;
-                if (ip < iend-5)
-                {
-                    ip+=2;
-                    bitStream = FSE_readLE32(ip) >> bitCount;
-                }
-                else
-                {
-                    bitStream >>= 16;
-                    bitCount+=16;
-                }
-            }
-            while ((bitStream & 3) == 3)
-            {
-                n0+=3;
-                bitStream>>=2;
-                bitCount+=2;
-            }
-            n0 += bitStream & 3;
-            bitCount += 2;
-            if (n0 > *maxSVPtr) return (size_t)-FSE_ERROR_maxSymbolValue_tooSmall;
-            while (charnum < n0) normalizedCounter[charnum++] = 0;
-            if ((ip <= iend-7) || (ip + (bitCount>>3) <= iend-4))
-            {
-                ip += bitCount>>3;
-                bitCount &= 7;
-                bitStream = FSE_readLE32(ip) >> bitCount;
-            }
-            else
-                bitStream >>= 2;
-        }
-        {
-            const short max = (short)((2*threshold-1)-remaining);
-            short count;
-
-            if ((bitStream & (threshold-1)) < (U32)max)
-            {
-                count = (short)(bitStream & (threshold-1));
-                bitCount   += nbBits-1;
-            }
-            else
-            {
-                count = (short)(bitStream & (2*threshold-1));
-                if (count >= threshold) count -= max;
-                bitCount   += nbBits;
-            }
-
-            count--;   /* extra accuracy */
-            remaining -= FSE_abs(count);
-            normalizedCounter[charnum++] = count;
-            previous0 = !count;
-            while (remaining < threshold)
-            {
-                nbBits--;
-                threshold >>= 1;
-            }
-
-            {
-                if ((ip <= iend-7) || (ip + (bitCount>>3) <= iend-4))
-                {
-                    ip += bitCount>>3;
-                    bitCount &= 7;
-                }
-                else
-                {
-                    bitCount -= (int)(8 * (iend - 4 - ip));
-                    ip = iend - 4;
-                }
-                bitStream = FSE_readLE32(ip) >> (bitCount & 31);
-            }
-        }
-    }
-    if (remaining != 1) return (size_t)-FSE_ERROR_GENERIC;
-    *maxSVPtr = charnum-1;
-
-    ip += (bitCount+7)>>3;
-    if ((size_t)(ip-istart) > hbSize) return (size_t)-FSE_ERROR_srcSize_wrong;
-    return ip-istart;
-}
-
-
-/*********************************************************
-*  Decompression (Byte symbols)
-*********************************************************/
-static size_t FSE_buildDTable_rle (FSE_DTable* dt, BYTE symbolValue)
-{
-    void* ptr = dt;
-    FSE_DTableHeader* const DTableH = (FSE_DTableHeader*)ptr;
-    FSE_decode_t* const cell = (FSE_decode_t*)(ptr) + 1;   /* because dt is unsigned */
-
-    DTableH->tableLog = 0;
-    DTableH->fastMode = 0;
-
-    cell->newState = 0;
-    cell->symbol = symbolValue;
-    cell->nbBits = 0;
-
-    return 0;
-}
-
-
-static size_t FSE_buildDTable_raw (FSE_DTable* dt, unsigned nbBits)
-{
-    void* ptr = dt;
-    FSE_DTableHeader* const DTableH = (FSE_DTableHeader*)ptr;
-    FSE_decode_t* const dinfo = (FSE_decode_t*)(ptr) + 1;   /* because dt is unsigned */
-    const unsigned tableSize = 1 << nbBits;
-    const unsigned tableMask = tableSize - 1;
-    const unsigned maxSymbolValue = tableMask;
-    unsigned s;
-
-    /* Sanity checks */
-    if (nbBits < 1) return (size_t)-FSE_ERROR_GENERIC;             /* min size */
-
-    /* Build Decoding Table */
-    DTableH->tableLog = (U16)nbBits;
-    DTableH->fastMode = 1;
-    for (s=0; s<=maxSymbolValue; s++)
-    {
-        dinfo[s].newState = 0;
-        dinfo[s].symbol = (BYTE)s;
-        dinfo[s].nbBits = (BYTE)nbBits;
-    }
-
-    return 0;
-}
-
-
-/* FSE_initDStream
- * Initialize a FSE_DStream_t.
- * srcBuffer must point at the beginning of an FSE block.
- * The function result is the size of the FSE_block (== srcSize).
- * If srcSize is too small, the function will return an errorCode;
- */
-static size_t FSE_initDStream(FSE_DStream_t* bitD, const void* srcBuffer, size_t srcSize)
-{
-    if (srcSize < 1) return (size_t)-FSE_ERROR_srcSize_wrong;
-
-    if (srcSize >=  sizeof(size_t))
-    {
-        U32 contain32;
-        bitD->start = (const char*)srcBuffer;
-        bitD->ptr   = (const char*)srcBuffer + srcSize - sizeof(size_t);
-        bitD->bitContainer = FSE_readLEST(bitD->ptr);
-        contain32 = ((const BYTE*)srcBuffer)[srcSize-1];
-        if (contain32 == 0) return (size_t)-FSE_ERROR_GENERIC;   /* stop bit not present */
-        bitD->bitsConsumed = 8 - FSE_highbit32(contain32);
-    }
-    else
-    {
-        U32 contain32;
-        bitD->start = (const char*)srcBuffer;
-        bitD->ptr   = bitD->start;
-        bitD->bitContainer = *(const BYTE*)(bitD->start);
-        switch(srcSize)
-        {
-            case 7: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[6]) << (sizeof(size_t)*8 - 16);
-                    /* fallthrough */
-            case 6: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[5]) << (sizeof(size_t)*8 - 24);
-                    /* fallthrough */
-            case 5: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[4]) << (sizeof(size_t)*8 - 32);
-                    /* fallthrough */
-            case 4: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[3]) << 24;
-                    /* fallthrough */
-            case 3: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[2]) << 16;
-                    /* fallthrough */
-            case 2: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[1]) <<  8;
-                    /* fallthrough */
-            default:;
-        }
-        contain32 = ((const BYTE*)srcBuffer)[srcSize-1];
-        if (contain32 == 0) return (size_t)-FSE_ERROR_GENERIC;   /* stop bit not present */
-        bitD->bitsConsumed = 8 - FSE_highbit32(contain32);
-        bitD->bitsConsumed += (U32)(sizeof(size_t) - srcSize)*8;
-    }
-
-    return srcSize;
-}
-
-
-/*!FSE_lookBits
- * Provides next n bits from the bitContainer.
- * bitContainer is not modified (bits are still present for next read/look)
- * On 32-bits, maxNbBits==25
- * On 64-bits, maxNbBits==57
- * return : value extracted.
- */
-static size_t FSE_lookBits(FSE_DStream_t* bitD, U32 nbBits)
-{
-    const U32 bitMask = sizeof(bitD->bitContainer)*8 - 1;
-    return ((bitD->bitContainer << (bitD->bitsConsumed & bitMask)) >> 1) >> ((bitMask-nbBits) & bitMask);
-}
-
-static size_t FSE_lookBitsFast(FSE_DStream_t* bitD, U32 nbBits)   /* only if nbBits >= 1 !! */
-{
-    const U32 bitMask = sizeof(bitD->bitContainer)*8 - 1;
-    return (bitD->bitContainer << (bitD->bitsConsumed & bitMask)) >> (((bitMask+1)-nbBits) & bitMask);
-}
-
-static void FSE_skipBits(FSE_DStream_t* bitD, U32 nbBits)
-{
-    bitD->bitsConsumed += nbBits;
-}
-
-
-/*!FSE_readBits
- * Read next n bits from the bitContainer.
- * On 32-bits, don't read more than maxNbBits==25
- * On 64-bits, don't read more than maxNbBits==57
- * Use the fast variant *only* if n >= 1.
- * return : value extracted.
- */
-static size_t FSE_readBits(FSE_DStream_t* bitD, U32 nbBits)
-{
-    size_t value = FSE_lookBits(bitD, nbBits);
-    FSE_skipBits(bitD, nbBits);
-    return value;
-}
-
-static size_t FSE_readBitsFast(FSE_DStream_t* bitD, U32 nbBits)   /* only if nbBits >= 1 !! */
-{
-    size_t value = FSE_lookBitsFast(bitD, nbBits);
-    FSE_skipBits(bitD, nbBits);
-    return value;
-}
-
-static unsigned FSE_reloadDStream(FSE_DStream_t* bitD)
-{
-    if (bitD->bitsConsumed > (sizeof(bitD->bitContainer)*8))  /* should never happen */
-        return FSE_DStream_tooFar;
-
-    if (bitD->ptr >= bitD->start + sizeof(bitD->bitContainer))
-    {
-        bitD->ptr -= bitD->bitsConsumed >> 3;
-        bitD->bitsConsumed &= 7;
-        bitD->bitContainer = FSE_readLEST(bitD->ptr);
-        return FSE_DStream_unfinished;
-    }
-    if (bitD->ptr == bitD->start)
-    {
-        if (bitD->bitsConsumed < sizeof(bitD->bitContainer)*8) return FSE_DStream_endOfBuffer;
-        return FSE_DStream_completed;
-    }
-    {
-        U32 nbBytes = bitD->bitsConsumed >> 3;
-        U32 result = FSE_DStream_unfinished;
-        if (bitD->ptr - nbBytes < bitD->start)
-        {
-            nbBytes = (U32)(bitD->ptr - bitD->start);  /* ptr > start */
-            result = FSE_DStream_endOfBuffer;
-        }
-        bitD->ptr -= nbBytes;
-        bitD->bitsConsumed -= nbBytes*8;
-        bitD->bitContainer = FSE_readLEST(bitD->ptr);   /* reminder : srcSize > sizeof(bitD) */
-        return result;
-    }
-}
-
-
-static void FSE_initDState(FSE_DState_t* DStatePtr, FSE_DStream_t* bitD, const FSE_DTable* dt)
-{
-    const void* ptr = dt;
-    const FSE_DTableHeader* const DTableH = (const FSE_DTableHeader*)ptr;
-    DStatePtr->state = FSE_readBits(bitD, DTableH->tableLog);
-    FSE_reloadDStream(bitD);
-    DStatePtr->table = dt + 1;
-}
-
-static BYTE FSE_decodeSymbol(FSE_DState_t* DStatePtr, FSE_DStream_t* bitD)
-{
-    const FSE_decode_t DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
-    const U32  nbBits = DInfo.nbBits;
-    BYTE symbol = DInfo.symbol;
-    size_t lowBits = FSE_readBits(bitD, nbBits);
-
-    DStatePtr->state = DInfo.newState + lowBits;
-    return symbol;
-}
-
-static BYTE FSE_decodeSymbolFast(FSE_DState_t* DStatePtr, FSE_DStream_t* bitD)
-{
-    const FSE_decode_t DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
-    const U32 nbBits = DInfo.nbBits;
-    BYTE symbol = DInfo.symbol;
-    size_t lowBits = FSE_readBitsFast(bitD, nbBits);
-
-    DStatePtr->state = DInfo.newState + lowBits;
-    return symbol;
-}
-
-/* FSE_endOfDStream
-   Tells if bitD has reached end of bitStream or not */
-
-static unsigned FSE_endOfDStream(const FSE_DStream_t* bitD)
-{
-    return ((bitD->ptr == bitD->start) && (bitD->bitsConsumed == sizeof(bitD->bitContainer)*8));
-}
-
-static unsigned FSE_endOfDState(const FSE_DState_t* DStatePtr)
-{
-    return DStatePtr->state == 0;
-}
-
-
-FORCE_INLINE size_t FSE_decompress_usingDTable_generic(
-          void* dst, size_t maxDstSize,
-    const void* cSrc, size_t cSrcSize,
-    const FSE_DTable* dt, const unsigned fast)
-{
-    BYTE* const ostart = (BYTE*) dst;
-    BYTE* op = ostart;
-    BYTE* const omax = op + maxDstSize;
-    BYTE* const olimit = omax-3;
-
-    FSE_DStream_t bitD;
-    FSE_DState_t state1;
-    FSE_DState_t state2;
-    size_t errorCode;
-
-    /* Init */
-    errorCode = FSE_initDStream(&bitD, cSrc, cSrcSize);   /* replaced last arg by maxCompressed Size */
-    if (FSE_isError(errorCode)) return errorCode;
-
-    FSE_initDState(&state1, &bitD, dt);
-    FSE_initDState(&state2, &bitD, dt);
-
-#define FSE_GETSYMBOL(statePtr) fast ? FSE_decodeSymbolFast(statePtr, &bitD) : FSE_decodeSymbol(statePtr, &bitD)
-
-    /* 4 symbols per loop */
-    for ( ; (FSE_reloadDStream(&bitD)==FSE_DStream_unfinished) && (op<olimit) ; op+=4)
-    {
-        op[0] = FSE_GETSYMBOL(&state1);
-
-        if (FSE_MAX_TABLELOG*2+7 > sizeof(bitD.bitContainer)*8)    /* This test must be static */
-            FSE_reloadDStream(&bitD);
-
-        op[1] = FSE_GETSYMBOL(&state2);
-
-        if (FSE_MAX_TABLELOG*4+7 > sizeof(bitD.bitContainer)*8)    /* This test must be static */
-            { if (FSE_reloadDStream(&bitD) > FSE_DStream_unfinished) { op+=2; break; } }
-
-        op[2] = FSE_GETSYMBOL(&state1);
-
-        if (FSE_MAX_TABLELOG*2+7 > sizeof(bitD.bitContainer)*8)    /* This test must be static */
-            FSE_reloadDStream(&bitD);
-
-        op[3] = FSE_GETSYMBOL(&state2);
-    }
-
-    /* tail */
-    /* note : FSE_reloadDStream(&bitD) >= FSE_DStream_partiallyFilled; Ends at exactly FSE_DStream_completed */
-    while (1)
-    {
-        if ( (FSE_reloadDStream(&bitD)>FSE_DStream_completed) || (op==omax) || (FSE_endOfDStream(&bitD) && (fast || FSE_endOfDState(&state1))) )
-            break;
-
-        *op++ = FSE_GETSYMBOL(&state1);
-
-        if ( (FSE_reloadDStream(&bitD)>FSE_DStream_completed) || (op==omax) || (FSE_endOfDStream(&bitD) && (fast || FSE_endOfDState(&state2))) )
-            break;
-
-        *op++ = FSE_GETSYMBOL(&state2);
-    }
-
-    /* end ? */
-    if (FSE_endOfDStream(&bitD) && FSE_endOfDState(&state1) && FSE_endOfDState(&state2))
-        return op-ostart;
-
-    if (op==omax) return (size_t)-FSE_ERROR_dstSize_tooSmall;   /* dst buffer is full, but cSrc unfinished */
-
-    return (size_t)-FSE_ERROR_corruptionDetected;
-}
-
-
-static size_t FSE_decompress_usingDTable(void* dst, size_t originalSize,
-                            const void* cSrc, size_t cSrcSize,
-                            const FSE_DTable* dt)
-{
-    FSE_DTableHeader DTableH;
-    memcpy(&DTableH, dt, sizeof(DTableH));   /* memcpy() into local variable, to avoid strict aliasing warning */
-
-    /* select fast mode (static) */
-    if (DTableH.fastMode) return FSE_decompress_usingDTable_generic(dst, originalSize, cSrc, cSrcSize, dt, 1);
-    return FSE_decompress_usingDTable_generic(dst, originalSize, cSrc, cSrcSize, dt, 0);
-}
-
-
-static size_t FSE_decompress(void* dst, size_t maxDstSize, const void* cSrc, size_t cSrcSize)
-{
-    const BYTE* const istart = (const BYTE*)cSrc;
-    const BYTE* ip = istart;
-    short counting[FSE_MAX_SYMBOL_VALUE+1];
-    DTable_max_t dt;   /* Static analyzer seems unable to understand this table will be properly initialized later */
-    unsigned tableLog;
-    unsigned maxSymbolValue = FSE_MAX_SYMBOL_VALUE;
-    size_t errorCode;
-
-    if (cSrcSize<2) return (size_t)-FSE_ERROR_srcSize_wrong;   /* too small input size */
-
-    /* normal FSE decoding mode */
-    errorCode = FSE_readNCount (counting, &maxSymbolValue, &tableLog, istart, cSrcSize);
-    if (FSE_isError(errorCode)) return errorCode;
-    if (errorCode >= cSrcSize) return (size_t)-FSE_ERROR_srcSize_wrong;   /* too small input size */
-    ip += errorCode;
-    cSrcSize -= errorCode;
-
-    errorCode = FSE_buildDTable (dt, counting, maxSymbolValue, tableLog);
-    if (FSE_isError(errorCode)) return errorCode;
-
-    /* always return, even if it is an error code */
-    return FSE_decompress_usingDTable (dst, maxDstSize, ip, cSrcSize, dt);
-}
-
-
-
-/* *******************************************************
-*  Huff0 : Huffman block compression
-*********************************************************/
-#define HUF_MAX_SYMBOL_VALUE 255
-#define HUF_DEFAULT_TABLELOG  12       /* used by default, when not specified */
-#define HUF_MAX_TABLELOG  12           /* max possible tableLog; for allocation purpose; can be modified */
-#define HUF_ABSOLUTEMAX_TABLELOG  16   /* absolute limit of HUF_MAX_TABLELOG. Beyond that value, code does not work */
-#if (HUF_MAX_TABLELOG > HUF_ABSOLUTEMAX_TABLELOG)
-#  error "HUF_MAX_TABLELOG is too large !"
-#endif
-
-typedef struct HUF_CElt_s {
-  U16  val;
-  BYTE nbBits;
-} HUF_CElt ;
-
-typedef struct nodeElt_s {
-    U32 count;
-    U16 parent;
-    BYTE byte;
-    BYTE nbBits;
-} nodeElt;
-
-
-/* *******************************************************
-*  Huff0 : Huffman block decompression
-*********************************************************/
-typedef struct {
-    BYTE byte;
-    BYTE nbBits;
-} HUF_DElt;
-
-static size_t HUF_readDTable (U16* DTable, const void* src, size_t srcSize)
-{
-    BYTE huffWeight[HUF_MAX_SYMBOL_VALUE + 1];
-    U32 rankVal[HUF_ABSOLUTEMAX_TABLELOG + 1];  /* large enough for values from 0 to 16 */
-    U32 weightTotal;
-    U32 maxBits;
-    const BYTE* ip = (const BYTE*) src;
-    size_t iSize;
-    size_t oSize;
-    U32 n;
-    U32 nextRankStart;
-    void* ptr = DTable+1;
-    HUF_DElt* const dt = (HUF_DElt*)ptr;
-
-    if (!srcSize) return (size_t)-FSE_ERROR_srcSize_wrong;
-    iSize = ip[0];
-
-    FSE_STATIC_ASSERT(sizeof(HUF_DElt) == sizeof(U16));   /* if compilation fails here, assertion is false */
-    //memset(huffWeight, 0, sizeof(huffWeight));   /* should not be necessary, but some analyzer complain ... */
-    if (iSize >= 128)  /* special header */
-    {
-        if (iSize >= (242))   /* RLE */
-        {
-            static int l[14] = { 1, 2, 3, 4, 7, 8, 15, 16, 31, 32, 63, 64, 127, 128 };
-            oSize = l[iSize-242];
-            memset(huffWeight, 1, sizeof(huffWeight));
-            iSize = 0;
-        }
-        else   /* Incompressible */
-        {
-            oSize = iSize - 127;
-            iSize = ((oSize+1)/2);
-            if (iSize+1 > srcSize) return (size_t)-FSE_ERROR_srcSize_wrong;
-            ip += 1;
-            for (n=0; n<oSize; n+=2)
-            {
-                huffWeight[n]   = ip[n/2] >> 4;
-                huffWeight[n+1] = ip[n/2] & 15;
-            }
-        }
-    }
-    else  /* header compressed with FSE (normal case) */
-    {
-        if (iSize+1 > srcSize) return (size_t)-FSE_ERROR_srcSize_wrong;
-        oSize = FSE_decompress(huffWeight, HUF_MAX_SYMBOL_VALUE, ip+1, iSize);   /* max 255 values decoded, last one is implied */
-        if (FSE_isError(oSize)) return oSize;
-    }
-
-    /* collect weight stats */
-    memset(rankVal, 0, sizeof(rankVal));
-    weightTotal = 0;
-    for (n=0; n<oSize; n++)
-    {
-        if (huffWeight[n] >= HUF_ABSOLUTEMAX_TABLELOG) return (size_t)-FSE_ERROR_corruptionDetected;
-        rankVal[huffWeight[n]]++;
-        weightTotal += (1 << huffWeight[n]) >> 1;
-    }
-    if (weightTotal == 0) return (size_t)-FSE_ERROR_corruptionDetected;
-
-    /* get last non-null symbol weight (implied, total must be 2^n) */
-    maxBits = FSE_highbit32(weightTotal) + 1;
-    if (maxBits > DTable[0]) return (size_t)-FSE_ERROR_tableLog_tooLarge;   /* DTable is too small */
-    DTable[0] = (U16)maxBits;
-    {
-        U32 total = 1 << maxBits;
-        U32 rest = total - weightTotal;
-        U32 verif = 1 << FSE_highbit32(rest);
-        U32 lastWeight = FSE_highbit32(rest) + 1;
-        if (verif != rest) return (size_t)-FSE_ERROR_corruptionDetected;    /* last value must be a clean power of 2 */
-        huffWeight[oSize] = (BYTE)lastWeight;
-        rankVal[lastWeight]++;
-    }
-
-    /* check tree construction validity */
-    if ((rankVal[1] < 2) || (rankVal[1] & 1)) return (size_t)-FSE_ERROR_corruptionDetected;   /* by construction : at least 2 elts of rank 1, must be even */
-
-    /* Prepare ranks */
-    nextRankStart = 0;
-    for (n=1; n<=maxBits; n++)
-    {
-        U32 current = nextRankStart;
-        nextRankStart += (rankVal[n] << (n-1));
-        rankVal[n] = current;
-    }
-
-    /* fill DTable */
-    for (n=0; n<=oSize; n++)
-    {
-        const U32 w = huffWeight[n];
-        const U32 length = (1 << w) >> 1;
-        U32 i;
-        HUF_DElt D;
-        D.byte = (BYTE)n; D.nbBits = (BYTE)(maxBits + 1 - w);
-        for (i = rankVal[w]; i < rankVal[w] + length; i++)
-            dt[i] = D;
-        rankVal[w] += length;
-    }
-
-    return iSize+1;
-}
-
-
-static BYTE HUF_decodeSymbol(FSE_DStream_t* Dstream, const HUF_DElt* dt, const U32 dtLog)
-{
-        const size_t val = FSE_lookBitsFast(Dstream, dtLog); /* note : dtLog >= 1 */
-        const BYTE c = dt[val].byte;
-        FSE_skipBits(Dstream, dt[val].nbBits);
-        return c;
-}
-
-static size_t HUF_decompress_usingDTable(   /* -3% slower when non static */
-          void* dst, size_t maxDstSize,
-    const void* cSrc, size_t cSrcSize,
-    const U16* DTable)
-{
-    if (cSrcSize < 6) return (size_t)-FSE_ERROR_srcSize_wrong;
-    {
-        BYTE* const ostart = (BYTE*) dst;
-        BYTE* op = ostart;
-        BYTE* const omax = op + maxDstSize;
-        BYTE* const olimit = maxDstSize < 15 ? op : omax-15;
-
-        const void* ptr = DTable;
-        const HUF_DElt* const dt = (const HUF_DElt*)(ptr)+1;
-        const U32 dtLog = DTable[0];
-        size_t errorCode;
-        U32 reloadStatus;
-
-        /* Init */
-
-        const U16* jumpTable = (const U16*)cSrc;
-        const size_t length1 = FSE_readLE16(jumpTable);
-        const size_t length2 = FSE_readLE16(jumpTable+1);
-        const size_t length3 = FSE_readLE16(jumpTable+2);
-        const size_t length4 = cSrcSize - 6 - length1 - length2 - length3;   /* check coherency !! */
-        const char* const start1 = (const char*)(cSrc) + 6;
-        const char* const start2 = start1 + length1;
-        const char* const start3 = start2 + length2;
-        const char* const start4 = start3 + length3;
-        FSE_DStream_t bitD1, bitD2, bitD3, bitD4;
-
-        if (length1+length2+length3+6 >= cSrcSize) return (size_t)-FSE_ERROR_srcSize_wrong;
-
-        errorCode = FSE_initDStream(&bitD1, start1, length1);
-        if (FSE_isError(errorCode)) return errorCode;
-        errorCode = FSE_initDStream(&bitD2, start2, length2);
-        if (FSE_isError(errorCode)) return errorCode;
-        errorCode = FSE_initDStream(&bitD3, start3, length3);
-        if (FSE_isError(errorCode)) return errorCode;
-        errorCode = FSE_initDStream(&bitD4, start4, length4);
-        if (FSE_isError(errorCode)) return errorCode;
-
-        reloadStatus=FSE_reloadDStream(&bitD2);
-
-        /* 16 symbols per loop */
-        for ( ; (reloadStatus<FSE_DStream_completed) && (op<olimit);  /* D2-3-4 are supposed to be synchronized and finish together */
-            op+=16, reloadStatus = FSE_reloadDStream(&bitD2) | FSE_reloadDStream(&bitD3) | FSE_reloadDStream(&bitD4), FSE_reloadDStream(&bitD1))
-        {
-    #define HUF_DECODE_SYMBOL_0(n, Dstream) \
-            op[n] = HUF_decodeSymbol(&Dstream, dt, dtLog);
-
-    #define HUF_DECODE_SYMBOL_1(n, Dstream) \
-            op[n] = HUF_decodeSymbol(&Dstream, dt, dtLog); \
-            if (FSE_32bits() && (HUF_MAX_TABLELOG>12)) FSE_reloadDStream(&Dstream)
-
-    #define HUF_DECODE_SYMBOL_2(n, Dstream) \
-            op[n] = HUF_decodeSymbol(&Dstream, dt, dtLog); \
-            if (FSE_32bits()) FSE_reloadDStream(&Dstream)
-
-            HUF_DECODE_SYMBOL_1( 0, bitD1);
-            HUF_DECODE_SYMBOL_1( 1, bitD2);
-            HUF_DECODE_SYMBOL_1( 2, bitD3);
-            HUF_DECODE_SYMBOL_1( 3, bitD4);
-            HUF_DECODE_SYMBOL_2( 4, bitD1);
-            HUF_DECODE_SYMBOL_2( 5, bitD2);
-            HUF_DECODE_SYMBOL_2( 6, bitD3);
-            HUF_DECODE_SYMBOL_2( 7, bitD4);
-            HUF_DECODE_SYMBOL_1( 8, bitD1);
-            HUF_DECODE_SYMBOL_1( 9, bitD2);
-            HUF_DECODE_SYMBOL_1(10, bitD3);
-            HUF_DECODE_SYMBOL_1(11, bitD4);
-            HUF_DECODE_SYMBOL_0(12, bitD1);
-            HUF_DECODE_SYMBOL_0(13, bitD2);
-            HUF_DECODE_SYMBOL_0(14, bitD3);
-            HUF_DECODE_SYMBOL_0(15, bitD4);
-        }
-
-        if (reloadStatus!=FSE_DStream_completed)   /* not complete : some bitStream might be FSE_DStream_unfinished */
-            return (size_t)-FSE_ERROR_corruptionDetected;
-
-        /* tail */
-        {
-            /* bitTail = bitD1; */   /* *much* slower : -20% !??! */
-            FSE_DStream_t bitTail;
-            bitTail.ptr = bitD1.ptr;
-            bitTail.bitsConsumed = bitD1.bitsConsumed;
-            bitTail.bitContainer = bitD1.bitContainer;   /* required in case of FSE_DStream_endOfBuffer */
-            bitTail.start = start1;
-            for ( ; (FSE_reloadDStream(&bitTail) < FSE_DStream_completed) && (op<omax) ; op++)
-            {
-                HUF_DECODE_SYMBOL_0(0, bitTail);
-            }
-
-            if (FSE_endOfDStream(&bitTail))
-                return op-ostart;
-        }
-
-        if (op==omax) return (size_t)-FSE_ERROR_dstSize_tooSmall;   /* dst buffer is full, but cSrc unfinished */
-
-        return (size_t)-FSE_ERROR_corruptionDetected;
-    }
-}
-
-
-static size_t HUF_decompress (void* dst, size_t maxDstSize, const void* cSrc, size_t cSrcSize)
-{
-    HUF_CREATE_STATIC_DTABLE(DTable, HUF_MAX_TABLELOG);
-    const BYTE* ip = (const BYTE*) cSrc;
-    size_t errorCode;
-
-    errorCode = HUF_readDTable (DTable, cSrc, cSrcSize);
-    if (FSE_isError(errorCode)) return errorCode;
-    if (errorCode >= cSrcSize) return (size_t)-FSE_ERROR_srcSize_wrong;
-    ip += errorCode;
-    cSrcSize -= errorCode;
-
-    return HUF_decompress_usingDTable (dst, maxDstSize, ip, cSrcSize, DTable);
-}
-
-
-#endif   /* FSE_COMMONDEFS_ONLY */
-
-/*
-    zstd - standard compression library
-    Copyright (C) 2014-2015, Yann Collet.
-
-    BSD 2-Clause License (https://opensource.org/licenses/bsd-license.php)
-
-    Redistribution and use in source and binary forms, with or without
-    modification, are permitted provided that the following conditions are
-    met:
-    * Redistributions of source code must retain the above copyright
-    notice, this list of conditions and the following disclaimer.
-    * Redistributions in binary form must reproduce the above
-    copyright notice, this list of conditions and the following disclaimer
-    in the documentation and/or other materials provided with the
-    distribution.
-    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-    A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-    OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-    SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-    LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-    You can contact the author at :
-    - zstd source repository : https://github.com/Cyan4973/zstd
-    - ztsd public forum : https://groups.google.com/forum/#!forum/lz4c
-*/
-
-/****************************************************************
-*  Tuning parameters
-*****************************************************************/
-/* MEMORY_USAGE :
-*  Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; etc.)
-*  Increasing memory usage improves compression ratio
-*  Reduced memory usage can improve speed, due to cache effect */
-#define ZSTD_MEMORY_USAGE 17
-
-
-/**************************************
-   CPU Feature Detection
-**************************************/
-/*
- * Automated efficient unaligned memory access detection
- * Based on known hardware architectures
- * This list will be updated thanks to feedbacks
- */
-#if defined(CPU_HAS_EFFICIENT_UNALIGNED_MEMORY_ACCESS) \
-    || defined(__ARM_FEATURE_UNALIGNED) \
-    || defined(__i386__) || defined(__x86_64__) \
-    || defined(_M_IX86) || defined(_M_X64) \
-    || defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_8__) \
-    || (defined(_M_ARM) && (_M_ARM >= 7))
-#  define ZSTD_UNALIGNED_ACCESS 1
-#else
-#  define ZSTD_UNALIGNED_ACCESS 0
-#endif
-
-
-/********************************************************
-*  Includes
-*********************************************************/
-#include <stdlib.h>      /* calloc */
-#include <string.h>      /* memcpy, memmove */
-#include <stdio.h>       /* debug : printf */
-
-
-/********************************************************
-*  Compiler specifics
-*********************************************************/
-#ifdef __AVX2__
-#  include <immintrin.h>   /* AVX2 intrinsics */
-#endif
-
-#ifdef _MSC_VER    /* Visual Studio */
-#  include <intrin.h>                    /* For Visual 2005 */
-#  pragma warning(disable : 4127)        /* disable: C4127: conditional expression is constant */
-#  pragma warning(disable : 4324)        /* disable: C4324: padded structure */
-#endif
-
-
-#ifndef MEM_ACCESS_MODULE
-#define MEM_ACCESS_MODULE
-/********************************************************
-*  Basic Types
-*********************************************************/
-#if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L   /* C99 */
-# if defined(_AIX)
-#  include <inttypes.h>
-# else
-#  include <stdint.h> /* intptr_t */
-# endif
-typedef  uint8_t BYTE;
-typedef uint16_t U16;
-typedef  int16_t S16;
-typedef uint32_t U32;
-typedef  int32_t S32;
-typedef uint64_t U64;
-#else
-typedef unsigned char       BYTE;
-typedef unsigned short      U16;
-typedef   signed short      S16;
-typedef unsigned int        U32;
-typedef   signed int        S32;
-typedef unsigned long long  U64;
-#endif
-
-#endif   /* MEM_ACCESS_MODULE */
-
-
-/********************************************************
-*  Constants
-*********************************************************/
-static const U32 ZSTD_magicNumber = 0xFD2FB51E;   /* 3rd version : seqNb header */
-
-#define HASH_LOG (ZSTD_MEMORY_USAGE - 2)
-#define HASH_TABLESIZE (1 << HASH_LOG)
-#define HASH_MASK (HASH_TABLESIZE - 1)
-
-#define KNUTH 2654435761
-
-#define BIT7 128
-#define BIT6  64
-#define BIT5  32
-#define BIT4  16
-
-#define KB *(1 <<10)
-#define MB *(1 <<20)
-#define GB *(1U<<30)
-
-#define BLOCKSIZE (128 KB)                 /* define, for static allocation */
-
-#define WORKPLACESIZE (BLOCKSIZE*3)
-#define MINMATCH 4
-#define MLbits   7
-#define LLbits   6
-#define Offbits  5
-#define MaxML  ((1<<MLbits )-1)
-#define MaxLL  ((1<<LLbits )-1)
-#define MaxOff ((1<<Offbits)-1)
-#define LitFSELog  11
-#define MLFSELog   10
-#define LLFSELog   10
-#define OffFSELog   9
-#define MAX(a,b) ((a)<(b)?(b):(a))
-#define MaxSeq MAX(MaxLL, MaxML)
-
-#define LITERAL_NOENTROPY 63
-#define COMMAND_NOENTROPY 7   /* to remove */
-
-#define ZSTD_CONTENTSIZE_ERROR   (0ULL - 2)
-
-static const size_t ZSTD_blockHeaderSize = 3;
-static const size_t ZSTD_frameHeaderSize = 4;
-
-
-/********************************************************
-*  Memory operations
-*********************************************************/
-static unsigned ZSTD_32bits(void) { return sizeof(void*)==4; }
-
-static unsigned ZSTD_isLittleEndian(void)
-{
-    const union { U32 i; BYTE c[4]; } one = { 1 };   /* don't use static : performance detrimental  */
-    return one.c[0];
-}
-
-static U16    ZSTD_read16(const void* p) { U16 r; memcpy(&r, p, sizeof(r)); return r; }
-
-static void   ZSTD_copy4(void* dst, const void* src) { memcpy(dst, src, 4); }
-
-static void   ZSTD_copy8(void* dst, const void* src) { memcpy(dst, src, 8); }
-
-#define COPY8(d,s)    { ZSTD_copy8(d,s); d+=8; s+=8; }
-
-static void ZSTD_wildcopy(void* dst, const void* src, ptrdiff_t length)
-{
-    const BYTE* ip = (const BYTE*)src;
-    BYTE* op = (BYTE*)dst;
-    BYTE* const oend = op + length;
-    while (op < oend) COPY8(op, ip);
-}
-
-static U16 ZSTD_readLE16(const void* memPtr)
-{
-    if (ZSTD_isLittleEndian()) return ZSTD_read16(memPtr);
-    else
-    {
-        const BYTE* p = (const BYTE*)memPtr;
-        return (U16)((U16)p[0] + ((U16)p[1]<<8));
-    }
-}
-
-static U32 ZSTD_readLE24(const void* memPtr)
-{
-    return ZSTD_readLE16(memPtr) + (((const BYTE*)memPtr)[2] << 16);
-}
-
-static U32 ZSTD_readBE32(const void* memPtr)
-{
-    const BYTE* p = (const BYTE*)memPtr;
-    return (U32)(((U32)p[0]<<24) + ((U32)p[1]<<16) + ((U32)p[2]<<8) + ((U32)p[3]<<0));
-}
-
-
-/**************************************
-*  Local structures
-***************************************/
-typedef struct ZSTD_Cctx_s ZSTD_Cctx;
-
-typedef enum { bt_compressed, bt_raw, bt_rle, bt_end } blockType_t;
-
-typedef struct
-{
-    blockType_t blockType;
-    U32 origSize;
-} blockProperties_t;
-
-typedef struct {
-    void* buffer;
-    U32*  offsetStart;
-    U32*  offset;
-    BYTE* offCodeStart;
-    BYTE* offCode;
-    BYTE* litStart;
-    BYTE* lit;
-    BYTE* litLengthStart;
-    BYTE* litLength;
-    BYTE* matchLengthStart;
-    BYTE* matchLength;
-    BYTE* dumpsStart;
-    BYTE* dumps;
-} SeqStore_t;
-
-
-typedef struct ZSTD_Cctx_s
-{
-    const BYTE* base;
-    U32 current;
-    U32 nextUpdate;
-    SeqStore_t seqStore;
-#ifdef __AVX2__
-    __m256i hashTable[HASH_TABLESIZE>>3];
-#else
-    U32 hashTable[HASH_TABLESIZE];
-#endif
-    BYTE buffer[WORKPLACESIZE];
-} cctxi_t;
-
-
-
-
-/**************************************
-*  Error Management
-**************************************/
-/* published entry point */
-unsigned ZSTDv01_isError(size_t code) { return ERR_isError(code); }
-
-
-/**************************************
-*  Tool functions
-**************************************/
-#define ZSTD_VERSION_MAJOR    0    /* for breaking interface changes  */
-#define ZSTD_VERSION_MINOR    1    /* for new (non-breaking) interface capabilities */
-#define ZSTD_VERSION_RELEASE  3    /* for tweaks, bug-fixes, or development */
-#define ZSTD_VERSION_NUMBER  (ZSTD_VERSION_MAJOR *100*100 + ZSTD_VERSION_MINOR *100 + ZSTD_VERSION_RELEASE)
-
-/**************************************************************
-*   Decompression code
-**************************************************************/
-
-static size_t ZSTDv01_getcBlockSize(const void* src, size_t srcSize, blockProperties_t* bpPtr)
-{
-    const BYTE* const in = (const BYTE* const)src;
-    BYTE headerFlags;
-    U32 cSize;
-
-    if (srcSize < 3) return ERROR(srcSize_wrong);
-
-    headerFlags = *in;
-    cSize = in[2] + (in[1]<<8) + ((in[0] & 7)<<16);
-
-    bpPtr->blockType = (blockType_t)(headerFlags >> 6);
-    bpPtr->origSize = (bpPtr->blockType == bt_rle) ? cSize : 0;
-
-    if (bpPtr->blockType == bt_end) return 0;
-    if (bpPtr->blockType == bt_rle) return 1;
-    return cSize;
-}
-
-
-static size_t ZSTD_copyUncompressedBlock(void* dst, size_t maxDstSize, const void* src, size_t srcSize)
-{
-    if (srcSize > maxDstSize) return ERROR(dstSize_tooSmall);
-    if (srcSize > 0) {
-        memcpy(dst, src, srcSize);
-    }
-    return srcSize;
-}
-
-
-static size_t ZSTD_decompressLiterals(void* ctx,
-                                      void* dst, size_t maxDstSize,
-                                const void* src, size_t srcSize)
-{
-    BYTE* op = (BYTE*)dst;
-    BYTE* const oend = op + maxDstSize;
-    const BYTE* ip = (const BYTE*)src;
-    size_t errorCode;
-    size_t litSize;
-
-    /* check : minimum 2, for litSize, +1, for content */
-    if (srcSize <= 3) return ERROR(corruption_detected);
-
-    litSize = ip[1] + (ip[0]<<8);
-    litSize += ((ip[-3] >> 3) & 7) << 16;   /* mmmmh.... */
-    op = oend - litSize;
-
-    (void)ctx;
-    if (litSize > maxDstSize) return ERROR(dstSize_tooSmall);
-    errorCode = HUF_decompress(op, litSize, ip+2, srcSize-2);
-    if (FSE_isError(errorCode)) return ERROR(GENERIC);
-    return litSize;
-}
-
-
-static size_t ZSTDv01_decodeLiteralsBlock(void* ctx,
-                                void* dst, size_t maxDstSize,
-                          const BYTE** litStart, size_t* litSize,
-                          const void* src, size_t srcSize)
-{
-    const BYTE* const istart = (const BYTE* const)src;
-    const BYTE* ip = istart;
-    BYTE* const ostart = (BYTE* const)dst;
-    BYTE* const oend = ostart + maxDstSize;
-    blockProperties_t litbp;
-
-    size_t litcSize = ZSTDv01_getcBlockSize(src, srcSize, &litbp);
-    if (ZSTDv01_isError(litcSize)) return litcSize;
-    if (litcSize > srcSize - ZSTD_blockHeaderSize) return ERROR(srcSize_wrong);
-    ip += ZSTD_blockHeaderSize;
-
-    switch(litbp.blockType)
-    {
-    case bt_raw:
-        *litStart = ip;
-        ip += litcSize;
-        *litSize = litcSize;
-        break;
-    case bt_rle:
-        {
-            size_t rleSize = litbp.origSize;
-            if (rleSize>maxDstSize) return ERROR(dstSize_tooSmall);
-            if (!srcSize) return ERROR(srcSize_wrong);
-            if (rleSize > 0) {
-                memset(oend - rleSize, *ip, rleSize);
-            }
-            *litStart = oend - rleSize;
-            *litSize = rleSize;
-            ip++;
-            break;
-        }
-    case bt_compressed:
-        {
-            size_t decodedLitSize = ZSTD_decompressLiterals(ctx, dst, maxDstSize, ip, litcSize);
-            if (ZSTDv01_isError(decodedLitSize)) return decodedLitSize;
-            *litStart = oend - decodedLitSize;
-            *litSize = decodedLitSize;
-            ip += litcSize;
-            break;
-        }
-    case bt_end:
-    default:
-        return ERROR(GENERIC);
-    }
-
-    return ip-istart;
-}
-
-
-static size_t ZSTDv01_decodeSeqHeaders(int* nbSeq, const BYTE** dumpsPtr, size_t* dumpsLengthPtr,
-                         FSE_DTable* DTableLL, FSE_DTable* DTableML, FSE_DTable* DTableOffb,
-                         const void* src, size_t srcSize)
-{
-    const BYTE* const istart = (const BYTE* const)src;
-    const BYTE* ip = istart;
-    const BYTE* const iend = istart + srcSize;
-    U32 LLtype, Offtype, MLtype;
-    U32 LLlog, Offlog, MLlog;
-    size_t dumpsLength;
-
-    /* check */
-    if (srcSize < 5) return ERROR(srcSize_wrong);
-
-    /* SeqHead */
-    *nbSeq = ZSTD_readLE16(ip); ip+=2;
-    LLtype  = *ip >> 6;
-    Offtype = (*ip >> 4) & 3;
-    MLtype  = (*ip >> 2) & 3;
-    if (*ip & 2)
-    {
-        dumpsLength  = ip[2];
-        dumpsLength += ip[1] << 8;
-        ip += 3;
-    }
-    else
-    {
-        dumpsLength  = ip[1];
-        dumpsLength += (ip[0] & 1) << 8;
-        ip += 2;
-    }
-    *dumpsPtr = ip;
-    ip += dumpsLength;
-    *dumpsLengthPtr = dumpsLength;
-
-    /* check */
-    if (ip > iend-3) return ERROR(srcSize_wrong); /* min : all 3 are "raw", hence no header, but at least xxLog bits per type */
-
-    /* sequences */
-    {
-        S16 norm[MaxML+1];    /* assumption : MaxML >= MaxLL and MaxOff */
-        size_t headerSize;
-
-        /* Build DTables */
-        switch(LLtype)
-        {
-        case bt_rle :
-            LLlog = 0;
-            FSE_buildDTable_rle(DTableLL, *ip++); break;
-        case bt_raw :
-            LLlog = LLbits;
-            FSE_buildDTable_raw(DTableLL, LLbits); break;
-        default :
-            {   U32 max = MaxLL;
-                headerSize = FSE_readNCount(norm, &max, &LLlog, ip, iend-ip);
-                if (FSE_isError(headerSize)) return ERROR(GENERIC);
-                if (LLlog > LLFSELog) return ERROR(corruption_detected);
-                ip += headerSize;
-                FSE_buildDTable(DTableLL, norm, max, LLlog);
-        }   }
-
-        switch(Offtype)
-        {
-        case bt_rle :
-            Offlog = 0;
-            if (ip > iend-2) return ERROR(srcSize_wrong); /* min : "raw", hence no header, but at least xxLog bits */
-            FSE_buildDTable_rle(DTableOffb, *ip++); break;
-        case bt_raw :
-            Offlog = Offbits;
-            FSE_buildDTable_raw(DTableOffb, Offbits); break;
-        default :
-            {   U32 max = MaxOff;
-                headerSize = FSE_readNCount(norm, &max, &Offlog, ip, iend-ip);
-                if (FSE_isError(headerSize)) return ERROR(GENERIC);
-                if (Offlog > OffFSELog) return ERROR(corruption_detected);
-                ip += headerSize;
-                FSE_buildDTable(DTableOffb, norm, max, Offlog);
-        }   }
-
-        switch(MLtype)
-        {
-        case bt_rle :
-            MLlog = 0;
-            if (ip > iend-2) return ERROR(srcSize_wrong); /* min : "raw", hence no header, but at least xxLog bits */
-            FSE_buildDTable_rle(DTableML, *ip++); break;
-        case bt_raw :
-            MLlog = MLbits;
-            FSE_buildDTable_raw(DTableML, MLbits); break;
-        default :
-            {   U32 max = MaxML;
-                headerSize = FSE_readNCount(norm, &max, &MLlog, ip, iend-ip);
-                if (FSE_isError(headerSize)) return ERROR(GENERIC);
-                if (MLlog > MLFSELog) return ERROR(corruption_detected);
-                ip += headerSize;
-                FSE_buildDTable(DTableML, norm, max, MLlog);
-    }   }   }
-
-    return ip-istart;
-}
-
-
-typedef struct {
-    size_t litLength;
-    size_t offset;
-    size_t matchLength;
-} seq_t;
-
-typedef struct {
-    FSE_DStream_t DStream;
-    FSE_DState_t stateLL;
-    FSE_DState_t stateOffb;
-    FSE_DState_t stateML;
-    size_t prevOffset;
-    const BYTE* dumps;
-    const BYTE* dumpsEnd;
-} seqState_t;
-
-
-static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState)
-{
-    size_t litLength;
-    size_t prevOffset;
-    size_t offset;
-    size_t matchLength;
-    const BYTE* dumps = seqState->dumps;
-    const BYTE* const de = seqState->dumpsEnd;
-
-    /* Literal length */
-    litLength = FSE_decodeSymbol(&(seqState->stateLL), &(seqState->DStream));
-    prevOffset = litLength ? seq->offset : seqState->prevOffset;
-    seqState->prevOffset = seq->offset;
-    if (litLength == MaxLL)
-    {
-        const U32 add = dumps<de ? *dumps++ : 0;
-        if (add < 255) litLength += add;
-        else
-        {
-            if (dumps<=(de-3))
-            {
-                litLength = ZSTD_readLE24(dumps);
-                dumps += 3;
-            }
-        }
-    }
-
-    /* Offset */
-    {
-        U32 offsetCode, nbBits;
-        offsetCode = FSE_decodeSymbol(&(seqState->stateOffb), &(seqState->DStream));
-        if (ZSTD_32bits()) FSE_reloadDStream(&(seqState->DStream));
-        nbBits = offsetCode - 1;
-        if (offsetCode==0) nbBits = 0;   /* cmove */
-        offset = ((size_t)1 << (nbBits & ((sizeof(offset)*8)-1))) + FSE_readBits(&(seqState->DStream), nbBits);
-        if (ZSTD_32bits()) FSE_reloadDStream(&(seqState->DStream));
-        if (offsetCode==0) offset = prevOffset;
-    }
-
-    /* MatchLength */
-    matchLength = FSE_decodeSymbol(&(seqState->stateML), &(seqState->DStream));
-    if (matchLength == MaxML)
-    {
-        const U32 add = dumps<de ? *dumps++ : 0;
-        if (add < 255) matchLength += add;
-        else
-        {
-            if (dumps<=(de-3))
-            {
-                matchLength = ZSTD_readLE24(dumps);
-                dumps += 3;
-            }
-        }
-    }
-    matchLength += MINMATCH;
-
-    /* save result */
-    seq->litLength = litLength;
-    seq->offset = offset;
-    seq->matchLength = matchLength;
-    seqState->dumps = dumps;
-}
-
-
-static size_t ZSTD_execSequence(BYTE* op,
-                                seq_t sequence,
-                                const BYTE** litPtr, const BYTE* const litLimit,
-                                BYTE* const base, BYTE* const oend)
-{
-    static const int dec32table[] = {0, 1, 2, 1, 4, 4, 4, 4};   /* added */
-    static const int dec64table[] = {8, 8, 8, 7, 8, 9,10,11};   /* subtracted */
-    const BYTE* const ostart = op;
-    BYTE* const oLitEnd = op + sequence.litLength;
-    const size_t litLength = sequence.litLength;
-    BYTE* const endMatch = op + litLength + sequence.matchLength;    /* risk : address space overflow (32-bits) */
-    const BYTE* const litEnd = *litPtr + litLength;
-
-    /* checks */
-    size_t const seqLength = sequence.litLength + sequence.matchLength;
-
-    if (seqLength > (size_t)(oend - op)) return ERROR(dstSize_tooSmall);
-    if (sequence.litLength > (size_t)(litLimit - *litPtr)) return ERROR(corruption_detected);
-    /* Now we know there are no overflow in literal nor match lengths, can use pointer checks */
-    if (sequence.offset > (U32)(oLitEnd - base)) return ERROR(corruption_detected);
-
-    if (endMatch > oend) return ERROR(dstSize_tooSmall);   /* overwrite beyond dst buffer */
-    if (litEnd > litLimit) return ERROR(corruption_detected);   /* overRead beyond lit buffer */
-    if (sequence.matchLength > (size_t)(*litPtr-op)) return ERROR(dstSize_tooSmall);  /* overwrite literal segment */
-
-    /* copy Literals */
-    ZSTD_memmove(op, *litPtr, sequence.litLength);   /* note : v0.1 seems to allow scenarios where output or input are close to end of buffer */
-
-    op += litLength;
-    *litPtr = litEnd;   /* update for next sequence */
-
-    /* check : last match must be at a minimum distance of 8 from end of dest buffer */
-    if (oend-op < 8) return ERROR(dstSize_tooSmall);
-
-    /* copy Match */
-    {
-        const U32 overlapRisk = (((size_t)(litEnd - endMatch)) < 12);
-        const BYTE* match = op - sequence.offset;            /* possible underflow at op - offset ? */
-        size_t qutt = 12;
-        U64 saved[2];
-
-        /* check */
-        if (match < base) return ERROR(corruption_detected);
-        if (sequence.offset > (size_t)base) return ERROR(corruption_detected);
-
-        /* save beginning of literal sequence, in case of write overlap */
-        if (overlapRisk)
-        {
-            if ((endMatch + qutt) > oend) qutt = oend-endMatch;
-            memcpy(saved, endMatch, qutt);
-        }
-
-        if (sequence.offset < 8)
-        {
-            const int dec64 = dec64table[sequence.offset];
-            op[0] = match[0];
-            op[1] = match[1];
-            op[2] = match[2];
-            op[3] = match[3];
-            match += dec32table[sequence.offset];
-            ZSTD_copy4(op+4, match);
-            match -= dec64;
-        } else { ZSTD_copy8(op, match); }
-        op += 8; match += 8;
-
-        if (endMatch > oend-(16-MINMATCH))
-        {
-            if (op < oend-8)
-            {
-                ZSTD_wildcopy(op, match, (oend-8) - op);
-                match += (oend-8) - op;
-                op = oend-8;
-            }
-            while (op<endMatch) *op++ = *match++;
-        }
-        else
-            ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength-8);   /* works even if matchLength < 8 */
-
-        /* restore, in case of overlap */
-        if (overlapRisk) memcpy(endMatch, saved, qutt);
-    }
-
-    return endMatch-ostart;
-}
-
-typedef struct ZSTDv01_Dctx_s
-{
-    U32 LLTable[FSE_DTABLE_SIZE_U32(LLFSELog)];
-    U32 OffTable[FSE_DTABLE_SIZE_U32(OffFSELog)];
-    U32 MLTable[FSE_DTABLE_SIZE_U32(MLFSELog)];
-    void* previousDstEnd;
-    void* base;
-    size_t expected;
-    blockType_t bType;
-    U32 phase;
-} dctx_t;
-
-
-static size_t ZSTD_decompressSequences(
-                               void* ctx,
-                               void* dst, size_t maxDstSize,
-                         const void* seqStart, size_t seqSize,
-                         const BYTE* litStart, size_t litSize)
-{
-    dctx_t* dctx = (dctx_t*)ctx;
-    const BYTE* ip = (const BYTE*)seqStart;
-    const BYTE* const iend = ip + seqSize;
-    BYTE* const ostart = (BYTE* const)dst;
-    BYTE* op = ostart;
-    BYTE* const oend = ostart + maxDstSize;
-    size_t errorCode, dumpsLength;
-    const BYTE* litPtr = litStart;
-    const BYTE* const litEnd = litStart + litSize;
-    int nbSeq;
-    const BYTE* dumps;
-    U32* DTableLL = dctx->LLTable;
-    U32* DTableML = dctx->MLTable;
-    U32* DTableOffb = dctx->OffTable;
-    BYTE* const base = (BYTE*) (dctx->base);
-
-    /* Build Decoding Tables */
-    errorCode = ZSTDv01_decodeSeqHeaders(&nbSeq, &dumps, &dumpsLength,
-                                      DTableLL, DTableML, DTableOffb,
-                                      ip, iend-ip);
-    if (ZSTDv01_isError(errorCode)) return errorCode;
-    ip += errorCode;
-
-    /* Regen sequences */
-    {
-        seq_t sequence;
-        seqState_t seqState;
-
-        memset(&sequence, 0, sizeof(sequence));
-        seqState.dumps = dumps;
-        seqState.dumpsEnd = dumps + dumpsLength;
-        seqState.prevOffset = 1;
-        errorCode = FSE_initDStream(&(seqState.DStream), ip, iend-ip);
-        if (FSE_isError(errorCode)) return ERROR(corruption_detected);
-        FSE_initDState(&(seqState.stateLL), &(seqState.DStream), DTableLL);
-        FSE_initDState(&(seqState.stateOffb), &(seqState.DStream), DTableOffb);
-        FSE_initDState(&(seqState.stateML), &(seqState.DStream), DTableML);
-
-        for ( ; (FSE_reloadDStream(&(seqState.DStream)) <= FSE_DStream_completed) && (nbSeq>0) ; )
-        {
-            size_t oneSeqSize;
-            nbSeq--;
-            ZSTD_decodeSequence(&sequence, &seqState);
-            oneSeqSize = ZSTD_execSequence(op, sequence, &litPtr, litEnd, base, oend);
-            if (ZSTDv01_isError(oneSeqSize)) return oneSeqSize;
-            op += oneSeqSize;
-        }
-
-        /* check if reached exact end */
-        if ( !FSE_endOfDStream(&(seqState.DStream)) ) return ERROR(corruption_detected);   /* requested too much : data is corrupted */
-        if (nbSeq<0) return ERROR(corruption_detected);   /* requested too many sequences : data is corrupted */
-
-        /* last literal segment */
-        {
-            size_t lastLLSize = litEnd - litPtr;
-            if (op+lastLLSize > oend) return ERROR(dstSize_tooSmall);
-            if (lastLLSize > 0) {
-                if (op != litPtr) memmove(op, litPtr, lastLLSize);
-                op += lastLLSize;
-            }
-        }
-    }
-
-    return op-ostart;
-}
-
-
-static size_t ZSTD_decompressBlock(
-                            void* ctx,
-                            void* dst, size_t maxDstSize,
-                      const void* src, size_t srcSize)
-{
-    /* blockType == blockCompressed, srcSize is trusted */
-    const BYTE* ip = (const BYTE*)src;
-    const BYTE* litPtr = NULL;
-    size_t litSize = 0;
-    size_t errorCode;
-
-    /* Decode literals sub-block */
-    errorCode = ZSTDv01_decodeLiteralsBlock(ctx, dst, maxDstSize, &litPtr, &litSize, src, srcSize);
-    if (ZSTDv01_isError(errorCode)) return errorCode;
-    ip += errorCode;
-    srcSize -= errorCode;
-
-    return ZSTD_decompressSequences(ctx, dst, maxDstSize, ip, srcSize, litPtr, litSize);
-}
-
-
-size_t ZSTDv01_decompressDCtx(void* ctx, void* dst, size_t maxDstSize, const void* src, size_t srcSize)
-{
-    const BYTE* ip = (const BYTE*)src;
-    const BYTE* iend = ip + srcSize;
-    BYTE* const ostart = (BYTE* const)dst;
-    BYTE* op = ostart;
-    BYTE* const oend = ostart + maxDstSize;
-    size_t remainingSize = srcSize;
-    U32 magicNumber;
-    size_t errorCode=0;
-    blockProperties_t blockProperties;
-
-    /* Frame Header */
-    if (srcSize < ZSTD_frameHeaderSize+ZSTD_blockHeaderSize) return ERROR(srcSize_wrong);
-    magicNumber = ZSTD_readBE32(src);
-    if (magicNumber != ZSTD_magicNumber) return ERROR(prefix_unknown);
-    ip += ZSTD_frameHeaderSize; remainingSize -= ZSTD_frameHeaderSize;
-
-    /* Loop on each block */
-    while (1)
-    {
-        size_t blockSize = ZSTDv01_getcBlockSize(ip, iend-ip, &blockProperties);
-        if (ZSTDv01_isError(blockSize)) return blockSize;
-
-        ip += ZSTD_blockHeaderSize;
-        remainingSize -= ZSTD_blockHeaderSize;
-        if (blockSize > remainingSize) return ERROR(srcSize_wrong);
-
-        switch(blockProperties.blockType)
-        {
-        case bt_compressed:
-            errorCode = ZSTD_decompressBlock(ctx, op, oend-op, ip, blockSize);
-            break;
-        case bt_raw :
-            errorCode = ZSTD_copyUncompressedBlock(op, oend-op, ip, blockSize);
-            break;
-        case bt_rle :
-            return ERROR(GENERIC);   /* not yet supported */
-            break;
-        case bt_end :
-            /* end of frame */
-            if (remainingSize) return ERROR(srcSize_wrong);
-            break;
-        default:
-            return ERROR(GENERIC);
-        }
-        if (blockSize == 0) break;   /* bt_end */
-
-        if (ZSTDv01_isError(errorCode)) return errorCode;
-        op += errorCode;
-        ip += blockSize;
-        remainingSize -= blockSize;
-    }
-
-    return op-ostart;
-}
-
-size_t ZSTDv01_decompress(void* dst, size_t maxDstSize, const void* src, size_t srcSize)
-{
-    dctx_t ctx;
-    ctx.base = dst;
-    return ZSTDv01_decompressDCtx(&ctx, dst, maxDstSize, src, srcSize);
-}
-
-/* ZSTD_errorFrameSizeInfoLegacy() :
-   assumes `cSize` and `dBound` are _not_ NULL */
-static void ZSTD_errorFrameSizeInfoLegacy(size_t* cSize, unsigned long long* dBound, size_t ret)
-{
-    *cSize = ret;
-    *dBound = ZSTD_CONTENTSIZE_ERROR;
-}
-
-void ZSTDv01_findFrameSizeInfoLegacy(const void *src, size_t srcSize, size_t* cSize, unsigned long long* dBound)
-{
-    const BYTE* ip = (const BYTE*)src;
-    size_t remainingSize = srcSize;
-    size_t nbBlocks = 0;
-    U32 magicNumber;
-    blockProperties_t blockProperties;
-
-    /* Frame Header */
-    if (srcSize < ZSTD_frameHeaderSize+ZSTD_blockHeaderSize) {
-        ZSTD_errorFrameSizeInfoLegacy(cSize, dBound, ERROR(srcSize_wrong));
-        return;
-    }
-    magicNumber = ZSTD_readBE32(src);
-    if (magicNumber != ZSTD_magicNumber) {
-        ZSTD_errorFrameSizeInfoLegacy(cSize, dBound, ERROR(prefix_unknown));
-        return;
-    }
-    ip += ZSTD_frameHeaderSize; remainingSize -= ZSTD_frameHeaderSize;
-
-    /* Loop on each block */
-    while (1)
-    {
-        size_t blockSize = ZSTDv01_getcBlockSize(ip, remainingSize, &blockProperties);
-        if (ZSTDv01_isError(blockSize)) {
-            ZSTD_errorFrameSizeInfoLegacy(cSize, dBound, blockSize);
-            return;
-        }
-
-        ip += ZSTD_blockHeaderSize;
-        remainingSize -= ZSTD_blockHeaderSize;
-        if (blockSize > remainingSize) {
-            ZSTD_errorFrameSizeInfoLegacy(cSize, dBound, ERROR(srcSize_wrong));
-            return;
-        }
-
-        if (blockSize == 0) break;   /* bt_end */
-
-        ip += blockSize;
-        remainingSize -= blockSize;
-        nbBlocks++;
-    }
-
-    *cSize = ip - (const BYTE*)src;
-    *dBound = nbBlocks * BLOCKSIZE;
-}
-
-/*******************************
-*  Streaming Decompression API
-*******************************/
-
-size_t ZSTDv01_resetDCtx(ZSTDv01_Dctx* dctx)
-{
-    dctx->expected = ZSTD_frameHeaderSize;
-    dctx->phase = 0;
-    dctx->previousDstEnd = NULL;
-    dctx->base = NULL;
-    return 0;
-}
-
-ZSTDv01_Dctx* ZSTDv01_createDCtx(void)
-{
-    ZSTDv01_Dctx* dctx = (ZSTDv01_Dctx*)malloc(sizeof(ZSTDv01_Dctx));
-    if (dctx==NULL) return NULL;
-    ZSTDv01_resetDCtx(dctx);
-    return dctx;
-}
-
-size_t ZSTDv01_freeDCtx(ZSTDv01_Dctx* dctx)
-{
-    free(dctx);
-    return 0;
-}
-
-size_t ZSTDv01_nextSrcSizeToDecompress(ZSTDv01_Dctx* dctx)
-{
-    return ((dctx_t*)dctx)->expected;
-}
-
-size_t ZSTDv01_decompressContinue(ZSTDv01_Dctx* dctx, void* dst, size_t maxDstSize, const void* src, size_t srcSize)
-{
-    dctx_t* ctx = (dctx_t*)dctx;
-
-    /* Sanity check */
-    if (srcSize != ctx->expected) return ERROR(srcSize_wrong);
-    if (dst != ctx->previousDstEnd)  /* not contiguous */
-        ctx->base = dst;
-
-    /* Decompress : frame header */
-    if (ctx->phase == 0)
-    {
-        /* Check frame magic header */
-        U32 magicNumber = ZSTD_readBE32(src);
-        if (magicNumber != ZSTD_magicNumber) return ERROR(prefix_unknown);
-        ctx->phase = 1;
-        ctx->expected = ZSTD_blockHeaderSize;
-        return 0;
-    }
-
-    /* Decompress : block header */
-    if (ctx->phase == 1)
-    {
-        blockProperties_t bp;
-        size_t blockSize = ZSTDv01_getcBlockSize(src, ZSTD_blockHeaderSize, &bp);
-        if (ZSTDv01_isError(blockSize)) return blockSize;
-        if (bp.blockType == bt_end)
-        {
-            ctx->expected = 0;
-            ctx->phase = 0;
-        }
-        else
-        {
-            ctx->expected = blockSize;
-            ctx->bType = bp.blockType;
-            ctx->phase = 2;
-        }
-
-        return 0;
-    }
-
-    /* Decompress : block content */
-    {
-        size_t rSize;
-        switch(ctx->bType)
-        {
-        case bt_compressed:
-            rSize = ZSTD_decompressBlock(ctx, dst, maxDstSize, src, srcSize);
-            break;
-        case bt_raw :
-            rSize = ZSTD_copyUncompressedBlock(dst, maxDstSize, src, srcSize);
-            break;
-        case bt_rle :
-            return ERROR(GENERIC);   /* not yet handled */
-            break;
-        case bt_end :   /* should never happen (filtered at phase 1) */
-            rSize = 0;
-            break;
-        default:
-            return ERROR(GENERIC);
-        }
-        ctx->phase = 1;
-        ctx->expected = ZSTD_blockHeaderSize;
-        if (ZSTDv01_isError(rSize)) return rSize;
-        ctx->previousDstEnd = (void*)( ((char*)dst) + rSize);
-        return rSize;
-    }
-
-}

programs/Makefile

@@ -32,7 +32,8 @@ RUST_CLI_MANIFEST := $(RUST_CLI_DIR)/Cargo.toml
 RUST_SOURCES := $(RUST_MANIFEST) $(RUST_DIR)/Cargo.lock \
                 $(shell find $(RUST_DIR)/src -type f -name '*.rs' -print)
 RUST_CLI_SOURCES := $(RUST_CLI_MANIFEST) $(RUST_CLI_DIR)/Cargo.lock \
-                    $(RUST_CLI_DIR)/src/lib.rs $(RUST_DIR)/src/zstd_cli.rs
+                    $(RUST_CLI_DIR)/src/lib.rs $(RUST_DIR)/src/zstd_cli.rs \
+                    $(RUST_DIR)/src/timefn.rs $(RUST_DIR)/src/benchfn.rs
 
 # Keep Rust's HUF implementation in lockstep with libzstd.mk's C selection.
 # Forced modes may arrive as libzstd.mk variables or as direct -D flags in
@@ -55,16 +56,33 @@ endif
 endif
 
 RUST_HUF_FEATURE :=
-RUST_BUILD_CONFIG := default
+RUST_HUF_MODE := default
 ifneq ($(RUST_HUF_FORCE_X1),0)
 RUST_HUF_FEATURE := huf-force-decompress-x1
-RUST_BUILD_CONFIG := huf-force-decompress-x1
+RUST_HUF_MODE := huf-force-decompress-x1
 endif
 ifneq ($(RUST_HUF_FORCE_X2),0)
 RUST_HUF_FEATURE := huf-force-decompress-x2
-RUST_BUILD_CONFIG := huf-force-decompress-x2
+RUST_HUF_MODE := huf-force-decompress-x2
 endif
 
+# The full-featured zstd program mirrors libzstd.mk's legacy file selection:
+# ZSTD_LEGACY_SUPPORT=N compiles v0.N .. v0.7, so the Rust archive enables the
+# matching per-version features.  The archive directory encodes the level so
+# builds for different legacy levels never share cached Rust outputs.  The
+# compress-only, decompress-only, and CLI archives further below are used
+# solely by ZSTD_LEGACY_SUPPORT=0 program variants and stay legacy-free.
+empty :=
+space := $(empty) $(empty)
+comma := ,
+RUST_LEGACY_FEATURES :=
+ifneq ($(ZSTD_LEGACY_SUPPORT), 0)
+ifeq ($(shell test $(ZSTD_LEGACY_SUPPORT) -lt 8; echo $$?), 0)
+RUST_LEGACY_FEATURES := $(addprefix legacy-v0,$(wordlist $(ZSTD_LEGACY_SUPPORT),7,1 2 3 4 5 6 7))
+endif
+endif
+RUST_BUILD_CONFIG := $(RUST_HUF_MODE)-legacy$(ZSTD_LEGACY_SUPPORT)
+
 RUST_TARGET_DIR := $(RUST_DIR)/target/$(RUST_BUILD_CONFIG)
 RUST_STATICLIB := $(RUST_TARGET_DIR)/release/libzstd_rs.a
 RUST_TARGET_32 ?= i686-unknown-linux-gnu
@@ -75,6 +93,9 @@ RUST_CARGO_FLAGS += --features compression,decompression,dict-builder
 ifneq ($(RUST_HUF_FEATURE),)
 RUST_CARGO_FLAGS += --features $(RUST_HUF_FEATURE)
 endif
+ifneq ($(RUST_LEGACY_FEATURES),)
+RUST_CARGO_FLAGS += --features $(subst $(space),$(comma),$(strip $(RUST_LEGACY_FEATURES)))
+endif
 
 $(RUST_STATICLIB): $(RUST_SOURCES)
 	$(CARGO) build $(RUST_CARGO_FLAGS)
@@ -82,13 +103,13 @@ $(RUST_STATICLIB): $(RUST_SOURCES)
 $(RUST_STATICLIB_32): $(RUST_SOURCES)
 	$(CARGO) build $(RUST_CARGO_FLAGS) --target $(RUST_TARGET_32)
 
-RUST_CLI_BUILD_CONFIG := cli-c1-d1-$(RUST_BUILD_CONFIG)
+RUST_CLI_BUILD_CONFIG := cli-c1-d1-$(RUST_HUF_MODE)
 RUST_CLI_TARGET_DIR := $(RUST_DIR)/target/$(RUST_CLI_BUILD_CONFIG)
 RUST_CLI_STATICLIB := $(RUST_CLI_TARGET_DIR)/release/libzstd_cli_rs.a
 RUST_CLI_STATICLIB_32 := $(RUST_CLI_TARGET_DIR)/$(RUST_TARGET_32)/release/libzstd_cli_rs.a
 RUST_CLI_CARGO_FLAGS := --manifest-path $(RUST_CLI_MANIFEST) --release \
                         --target-dir $(RUST_CLI_TARGET_DIR) \
-                        --no-default-features --features compression,decompression
+                        --no-default-features --features cli,compression,decompression
 
 $(RUST_CLI_STATICLIB): $(RUST_CLI_SOURCES)
 	$(CARGO) build $(RUST_CLI_CARGO_FLAGS)
@@ -96,7 +117,7 @@ $(RUST_CLI_STATICLIB): $(RUST_CLI_SOURCES)
 $(RUST_CLI_STATICLIB_32): $(RUST_CLI_SOURCES)
 	$(CARGO) build $(RUST_CLI_CARGO_FLAGS) --target $(RUST_TARGET_32)
 
-RUST_DECOMPRESS_BUILD_CONFIG := lib-c0-d1-b0-$(RUST_BUILD_CONFIG)
+RUST_DECOMPRESS_BUILD_CONFIG := lib-c0-d1-b0-$(RUST_HUF_MODE)
 RUST_DECOMPRESS_TARGET_DIR := $(RUST_DIR)/target/$(RUST_DECOMPRESS_BUILD_CONFIG)
 RUST_DECOMPRESS_STATICLIB := $(RUST_DECOMPRESS_TARGET_DIR)/release/libzstd_rs.a
 RUST_DECOMPRESS_CARGO_FLAGS := --manifest-path $(RUST_MANIFEST) --release \
@@ -109,17 +130,17 @@ endif
 $(RUST_DECOMPRESS_STATICLIB): $(RUST_SOURCES)
 	$(CARGO) build $(RUST_DECOMPRESS_CARGO_FLAGS)
 
-RUST_DECOMPRESS_CLI_BUILD_CONFIG := cli-c0-d1-$(RUST_BUILD_CONFIG)
+RUST_DECOMPRESS_CLI_BUILD_CONFIG := cli-c0-d1-$(RUST_HUF_MODE)
 RUST_DECOMPRESS_CLI_TARGET_DIR := $(RUST_DIR)/target/$(RUST_DECOMPRESS_CLI_BUILD_CONFIG)
 RUST_DECOMPRESS_CLI_STATICLIB := $(RUST_DECOMPRESS_CLI_TARGET_DIR)/release/libzstd_cli_rs.a
 RUST_DECOMPRESS_CLI_CARGO_FLAGS := --manifest-path $(RUST_CLI_MANIFEST) --release \
                                     --target-dir $(RUST_DECOMPRESS_CLI_TARGET_DIR) \
-                                    --no-default-features --features decompression
+                                    --no-default-features --features cli,decompression
 
 $(RUST_DECOMPRESS_CLI_STATICLIB): $(RUST_CLI_SOURCES)
 	$(CARGO) build $(RUST_DECOMPRESS_CLI_CARGO_FLAGS)
 
-RUST_COMPRESS_BUILD_CONFIG := lib-c1-d0-b0-$(RUST_BUILD_CONFIG)
+RUST_COMPRESS_BUILD_CONFIG := lib-c1-d0-b0-$(RUST_HUF_MODE)
 RUST_COMPRESS_TARGET_DIR := $(RUST_DIR)/target/$(RUST_COMPRESS_BUILD_CONFIG)
 RUST_COMPRESS_STATICLIB := $(RUST_COMPRESS_TARGET_DIR)/release/libzstd_rs.a
 RUST_COMPRESS_CARGO_FLAGS := --manifest-path $(RUST_MANIFEST) --release \
@@ -129,7 +150,7 @@ RUST_COMPRESS_CARGO_FLAGS := --manifest-path $(RUST_MANIFEST) --release \
 $(RUST_COMPRESS_STATICLIB): $(RUST_SOURCES)
 	$(CARGO) build $(RUST_COMPRESS_CARGO_FLAGS)
 
-RUST_DICTBUILDER_BUILD_CONFIG := lib-c1-d0-b1-$(RUST_BUILD_CONFIG)
+RUST_DICTBUILDER_BUILD_CONFIG := lib-c1-d0-b1-$(RUST_HUF_MODE)
 RUST_DICTBUILDER_TARGET_DIR := $(RUST_DIR)/target/$(RUST_DICTBUILDER_BUILD_CONFIG)
 RUST_DICTBUILDER_STATICLIB := $(RUST_DICTBUILDER_TARGET_DIR)/release/libzstd_rs.a
 RUST_DICTBUILDER_CARGO_FLAGS := --manifest-path $(RUST_MANIFEST) --release \
@@ -140,12 +161,12 @@ RUST_DICTBUILDER_CARGO_FLAGS := --manifest-path $(RUST_MANIFEST) --release \
 $(RUST_DICTBUILDER_STATICLIB): $(RUST_SOURCES)
 	$(CARGO) build $(RUST_DICTBUILDER_CARGO_FLAGS)
 
-RUST_COMPRESS_CLI_BUILD_CONFIG := cli-c1-d0-$(RUST_BUILD_CONFIG)
+RUST_COMPRESS_CLI_BUILD_CONFIG := cli-c1-d0-$(RUST_HUF_MODE)
 RUST_COMPRESS_CLI_TARGET_DIR := $(RUST_DIR)/target/$(RUST_COMPRESS_CLI_BUILD_CONFIG)
 RUST_COMPRESS_CLI_STATICLIB := $(RUST_COMPRESS_CLI_TARGET_DIR)/release/libzstd_cli_rs.a
 RUST_COMPRESS_CLI_CARGO_FLAGS := --manifest-path $(RUST_CLI_MANIFEST) --release \
                                   --target-dir $(RUST_COMPRESS_CLI_TARGET_DIR) \
-                                  --no-default-features --features compression
+                                  --no-default-features --features cli,compression
 
 $(RUST_COMPRESS_CLI_STATICLIB): $(RUST_CLI_SOURCES)
 	$(CARGO) build $(RUST_COMPRESS_CLI_CARGO_FLAGS)

programs/benchfn.c

@@ -8,249 +8,23 @@
  * You may select, at your option, one of the above-listed licenses.
  */
 
+/* The implementation lives in rust/src/benchfn.rs, built into the Rust CLI
+ * static archive. This translation unit stays in the original source lists so
+ * build configuration keeps working while the implementation is in Rust. */
 
-
+#include <stddef.h>   /* size_t, offsetof */
-/* *************************************
-*  Includes
-***************************************/
-#include <stdlib.h>      /* malloc, free */
-#include <string.h>      /* memset */
-#include <assert.h>      /* assert */
-
-#include "timefn.h"        /* UTIL_time_t, UTIL_getTime */
 #include "benchfn.h"
 
-
+/* BMK_runTime_t and BMK_runOutcome_t are returned by value across the C/Rust
-/* *************************************
+ * boundary, and BMK_benchParams_t is passed by value. The Rust #[repr(C)]
-*  Constants
+ * definitions mirror the offsets pinned here. */
-***************************************/
+typedef char BMK_staticAssert_runTimeSumOffset[
-#define TIMELOOP_MICROSEC     SEC_TO_MICRO      /* 1 second */
+    (offsetof(BMK_runTime_t, sumOfReturn) == sizeof(double)) ? 1 : -1];
-#define TIMELOOP_NANOSEC      (1*1000000000ULL) /* 1 second */
+typedef char BMK_staticAssert_outcomeResultOffset[
-
+    (offsetof(BMK_runOutcome_t, error_result_never_ever_use_directly)
-#define KB *(1 <<10)
+     == sizeof(BMK_runTime_t)) ? 1 : -1];
-#define MB *(1 <<20)
+typedef char BMK_staticAssert_outcomeTagOffset[
-#define GB *(1U<<30)
+    (offsetof(BMK_runOutcome_t, error_tag_never_ever_use_directly)
-
+     == sizeof(BMK_runTime_t) + sizeof(size_t)) ? 1 : -1];
-
+typedef char BMK_staticAssert_shellAlignment[
-/* *************************************
+    (sizeof(BMK_timedFnState_shell) == BMK_TIMEDFNSTATE_SIZE) ? 1 : -1];
-*  Debug errors
-***************************************/
-#if defined(DEBUG) && (DEBUG >= 1)
-#  include <stdio.h>       /* fprintf */
-#  define DISPLAY(...)       fprintf(stderr, __VA_ARGS__)
-#  define DEBUGOUTPUT(...) { if (DEBUG) DISPLAY(__VA_ARGS__); }
-#else
-#  define DEBUGOUTPUT(...)
-#endif
-
-
-/* error without displaying */
-#define RETURN_QUIET_ERROR(retValue, ...) {           \
-    DEBUGOUTPUT("%s: %i: \n", __FILE__, __LINE__);    \
-    DEBUGOUTPUT("Error : ");                          \
-    DEBUGOUTPUT(__VA_ARGS__);                         \
-    DEBUGOUTPUT(" \n");                               \
-    return retValue;                                  \
-}
-
-/* Abort execution if a condition is not met */
-#define CONTROL(c) { if (!(c)) { DEBUGOUTPUT("error: %s \n", #c); abort(); } }
-
-
-/* *************************************
-*  Benchmarking an arbitrary function
-***************************************/
-
-int BMK_isSuccessful_runOutcome(BMK_runOutcome_t outcome)
-{
-    return outcome.error_tag_never_ever_use_directly == 0;
-}
-
-/* warning : this function will stop program execution if outcome is invalid !
- *           check outcome validity first, using BMK_isValid_runResult() */
-BMK_runTime_t BMK_extract_runTime(BMK_runOutcome_t outcome)
-{
-    CONTROL(outcome.error_tag_never_ever_use_directly == 0);
-    return outcome.internal_never_ever_use_directly;
-}
-
-size_t BMK_extract_errorResult(BMK_runOutcome_t outcome)
-{
-    CONTROL(outcome.error_tag_never_ever_use_directly != 0);
-    return outcome.error_result_never_ever_use_directly;
-}
-
-static BMK_runOutcome_t BMK_runOutcome_error(size_t errorResult)
-{
-    BMK_runOutcome_t b;
-    memset(&b, 0, sizeof(b));
-    b.error_tag_never_ever_use_directly = 1;
-    b.error_result_never_ever_use_directly = errorResult;
-    return b;
-}
-
-static BMK_runOutcome_t BMK_setValid_runTime(BMK_runTime_t runTime)
-{
-    BMK_runOutcome_t outcome;
-    outcome.error_tag_never_ever_use_directly = 0;
-    outcome.internal_never_ever_use_directly = runTime;
-    return outcome;
-}
-
-
-/* initFn will be measured once, benchFn will be measured `nbLoops` times */
-/* initFn is optional, provide NULL if none */
-/* benchFn must return a size_t value that errorFn can interpret */
-/* takes # of blocks and list of size & stuff for each. */
-/* can report result of benchFn for each block into blockResult. */
-/* blockResult is optional, provide NULL if this information is not required */
-/* note : time per loop can be reported as zero if run time < timer resolution */
-BMK_runOutcome_t BMK_benchFunction(BMK_benchParams_t p,
-                                   unsigned nbLoops)
-{
-    nbLoops += !nbLoops;   /* minimum nbLoops is 1 */
-
-    /* init */
-    {   size_t i;
-        for(i = 0; i < p.blockCount; i++) {
-            memset(p.dstBuffers[i], 0xE5, p.dstCapacities[i]);  /* warm up and erase result buffer */
-    }   }
-
-    /* benchmark */
-    {   size_t dstSize = 0;
-        UTIL_time_t const clockStart = UTIL_getTime();
-        unsigned loopNb, blockNb;
-        if (p.initFn != NULL) p.initFn(p.initPayload);
-        for (loopNb = 0; loopNb < nbLoops; loopNb++) {
-            for (blockNb = 0; blockNb < p.blockCount; blockNb++) {
-                size_t const res = p.benchFn(p.srcBuffers[blockNb], p.srcSizes[blockNb],
-                                   p.dstBuffers[blockNb], p.dstCapacities[blockNb],
-                                   p.benchPayload);
-                if (loopNb == 0) {
-                    if (p.blockResults != NULL) p.blockResults[blockNb] = res;
-                    if ((p.errorFn != NULL) && (p.errorFn(res))) {
-                        RETURN_QUIET_ERROR(BMK_runOutcome_error(res),
-                            "Function benchmark failed on block %u (of size %u) with error %i",
-                            blockNb, (unsigned)p.srcSizes[blockNb], (int)res);
-                    }
-                    dstSize += res;
-            }   }
-        }  /* for (loopNb = 0; loopNb < nbLoops; loopNb++) */
-
-        {   PTime const totalTime = UTIL_clockSpanNano(clockStart);
-            BMK_runTime_t rt;
-            rt.nanoSecPerRun = (double)totalTime / nbLoops;
-            rt.sumOfReturn = dstSize;
-            return BMK_setValid_runTime(rt);
-    }   }
-}
-
-
-/* ====  Benchmarking any function, providing intermediate results  ==== */
-
-struct BMK_timedFnState_s {
-    PTime timeSpent_ns;
-    PTime timeBudget_ns;
-    PTime runBudget_ns;
-    BMK_runTime_t fastestRun;
-    unsigned nbLoops;
-    UTIL_time_t coolTime;
-};  /* typedef'd to BMK_timedFnState_t within bench.h */
-
-BMK_timedFnState_t* BMK_createTimedFnState(unsigned total_ms, unsigned run_ms)
-{
-    BMK_timedFnState_t* const r = (BMK_timedFnState_t*)malloc(sizeof(*r));
-    if (r == NULL) return NULL;   /* malloc() error */
-    BMK_resetTimedFnState(r, total_ms, run_ms);
-    return r;
-}
-
-void BMK_freeTimedFnState(BMK_timedFnState_t* state) { free(state); }
-
-BMK_timedFnState_t*
-BMK_initStatic_timedFnState(void* buffer, size_t size, unsigned total_ms, unsigned run_ms)
-{
-    typedef char check_size[ 2 * (sizeof(BMK_timedFnState_shell) >= sizeof(struct BMK_timedFnState_s)) - 1];  /* static assert : a compilation failure indicates that BMK_timedFnState_shell is not large enough */
-    typedef struct { check_size c; BMK_timedFnState_t tfs; } tfs_align;  /* force tfs to be aligned at its next best position */
-    size_t const tfs_alignment = offsetof(tfs_align, tfs); /* provides the minimal alignment restriction for BMK_timedFnState_t */
-    BMK_timedFnState_t* const r = (BMK_timedFnState_t*)buffer;
-    if (buffer == NULL) return NULL;
-    if (size < sizeof(struct BMK_timedFnState_s)) return NULL;
-    if ((size_t)buffer % tfs_alignment) return NULL;  /* buffer must be properly aligned */
-    BMK_resetTimedFnState(r, total_ms, run_ms);
-    return r;
-}
-
-void BMK_resetTimedFnState(BMK_timedFnState_t* timedFnState, unsigned total_ms, unsigned run_ms)
-{
-    if (!total_ms) total_ms = 1 ;
-    if (!run_ms) run_ms = 1;
-    if (run_ms > total_ms) run_ms = total_ms;
-    timedFnState->timeSpent_ns = 0;
-    timedFnState->timeBudget_ns = (PTime)total_ms * TIMELOOP_NANOSEC / 1000;
-    timedFnState->runBudget_ns = (PTime)run_ms * TIMELOOP_NANOSEC / 1000;
-    timedFnState->fastestRun.nanoSecPerRun = (double)TIMELOOP_NANOSEC * 2000000000;  /* hopefully large enough : must be larger than any potential measurement */
-    timedFnState->fastestRun.sumOfReturn = (size_t)(-1LL);
-    timedFnState->nbLoops = 1;
-    timedFnState->coolTime = UTIL_getTime();
-}
-
-/* Tells if nb of seconds set in timedFnState for all runs is spent.
- * note : this function will return 1 if BMK_benchFunctionTimed() has actually errored. */
-int BMK_isCompleted_TimedFn(const BMK_timedFnState_t* timedFnState)
-{
-    return (timedFnState->timeSpent_ns >= timedFnState->timeBudget_ns);
-}
-
-
-#undef MIN
-#define MIN(a,b)   ( (a) < (b) ? (a) : (b) )
-
-#define MINUSABLETIME  (TIMELOOP_NANOSEC / 2)  /* 0.5 seconds */
-
-BMK_runOutcome_t BMK_benchTimedFn(BMK_timedFnState_t* cont,
-                                  BMK_benchParams_t p)
-{
-    PTime const runBudget_ns = cont->runBudget_ns;
-    PTime const runTimeMin_ns = runBudget_ns / 2;
-    int completed = 0;
-    BMK_runTime_t bestRunTime = cont->fastestRun;
-
-    while (!completed) {
-        BMK_runOutcome_t const runResult = BMK_benchFunction(p, cont->nbLoops);
-
-        if(!BMK_isSuccessful_runOutcome(runResult)) { /* error : move out */
-            return runResult;
-        }
-
-        {   BMK_runTime_t const newRunTime = BMK_extract_runTime(runResult);
-            double const loopDuration_ns = newRunTime.nanoSecPerRun * cont->nbLoops;
-
-            cont->timeSpent_ns += (unsigned long long)loopDuration_ns;
-
-            /* estimate nbLoops for next run to last approximately 1 second */
-            if (loopDuration_ns > ((double)runBudget_ns / 50)) {
-                double const fastestRun_ns = MIN(bestRunTime.nanoSecPerRun, newRunTime.nanoSecPerRun);
-                cont->nbLoops = (unsigned)((double)runBudget_ns / fastestRun_ns) + 1;
-            } else {
-                /* previous run was too short : blindly increase workload by x multiplier */
-                const unsigned multiplier = 10;
-                assert(cont->nbLoops < ((unsigned)-1) / multiplier);  /* avoid overflow */
-                cont->nbLoops *= multiplier;
-            }
-
-            if(loopDuration_ns < (double)runTimeMin_ns) {
-                /* don't report results for which benchmark run time was too small : increased risks of rounding errors */
-                assert(completed == 0);
-                continue;
-            } else {
-                if(newRunTime.nanoSecPerRun < bestRunTime.nanoSecPerRun) {
-                    bestRunTime = newRunTime;
-                }
-                completed = 1;
-            }
-        }
-    }   /* while (!completed) */
-
-    return BMK_setValid_runTime(bestRunTime);
-}

programs/timefn.c

@@ -8,161 +8,14 @@
  * You may select, at your option, one of the above-listed licenses.
  */
 
-
+/* The implementation lives in rust/src/timefn.rs, built into the Rust CLI
-/* ===  Dependencies  === */
+ * static archive. This translation unit stays in the original source lists so
+ * build configuration keeps working while the implementation is in Rust. */
 
 #include "timefn.h"
-#include "platform.h" /* set _POSIX_C_SOURCE */
-#include <time.h>     /* CLOCK_MONOTONIC, TIME_UTC */
 
-/*-****************************************
+/* The Rust port mirrors this exact ABI: UTIL_time_t is returned by value and
-*  Time functions
+ * must remain a plain 64-bit nanosecond counter. */
-******************************************/
+typedef char UTIL_staticAssert_ptimeIs64Bit[(sizeof(PTime) == 8) ? 1 : -1];
-
+typedef char UTIL_staticAssert_timeIsPlainCounter[
-#if defined(_WIN32)   /* Windows */
+    (sizeof(UTIL_time_t) == sizeof(PTime)) ? 1 : -1];
-
-#include <windows.h>  /* LARGE_INTEGER */
-#include <stdlib.h>   /* abort */
-#include <stdio.h>    /* perror */
-
-UTIL_time_t UTIL_getTime(void)
-{
-    static LARGE_INTEGER ticksPerSecond;
-    static int init = 0;
-    if (!init) {
-        if (!QueryPerformanceFrequency(&ticksPerSecond)) {
-            perror("timefn::QueryPerformanceFrequency");
-            abort();
-        }
-        init = 1;
-    }
-    {   UTIL_time_t r;
-        LARGE_INTEGER x;
-        QueryPerformanceCounter(&x);
-        r.t = (PTime)(x.QuadPart * 1000000000ULL / ticksPerSecond.QuadPart);
-        return r;
-    }
-}
-
-
-#elif defined(__APPLE__) && defined(__MACH__)
-
-#include <mach/mach_time.h> /* mach_timebase_info_data_t, mach_timebase_info, mach_absolute_time */
-
-UTIL_time_t UTIL_getTime(void)
-{
-    static mach_timebase_info_data_t rate;
-    static int init = 0;
-    if (!init) {
-        mach_timebase_info(&rate);
-        init = 1;
-    }
-    {   UTIL_time_t r;
-        r.t = mach_absolute_time() * (PTime)rate.numer / (PTime)rate.denom;
-        return r;
-    }
-}
-
-/* POSIX.1-2001 (optional) */
-#elif defined(CLOCK_MONOTONIC)
-
-#include <stdlib.h>   /* abort */
-#include <stdio.h>    /* perror */
-
-UTIL_time_t UTIL_getTime(void)
-{
-    /* time must be initialized, othersize it may fail msan test.
-     * No good reason, likely a limitation of timespec_get() for some target */
-    struct timespec time = { 0, 0 };
-    if (clock_gettime(CLOCK_MONOTONIC, &time) != 0) {
-        perror("timefn::clock_gettime(CLOCK_MONOTONIC)");
-        abort();
-    }
-    {   UTIL_time_t r;
-        r.t = (PTime)time.tv_sec * 1000000000ULL + (PTime)time.tv_nsec;
-        return r;
-    }
-}
-
-
-/* C11 requires support of timespec_get().
- * However, FreeBSD 11 claims C11 compliance while lacking timespec_get().
- * Double confirm timespec_get() support by checking the definition of TIME_UTC.
- * However, some versions of Android manage to simultaneously define TIME_UTC
- * and lack timespec_get() support... */
-#elif (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L) /* C11 */) \
-    && defined(TIME_UTC) && !defined(__ANDROID__)
-
-#include <stdlib.h>   /* abort */
-#include <stdio.h>    /* perror */
-
-UTIL_time_t UTIL_getTime(void)
-{
-    /* time must be initialized, othersize it may fail msan test.
-     * No good reason, likely a limitation of timespec_get() for some target */
-    struct timespec time = { 0, 0 };
-    if (timespec_get(&time, TIME_UTC) != TIME_UTC) {
-        perror("timefn::timespec_get(TIME_UTC)");
-        abort();
-    }
-    {   UTIL_time_t r;
-        r.t = (PTime)time.tv_sec * 1000000000ULL + (PTime)time.tv_nsec;
-        return r;
-    }
-}
-
-
-#else   /* relies on standard C90 (note : clock_t produces wrong measurements for multi-threaded workloads) */
-
-UTIL_time_t UTIL_getTime(void)
-{
-    UTIL_time_t r;
-    r.t = (PTime)clock() * 1000000000ULL / CLOCKS_PER_SEC;
-    return r;
-}
-
-#define TIME_MT_MEASUREMENTS_NOT_SUPPORTED
-
-#endif
-
-/* ==== Common functions, valid for all time API ==== */
-
-PTime UTIL_getSpanTimeNano(UTIL_time_t clockStart, UTIL_time_t clockEnd)
-{
-    return clockEnd.t - clockStart.t;
-}
-
-PTime UTIL_getSpanTimeMicro(UTIL_time_t begin, UTIL_time_t end)
-{
-    return UTIL_getSpanTimeNano(begin, end) / 1000ULL;
-}
-
-PTime UTIL_clockSpanMicro(UTIL_time_t clockStart )
-{
-    UTIL_time_t const clockEnd = UTIL_getTime();
-    return UTIL_getSpanTimeMicro(clockStart, clockEnd);
-}
-
-PTime UTIL_clockSpanNano(UTIL_time_t clockStart )
-{
-    UTIL_time_t const clockEnd = UTIL_getTime();
-    return UTIL_getSpanTimeNano(clockStart, clockEnd);
-}
-
-void UTIL_waitForNextTick(void)
-{
-    UTIL_time_t const clockStart = UTIL_getTime();
-    UTIL_time_t clockEnd;
-    do {
-        clockEnd = UTIL_getTime();
-    } while (UTIL_getSpanTimeNano(clockStart, clockEnd) == 0);
-}
-
-int UTIL_support_MT_measurements(void)
-{
-# if defined(TIME_MT_MEASUREMENTS_NOT_SUPPORTED)
-    return 0;
-# else
-    return 1;
-# endif
-}

programs/zstdcli.c

@@ -10,16 +10,67 @@
 
 /* The CLI parser and control flow live in rust/src/zstd_cli.rs. Keep this
  * translation unit as the stable C entry point used by program launchers. */
+#include <stddef.h>       /* size_t */
+#define ZSTD_STATIC_LINKING_ONLY   /* ZSTD_compressionParameters */
 #include "../lib/zstd.h"
+#ifndef ZSTD_NOBENCH
+#  include "benchzstd.h"  /* BMK_benchFilesAdvanced, BMK_syntheticTest */
+#endif
 
 int ZSTD_rust_cli_main(int argCount, const char* const argv[]);
 const char* ZSTD_rust_cli_expected_version(void);
+int ZSTD_rust_cli_bench(const char* const* fileNames, unsigned nbFiles,
+                        const char* dictFileName,
+                        int startCLevel, int endCLevel,
+                        const ZSTD_compressionParameters* compressionParams,
+                        int displayLevel, unsigned nbSeconds,
+                        size_t blockSize, int nbWorkers);
 
 const char* ZSTD_rust_cli_expected_version(void)
 {
     return ZSTD_VERSION_STRING;
 }
 
+/* Benchmark bridge for the Rust CLI. Whether benchmarking exists is a C
+ * preprocessor property (ZSTD_NOBENCH), so the decision stays in this shim:
+ * the Rust frontend calls in unconditionally, and stripped program variants
+ * never reference benchmark symbols.
+ * @return the benchmark result code (>= 0), or -1 when unavailable. */
+int ZSTD_rust_cli_bench(const char* const* fileNames, unsigned nbFiles,
+                        const char* dictFileName,
+                        int startCLevel, int endCLevel,
+                        const ZSTD_compressionParameters* compressionParams,
+                        int displayLevel, unsigned nbSeconds,
+                        size_t blockSize, int nbWorkers)
+{
+#ifndef ZSTD_NOBENCH
+    BMK_advancedParams_t advancedParams = BMK_initAdvancedParams();
+    int startLevel = startCLevel;
+    int endLevel = endCLevel;
+    advancedParams.nbSeconds = nbSeconds;
+    advancedParams.blockSize = blockSize;
+    advancedParams.nbWorkers = nbWorkers;
+    if (startLevel > ZSTD_maxCLevel()) startLevel = ZSTD_maxCLevel();
+    if (endLevel > ZSTD_maxCLevel()) endLevel = ZSTD_maxCLevel();
+    if (endLevel < startLevel) endLevel = startLevel;
+    if (nbFiles == 0) {
+        /* No input file: benchmark a synthetic sample (lorem generator). */
+        return BMK_syntheticTest(-1.0, startLevel, endLevel,
+                                 compressionParams, displayLevel,
+                                 &advancedParams);
+    }
+    return BMK_benchFilesAdvanced(fileNames, nbFiles, dictFileName,
+                                  startLevel, endLevel,
+                                  compressionParams, displayLevel,
+                                  &advancedParams);
+#else
+    (void)fileNames; (void)nbFiles; (void)dictFileName;
+    (void)startCLevel; (void)endCLevel; (void)compressionParams;
+    (void)displayLevel; (void)nbSeconds; (void)blockSize; (void)nbWorkers;
+    return -1;
+#endif
+}
+
 int main(int argCount, const char* argv[])
 {
     return ZSTD_rust_cli_main(argCount, argv);

rust/Cargo.toml

@@ -13,6 +13,18 @@ decompression = []
 dict-builder = []
 huf-force-decompress-x1 = []
 huf-force-decompress-x2 = []
+# Legacy-format decoders (zstd v0.1 .. v0.7). Never default features: the
+# build systems map ZSTD_LEGACY_SUPPORT=N to the features for versions >= N,
+# exactly mirroring which lib/legacy/zstd_v0N.c files the C build compiles.
+# A feature whose version is not yet ported to Rust gates nothing; the
+# original C file still provides that decoder.
+legacy-v01 = []
+legacy-v02 = []
+legacy-v03 = []
+legacy-v04 = []
+legacy-v05 = []
+legacy-v06 = []
+legacy-v07 = []
 
 [dependencies]
 libc = "0.2"

rust/README.md

@@ -57,6 +57,10 @@ zstd ABI:
   - `pool` implements the bounded worker pool used by multithreaded compression.
 - Dictionary support
   - `zstd_ddict` owns, loads, copies, and references decode dictionaries.
+- Legacy decoding
+  - `legacy` hosts one frozen module per historical format; `legacy::zstd_v01`
+    ports the self-contained v0.1 decoder.  Versions v0.2 through v0.7 are
+    still C.
 - Block decompression
   - `zstd_decompress_block` decodes literal and sequence sections, maintains
     FSE/Huffman repeat state, and executes compressed-block sequences.
@@ -69,12 +73,58 @@ zstd ABI:
     so library builds do not acquire program-only dependencies.  The C
     `fileio` backend still owns file opening, safe replacement, sparse writes,
     metadata, and streaming I/O.
+  - `timefn` provides the monotonic nanosecond clock behind `UTIL_time_t`,
+    and `benchfn` owns the benchmark run/timing loop (`BMK_benchFunction`,
+    `BMK_benchTimedFn`) used by the CLI benchmark mode and by C test tools.
+    Both live in the `cli/` package, but C test binaries (fullbench, fuzzer,
+    zstreamtest, paramgrill, ...) link a helpers-only build of that archive,
+    produced without the package's `cli` feature, because the parser layer
+    requires the C `fileio` backend that tests do not compile.  Benchmark
+    orchestration and reporting (`benchzstd.c`) remain C, reached from the
+    Rust parser through the `ZSTD_NOBENCH`-gated bridge in `zstdcli.c`.
 
 The optimal block matcher, high-level frame compression, dictionary-building
-except suffix-array construction, legacy decoding callbacks, and the CLI
+except suffix-array construction, the legacy v0.2-v0.7 decoders, benchmark
-file-I/O backend are still C. They must move before the rewrite is complete.
+orchestration (`benchzstd`), and the CLI file-I/O backend are still C. They
-Keeping that boundary explicit prevents a passing hybrid build from being
+must move before the rewrite is complete. Keeping that boundary explicit
-mistaken for the final all-Rust result.
+prevents a passing hybrid build from being mistaken for the final all-Rust
+result.
+
+## Legacy decoding
+
+Each `lib/legacy/zstd_v0N.c` file is a frozen snapshot of the entropy coders
+and frame logic of one historical release. The Rust ports in `src/legacy/`
+keep that property: every version owns its own frozen FSE/Huff0 and frame
+logic, ported line by line, and must never reuse the modern entropy modules
+or share code with other legacy versions. Outputs and error codes must be
+byte-identical to the original C files. Their only shared dependency is the
+`errors` module, matching the C files' `error_private.h` include.
+
+Cargo features `legacy-v01` .. `legacy-v07` gate the per-version modules and
+are never default features. The build systems derive the feature list from
+the C configuration:
+
+- `lib/Makefile` and `programs/Makefile` map `ZSTD_LEGACY_SUPPORT=N` to the
+  features for versions >= N (0 disables legacy), matching the
+  `ZSTD_LEGACY_FILES` selection in `lib/libzstd.mk`.
+- `tests/Makefile` always enables all seven features because the test
+  objects compile every `lib/legacy/*.c` file regardless of dispatch level.
+- `build/meson` maps `legacy_level` like the makefiles; `build/cmake`
+  enables all seven whenever `ZSTD_LEGACY_SUPPORT` is on because it always
+  compiles all seven C files.
+
+Every build system also encodes the legacy selection in the Rust target
+directory name (for example `c1-d1-default-legacy5`), for the same reason the
+HUF mode is encoded there: a cached archive built for one configuration must
+never be linked into a build that expects another.
+
+A feature whose version has not been ported yet gates nothing; the original
+C file still provides that decoder, so mixed C/Rust legacy levels link
+cleanly. Porting a version means adding `src/legacy/zstd_v0N.rs`, registering
+it in `src/legacy/mod.rs` behind its feature, and reducing
+`lib/legacy/zstd_v0N.c` to a declaration-only shim. For v0.1 the streaming
+`ZSTDv01_Dctx` state lives entirely in Rust: C code only ever holds an opaque
+pointer, so the C-side struct definition is gone.
 
 ## Compatibility boundary
 
@@ -111,8 +161,9 @@ from `rust/cli` as well:
 ```sh
 cargo clippy --all-targets -- -D warnings
 cargo test --all-targets
-cargo test --no-default-features --features compression --all-targets
+cargo test --no-default-features --features cli,compression --all-targets
-cargo test --no-default-features --features decompression --all-targets
+cargo test --no-default-features --features cli,decompression --all-targets
+cargo test --no-default-features --all-targets
 ```
 
 Then run original compatibility tests from the repository root, starting with

rust/cli/Cargo.lock

@@ -2,6 +2,15 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "libc"
+version = "0.2.186"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "68ab91017fe16c622486840e4c83c9a37afeff978bd239b5293d61ece587de66"
+
 [[package]]
 name = "zstd-cli-rs"
 version = "0.1.0"
+dependencies = [
+ "libc",
+]

rust/cli/Cargo.toml

@@ -7,6 +7,13 @@ edition = "2021"
 crate-type = ["staticlib"]
 
 [features]
-default = ["compression", "decompression"]
+default = ["cli", "compression", "decompression"]
+# The command-line parser and dispatch layer, which requires the C fileio
+# backend at link time. Program archives enable it; C test binaries link a
+# helpers-only archive (timefn) built without it.
+cli = []
 compression = []
 decompression = []
+
+[dependencies]
+libc = "0.2"

rust/cli/src/lib.rs

@@ -1,2 +1,7 @@
+#[path = "../../src/benchfn.rs"]
+mod benchfn;
+#[path = "../../src/timefn.rs"]
+mod timefn;
+#[cfg(feature = "cli")]
 #[path = "../../src/zstd_cli.rs"]
 mod zstd_cli;

rust/src/benchfn.rs

@@ -0,0 +1,575 @@
+#![allow(non_camel_case_types)]
+#![allow(non_snake_case)]
+#![allow(clippy::missing_safety_doc)]
+
+//! Benchmark loop for arbitrary functions over a set of blocks.
+//!
+//! Port of `programs/benchfn.c`.  `BMK_benchFunction` measures one batch of
+//! runs; `BMK_benchTimedFn` repeats batches, growing the loop count until a
+//! run lasts long enough to be reported reliably against `run_ms`, within a
+//! `total_ms` budget tracked by `BMK_timedFnState_t`.
+//!
+//! ABI notes: `BMK_runOutcome_t` and `BMK_runTime_t` are returned by value
+//! across the C boundary and `BMK_benchParams_t` is passed by value, so all
+//! three are `repr(C)` mirrors of the `benchfn.h` layout, pinned by asserts
+//! here and in the C shim.  `BMK_timedFnState_t` is opaque to C, but
+//! `BMK_initStatic_timedFnState` guarantees it fits the 64-byte
+//! `BMK_timedFnState_shell`, and `BMK_createTimedFnState` uses `malloc` so
+//! creation and destruction stay interchangeable with C callers.
+
+use std::os::raw::{c_int, c_uint, c_void};
+use std::ptr;
+
+use crate::timefn::{PTime, UTIL_clockSpanNano, UTIL_getTime, UTIL_time_t};
+
+const TIMELOOP_NANOSEC: PTime = 1_000_000_000;
+
+/// Valid benchmark result (`BMK_runTime_t` in benchfn.h).
+#[repr(C)]
+#[derive(Clone, Copy, Debug)]
+pub struct BMK_runTime_t {
+    /// Time per iteration, over all blocks.
+    pub nanoSecPerRun: f64,
+    /// Sum of the benchmarked function's return values, first loop only.
+    pub sumOfReturn: usize,
+}
+
+/// Outcome variant of a benchmark run (`BMK_runOutcome_t` in benchfn.h):
+/// either a valid `BMK_runTime_t` or an error result. C callers treat it as
+/// opaque and use the accessor functions below.
+#[repr(C)]
+#[derive(Clone, Copy, Debug)]
+pub struct BMK_runOutcome_t {
+    pub internal_never_ever_use_directly: BMK_runTime_t,
+    pub error_result_never_ever_use_directly: usize,
+    pub error_tag_never_ever_use_directly: c_int,
+}
+
+// These mirror the static asserts in the programs/benchfn.c shim: the structs
+// cross the ABI by value, so field offsets must match the C header exactly.
+const _: () =
+    assert!(std::mem::offset_of!(BMK_runTime_t, sumOfReturn) == std::mem::size_of::<f64>());
+const _: () = assert!(
+    std::mem::offset_of!(BMK_runOutcome_t, error_result_never_ever_use_directly)
+        == std::mem::size_of::<BMK_runTime_t>()
+);
+const _: () = assert!(
+    std::mem::offset_of!(BMK_runOutcome_t, error_tag_never_ever_use_directly)
+        == std::mem::size_of::<BMK_runTime_t>() + std::mem::size_of::<usize>()
+);
+
+/// `size_t (*BMK_benchFn_t)(const void*, size_t, void*, size_t, void*)`
+pub type BMK_benchFn_t = Option<
+    unsafe extern "C" fn(
+        src: *const c_void,
+        srcSize: usize,
+        dst: *mut c_void,
+        dstCapacity: usize,
+        customPayload: *mut c_void,
+    ) -> usize,
+>;
+/// `size_t (*BMK_initFn_t)(void*)`
+pub type BMK_initFn_t = Option<unsafe extern "C" fn(initPayload: *mut c_void) -> usize>;
+/// `unsigned (*BMK_errorFn_t)(size_t)`
+pub type BMK_errorFn_t = Option<unsafe extern "C" fn(result: usize) -> c_uint>;
+
+/// Parameters of `BMK_benchFunction`, passed by value (`BMK_benchParams_t`).
+#[repr(C)]
+#[derive(Clone, Copy)]
+pub struct BMK_benchParams_t {
+    pub benchFn: BMK_benchFn_t,
+    pub benchPayload: *mut c_void,
+    pub initFn: BMK_initFn_t,
+    pub initPayload: *mut c_void,
+    pub errorFn: BMK_errorFn_t,
+    pub blockCount: usize,
+    pub srcBuffers: *const *const c_void,
+    pub srcSizes: *const usize,
+    pub dstBuffers: *const *mut c_void,
+    pub dstCapacities: *const usize,
+    pub blockResults: *mut usize,
+}
+
+/// Aborts, like benchfn.c's `CONTROL`, when an accessor is used on the wrong
+/// outcome variant.
+fn control(condition: bool) {
+    if !condition {
+        std::process::abort();
+    }
+}
+
+fn error_outcome(errorResult: usize) -> BMK_runOutcome_t {
+    BMK_runOutcome_t {
+        internal_never_ever_use_directly: BMK_runTime_t {
+            nanoSecPerRun: 0.0,
+            sumOfReturn: 0,
+        },
+        error_result_never_ever_use_directly: errorResult,
+        error_tag_never_ever_use_directly: 1,
+    }
+}
+
+fn valid_outcome(runTime: BMK_runTime_t) -> BMK_runOutcome_t {
+    BMK_runOutcome_t {
+        internal_never_ever_use_directly: runTime,
+        error_result_never_ever_use_directly: 0,
+        error_tag_never_ever_use_directly: 0,
+    }
+}
+
+/// Tells if the outcome carries a valid measurement.
+#[no_mangle]
+pub extern "C" fn BMK_isSuccessful_runOutcome(outcome: BMK_runOutcome_t) -> c_int {
+    c_int::from(outcome.error_tag_never_ever_use_directly == 0)
+}
+
+/// Extracts the measurement; aborts if the outcome is an error, so validity
+/// must be checked first with `BMK_isSuccessful_runOutcome`.
+#[no_mangle]
+pub extern "C" fn BMK_extract_runTime(outcome: BMK_runOutcome_t) -> BMK_runTime_t {
+    control(outcome.error_tag_never_ever_use_directly == 0);
+    outcome.internal_never_ever_use_directly
+}
+
+/// Extracts the faulty `benchFn` return value; aborts if the outcome is
+/// valid, so failure must be checked first.
+#[no_mangle]
+pub extern "C" fn BMK_extract_errorResult(outcome: BMK_runOutcome_t) -> usize {
+    control(outcome.error_tag_never_ever_use_directly != 0);
+    outcome.error_result_never_ever_use_directly
+}
+
+/// Runs `initFn` once, then `benchFn` `nbLoops` times over every block, and
+/// reports the mean time per loop.  On the first loop, per-block results are
+/// stored into `blockResults` (when provided) and checked with `errorFn`
+/// (when provided); the first failing block aborts the measurement and
+/// produces an error outcome carrying the faulty return value.
+#[no_mangle]
+pub unsafe extern "C" fn BMK_benchFunction(
+    p: BMK_benchParams_t,
+    mut nbLoops: c_uint,
+) -> BMK_runOutcome_t {
+    // Minimum nbLoops is 1.
+    nbLoops += c_uint::from(nbLoops == 0);
+
+    // Warm up and erase the result buffers.
+    for blockNb in 0..p.blockCount {
+        unsafe {
+            let dst = *p.dstBuffers.add(blockNb);
+            ptr::write_bytes(dst.cast::<u8>(), 0xE5, *p.dstCapacities.add(blockNb));
+        }
+    }
+
+    let benchFn = p.benchFn.expect("benchFn is mandatory");
+    let mut dstSize = 0usize;
+    let clockStart = UTIL_getTime();
+    if let Some(initFn) = p.initFn {
+        unsafe { initFn(p.initPayload) };
+    }
+    for loopNb in 0..nbLoops {
+        for blockNb in 0..p.blockCount {
+            let res = unsafe {
+                benchFn(
+                    *p.srcBuffers.add(blockNb),
+                    *p.srcSizes.add(blockNb),
+                    *p.dstBuffers.add(blockNb),
+                    *p.dstCapacities.add(blockNb),
+                    p.benchPayload,
+                )
+            };
+            if loopNb == 0 {
+                if !p.blockResults.is_null() {
+                    unsafe { *p.blockResults.add(blockNb) = res };
+                }
+                if let Some(errorFn) = p.errorFn {
+                    if unsafe { errorFn(res) } != 0 {
+                        return error_outcome(res);
+                    }
+                }
+                dstSize = dstSize.wrapping_add(res);
+            }
+        }
+    }
+
+    let totalTime = UTIL_clockSpanNano(clockStart);
+    valid_outcome(BMK_runTime_t {
+        nanoSecPerRun: totalTime as f64 / f64::from(nbLoops),
+        sumOfReturn: dstSize,
+    })
+}
+
+/// Benchmark session state (`struct BMK_timedFnState_s`), opaque to C.
+#[repr(C)]
+pub struct BMK_timedFnState_t {
+    timeSpent_ns: PTime,
+    timeBudget_ns: PTime,
+    runBudget_ns: PTime,
+    fastestRun: BMK_runTime_t,
+    nbLoops: c_uint,
+    coolTime: UTIL_time_t,
+}
+
+/// `BMK_TIMEDFNSTATE_SIZE` in benchfn.h: capacity of the caller-provided
+/// `BMK_timedFnState_shell`, which the state must always fit.
+const BMK_TIMEDFNSTATE_SIZE: usize = 64;
+const _: () = assert!(std::mem::size_of::<BMK_timedFnState_t>() <= BMK_TIMEDFNSTATE_SIZE);
+// The shell aligns via a `long long` member; the state must not need more.
+const _: () = assert!(std::mem::align_of::<BMK_timedFnState_t>() <= std::mem::align_of::<u64>());
+
+/// Allocates and initializes a benchmark session lasting a minimum of
+/// `total_ms`, paced at intervals of approximately `run_ms`.  Uses `malloc`
+/// so ownership stays interchangeable with the original C implementation.
+#[no_mangle]
+pub extern "C" fn BMK_createTimedFnState(
+    total_ms: c_uint,
+    run_ms: c_uint,
+) -> *mut BMK_timedFnState_t {
+    let state = unsafe { libc::malloc(std::mem::size_of::<BMK_timedFnState_t>()) }
+        .cast::<BMK_timedFnState_t>();
+    if state.is_null() {
+        return ptr::null_mut();
+    }
+    unsafe { BMK_resetTimedFnState(state, total_ms, run_ms) };
+    state
+}
+
+/// Releases a state obtained from `BMK_createTimedFnState`.
+#[no_mangle]
+pub unsafe extern "C" fn BMK_freeTimedFnState(state: *mut BMK_timedFnState_t) {
+    unsafe { libc::free(state.cast()) };
+}
+
+/// Places the session state into a caller-provided buffer, typically a
+/// `BMK_timedFnState_shell`.  Returns NULL when the buffer is missing, too
+/// small, or misaligned.
+#[no_mangle]
+pub unsafe extern "C" fn BMK_initStatic_timedFnState(
+    buffer: *mut c_void,
+    size: usize,
+    total_ms: c_uint,
+    run_ms: c_uint,
+) -> *mut BMK_timedFnState_t {
+    if buffer.is_null() {
+        return ptr::null_mut();
+    }
+    if size < std::mem::size_of::<BMK_timedFnState_t>() {
+        return ptr::null_mut();
+    }
+    if !(buffer as usize).is_multiple_of(std::mem::align_of::<BMK_timedFnState_t>()) {
+        return ptr::null_mut();
+    }
+    let state = buffer.cast::<BMK_timedFnState_t>();
+    unsafe { BMK_resetTimedFnState(state, total_ms, run_ms) };
+    state
+}
+
+/// Re-arms a session for a new benchmark of `total_ms`, paced at `run_ms`.
+#[no_mangle]
+pub unsafe extern "C" fn BMK_resetTimedFnState(
+    timedFnState: *mut BMK_timedFnState_t,
+    total_ms: c_uint,
+    run_ms: c_uint,
+) {
+    let total_ms = if total_ms == 0 { 1 } else { total_ms };
+    let mut run_ms = if run_ms == 0 { 1 } else { run_ms };
+    if run_ms > total_ms {
+        run_ms = total_ms;
+    }
+    let state = BMK_timedFnState_t {
+        timeSpent_ns: 0,
+        timeBudget_ns: PTime::from(total_ms) * TIMELOOP_NANOSEC / 1000,
+        runBudget_ns: PTime::from(run_ms) * TIMELOOP_NANOSEC / 1000,
+        fastestRun: BMK_runTime_t {
+            // Must be larger than any potential measurement.
+            nanoSecPerRun: TIMELOOP_NANOSEC as f64 * 2_000_000_000.0,
+            sumOfReturn: usize::MAX,
+        },
+        nbLoops: 1,
+        coolTime: UTIL_getTime(),
+    };
+    unsafe { timedFnState.write(state) };
+}
+
+/// Tells if the total time budget of the session is spent.  Also reports 1
+/// after `BMK_benchTimedFn` returned an error.
+#[no_mangle]
+pub unsafe extern "C" fn BMK_isCompleted_TimedFn(timedFnState: *const BMK_timedFnState_t) -> c_int {
+    let state = unsafe { &*timedFnState };
+    c_int::from(state.timeSpent_ns >= state.timeBudget_ns)
+}
+
+/// Runs one measurement supposed to last about `run_ms`, automatically
+/// scaling `nbLoops`.  Runs shorter than half the run budget are re-tried
+/// with a larger workload instead of being reported, limiting rounding-error
+/// risks; the best (fastest) qualifying run is returned.
+#[no_mangle]
+pub unsafe extern "C" fn BMK_benchTimedFn(
+    cont: *mut BMK_timedFnState_t,
+    p: BMK_benchParams_t,
+) -> BMK_runOutcome_t {
+    let cont = unsafe { &mut *cont };
+    let runBudget_ns = cont.runBudget_ns;
+    let runTimeMin_ns = runBudget_ns / 2;
+    let mut bestRunTime = cont.fastestRun;
+
+    loop {
+        let runResult = unsafe { BMK_benchFunction(p, cont.nbLoops) };
+
+        if BMK_isSuccessful_runOutcome(runResult) == 0 {
+            // Error: move out.
+            return runResult;
+        }
+
+        let newRunTime = BMK_extract_runTime(runResult);
+        let loopDuration_ns = newRunTime.nanoSecPerRun * f64::from(cont.nbLoops);
+
+        cont.timeSpent_ns = cont.timeSpent_ns.wrapping_add(loopDuration_ns as PTime);
+
+        // Estimate nbLoops for the next run to last approximately run_ms.
+        if loopDuration_ns > runBudget_ns as f64 / 50.0 {
+            let fastestRun_ns = bestRunTime.nanoSecPerRun.min(newRunTime.nanoSecPerRun);
+            cont.nbLoops = ((runBudget_ns as f64 / fastestRun_ns) as c_uint).wrapping_add(1);
+        } else {
+            // Previous run was too short: blindly increase workload by a
+            // x10 multiplier.
+            const MULTIPLIER: c_uint = 10;
+            debug_assert!(cont.nbLoops < c_uint::MAX / MULTIPLIER); // avoid overflow
+            cont.nbLoops = cont.nbLoops.wrapping_mul(MULTIPLIER);
+        }
+
+        if loopDuration_ns < runTimeMin_ns as f64 {
+            // Don't report results when the run time was too small, which
+            // increases the risk of rounding errors.
+            continue;
+        }
+        if newRunTime.nanoSecPerRun < bestRunTime.nanoSecPerRun {
+            bestRunTime = newRunTime;
+        }
+        return valid_outcome(bestRunTime);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// Test payload observed through `benchPayload`/`initPayload` pointers.
+    #[derive(Default)]
+    struct CallLog {
+        bench_calls: usize,
+        init_calls: usize,
+    }
+
+    /// Counts invocations and reports `srcSize`, like a size-preserving codec.
+    unsafe extern "C" fn counting_bench_fn(
+        _src: *const c_void,
+        srcSize: usize,
+        _dst: *mut c_void,
+        _dstCapacity: usize,
+        payload: *mut c_void,
+    ) -> usize {
+        let log = unsafe { &mut *payload.cast::<CallLog>() };
+        log.bench_calls += 1;
+        srcSize
+    }
+
+    unsafe extern "C" fn counting_init_fn(payload: *mut c_void) -> usize {
+        let log = unsafe { &mut *payload.cast::<CallLog>() };
+        log.init_calls += 1;
+        0
+    }
+
+    /// Flags results of 5 bytes and above as errors.
+    unsafe extern "C" fn error_on_5(result: usize) -> c_uint {
+        c_uint::from(result >= 5)
+    }
+
+    struct Fixture {
+        srcs: Vec<Vec<u8>>,
+        dsts: Vec<Vec<u8>>,
+        src_ptrs: Vec<*const c_void>,
+        src_sizes: Vec<usize>,
+        dst_ptrs: Vec<*mut c_void>,
+        dst_capacities: Vec<usize>,
+        block_results: Vec<usize>,
+        log: CallLog,
+    }
+
+    impl Fixture {
+        fn new(block_sizes: &[usize]) -> Box<Self> {
+            let srcs: Vec<Vec<u8>> = block_sizes.iter().map(|size| vec![0u8; *size]).collect();
+            let mut dsts: Vec<Vec<u8>> = block_sizes.iter().map(|size| vec![0u8; *size]).collect();
+            let src_ptrs = srcs.iter().map(|src| src.as_ptr().cast()).collect();
+            let src_sizes = srcs.iter().map(Vec::len).collect();
+            let dst_ptrs = dsts.iter_mut().map(|dst| dst.as_mut_ptr().cast()).collect();
+            let dst_capacities = dsts.iter().map(Vec::len).collect();
+            let block_results = vec![0usize; block_sizes.len()];
+            Box::new(Self {
+                srcs,
+                dsts,
+                src_ptrs,
+                src_sizes,
+                dst_ptrs,
+                dst_capacities,
+                block_results,
+                log: CallLog::default(),
+            })
+        }
+
+        fn params(&mut self, errorFn: BMK_errorFn_t) -> BMK_benchParams_t {
+            let payload: *mut CallLog = &mut self.log;
+            BMK_benchParams_t {
+                benchFn: Some(counting_bench_fn),
+                benchPayload: payload.cast(),
+                initFn: Some(counting_init_fn),
+                initPayload: payload.cast(),
+                errorFn,
+                blockCount: self.srcs.len(),
+                srcBuffers: self.src_ptrs.as_ptr(),
+                srcSizes: self.src_sizes.as_ptr(),
+                dstBuffers: self.dst_ptrs.as_ptr(),
+                dstCapacities: self.dst_capacities.as_ptr(),
+                blockResults: self.block_results.as_mut_ptr(),
+            }
+        }
+    }
+
+    #[test]
+    fn bench_function_accounts_loops_blocks_and_first_loop_results() {
+        let mut fixture = Fixture::new(&[3, 8]);
+        let params = fixture.params(None);
+
+        let outcome = unsafe { BMK_benchFunction(params, 4) };
+
+        assert_eq!(BMK_isSuccessful_runOutcome(outcome), 1);
+        let run_time = BMK_extract_runTime(outcome);
+        // benchFn ran nbLoops times over each block; initFn ran once.
+        assert_eq!(fixture.log.bench_calls, 4 * 2);
+        assert_eq!(fixture.log.init_calls, 1);
+        // sumOfReturn and blockResults reflect the first loop only.
+        assert_eq!(run_time.sumOfReturn, 3 + 8);
+        assert_eq!(fixture.block_results, vec![3, 8]);
+        assert!(run_time.nanoSecPerRun >= 0.0);
+    }
+
+    #[test]
+    fn bench_function_treats_zero_loops_as_one_and_warms_up_buffers() {
+        let mut fixture = Fixture::new(&[4]);
+        let params = fixture.params(None);
+
+        let outcome = unsafe { BMK_benchFunction(params, 0) };
+
+        assert_eq!(BMK_isSuccessful_runOutcome(outcome), 1);
+        assert_eq!(fixture.log.bench_calls, 1);
+        // The result buffer was erased with the 0xE5 warm-up pattern.
+        assert_eq!(fixture.dsts[0], vec![0xE5; 4]);
+    }
+
+    #[test]
+    fn bench_function_reports_the_first_failing_block() {
+        let mut fixture = Fixture::new(&[3, 5, 7]);
+        let params = fixture.params(Some(error_on_5));
+
+        let outcome = unsafe { BMK_benchFunction(params, 10) };
+
+        assert_eq!(BMK_isSuccessful_runOutcome(outcome), 0);
+        assert_eq!(BMK_extract_errorResult(outcome), 5);
+        // Execution stopped at the failing block, before the third one.
+        assert_eq!(fixture.log.bench_calls, 2);
+        // blockResults were recorded up to and including the failure.
+        assert_eq!(fixture.block_results[..2], [3, 5]);
+    }
+
+    #[test]
+    fn reset_clamps_budgets_and_rearms_the_loop_counter() {
+        let state = BMK_createTimedFnState(0, 7);
+        assert!(!state.is_null());
+
+        {
+            let state = unsafe { &*state };
+            // total_ms 0 becomes 1ms, and run_ms is clamped to total_ms.
+            assert_eq!(state.timeBudget_ns, 1_000_000);
+            assert_eq!(state.runBudget_ns, 1_000_000);
+            assert_eq!(state.nbLoops, 1);
+            assert_eq!(state.timeSpent_ns, 0);
+            assert_eq!(state.fastestRun.sumOfReturn, usize::MAX);
+        }
+        assert_eq!(unsafe { BMK_isCompleted_TimedFn(state) }, 0);
+
+        unsafe { BMK_resetTimedFnState(state, 2_000, 500) };
+        {
+            let state = unsafe { &*state };
+            assert_eq!(state.timeBudget_ns, 2_000_000_000);
+            assert_eq!(state.runBudget_ns, 500_000_000);
+        }
+
+        unsafe { BMK_freeTimedFnState(state) };
+    }
+
+    #[test]
+    fn static_state_initialization_validates_its_buffer() {
+        let mut shell = [0u64; BMK_TIMEDFNSTATE_SIZE / 8];
+        let buffer: *mut c_void = shell.as_mut_ptr().cast();
+
+        // A properly sized and aligned buffer is accepted.
+        let state = unsafe { BMK_initStatic_timedFnState(buffer, 64, 1_000, 100) };
+        assert!(!state.is_null());
+        assert_eq!(unsafe { BMK_isCompleted_TimedFn(state) }, 0);
+
+        // NULL, undersized, and misaligned buffers are rejected.
+        let too_small = std::mem::size_of::<BMK_timedFnState_t>() - 1;
+        unsafe {
+            assert!(BMK_initStatic_timedFnState(ptr::null_mut(), 64, 1, 1).is_null());
+            assert!(BMK_initStatic_timedFnState(buffer, too_small, 1, 1).is_null());
+            assert!(
+                BMK_initStatic_timedFnState(buffer.cast::<u8>().add(1).cast(), 63, 1, 1).is_null()
+            );
+        }
+    }
+
+    #[test]
+    fn timed_runs_grow_the_workload_and_spend_the_budget() {
+        let mut fixture = Fixture::new(&[16]);
+        let params = fixture.params(None);
+        let state = BMK_createTimedFnState(4, 2);
+        assert!(!state.is_null());
+
+        let mut rounds = 0usize;
+        while unsafe { BMK_isCompleted_TimedFn(state) } == 0 {
+            let outcome = unsafe { BMK_benchTimedFn(state, params) };
+            assert_eq!(BMK_isSuccessful_runOutcome(outcome), 1);
+            let run_time = BMK_extract_runTime(outcome);
+            assert_eq!(run_time.sumOfReturn, 16);
+            rounds += 1;
+            assert!(rounds < 1_000, "the time budget must eventually be spent");
+        }
+
+        {
+            let state = unsafe { &*state };
+            // A reported run had to last at least runBudget/2, which is only
+            // reachable for this trivial function with a grown loop counter.
+            assert!(state.nbLoops > 1);
+            assert!(state.timeSpent_ns >= state.timeBudget_ns);
+        }
+        // Every reported outcome came from a run of >= runBudget/2, and the
+        // budget accounting matches BMK_isCompleted_TimedFn.
+        assert!(rounds >= 1);
+        assert!(fixture.log.bench_calls >= rounds);
+
+        unsafe { BMK_freeTimedFnState(state) };
+    }
+
+    #[test]
+    fn timed_runs_propagate_errors_without_aborting() {
+        let mut fixture = Fixture::new(&[9]);
+        let params = fixture.params(Some(error_on_5));
+        let state = BMK_createTimedFnState(1_000, 100);
+
+        let outcome = unsafe { BMK_benchTimedFn(state, params) };
+
+        assert_eq!(BMK_isSuccessful_runOutcome(outcome), 0);
+        assert_eq!(BMK_extract_errorResult(outcome), 9);
+
+        unsafe { BMK_freeTimedFnState(state) };
+    }
+}

rust/src/legacy/mod.rs

@@ -0,0 +1,40 @@
+//! Frozen decoders for the legacy zstd formats (v0.1 through v0.7).
+//!
+//! Frozen-decoder policy
+//! =====================
+//!
+//! Each `lib/legacy/zstd_v0N.c` translation unit is a self-contained snapshot
+//! of the entropy coders and frame logic of that historical release.  The
+//! Rust ports mirror that property:
+//!
+//! - Every version keeps its own frozen FSE/Huff0 and frame logic.  The
+//!   modern `fse_decompress`, `huf_decompress`, `bitstream`, or `mem`
+//!   modules must NOT be reused here, and legacy versions must not share
+//!   code with each other, even where functions look identical.  The legacy
+//!   formats are frozen; the modern modules keep evolving.
+//! - Ports are line-by-line translations of the corresponding C file: same
+//!   table layouts, same arithmetic, same error codes.  Outputs must be
+//!   byte-identical to the C implementation, including error behavior.
+//! - The only shared dependency is `crate::errors`, because the C files
+//!   include `error_private.h` for the public `ZSTD_ErrorCode` values.
+//!
+//! Registration
+//! ============
+//!
+//! Cargo features `legacy-v01` .. `legacy-v07` are all declared in
+//! `Cargo.toml`.  The build systems always pass the feature list derived
+//! from the C configuration (`ZSTD_LEGACY_SUPPORT=N` enables versions N
+//! and newer), so a feature may be enabled before its port exists.  A version
+//! without a Rust module simply stays implemented by its C file.
+//!
+//! To port version `v0N`: add `zstd_v0N.rs` next to this file, reduce
+//! `lib/legacy/zstd_v0N.c` to a declaration-only shim, and register the
+//! module here with exactly one line:
+//!
+//! ```text
+//! #[cfg(feature = "legacy-v0N")]
+//! pub mod zstd_v0N;
+//! ```
+
+#[cfg(feature = "legacy-v01")]
+pub mod zstd_v01;

rust/src/legacy/zstd_v01.rs

@@ -0,0 +1,2354 @@
+#![allow(non_snake_case)]
+
+//! Frozen decoder for the zstd v0.1 format.
+//!
+//! This is a line-by-line port of `lib/legacy/zstd_v01.c`: the same table
+//! layouts, the same arithmetic, and the same error codes.  The C file is a
+//! self-contained snapshot of the v0.1-era FSE and Huff0 coders, so this
+//! module deliberately reimplements them instead of reusing the modern
+//! `fse_decompress`/`huf_decompress` modules (see `legacy/mod.rs` for the
+//! frozen-decoder policy).  The only shared dependency is `crate::errors`,
+//! mirroring the C file's `error_private.h` include.
+//!
+//! The streaming `ZSTDv01_Dctx` state lives entirely in Rust; C callers only
+//! ever hold an opaque pointer to it.  It is allocated with `libc::malloc`
+//! and released with `libc::free`, exactly like the original C context.
+
+use crate::errors::{ERR_isError, ZstdErrorCode, ERROR};
+use std::os::raw::{c_uint, c_void};
+use std::ptr;
+
+/* ******************************************
+ *  Error management (frozen v0.1 FSE codes)
+ ********************************************/
+/* FSE_LIST_ERRORS in zstd_v01.c; values are returned as `(size_t)-code`. */
+const FSE_ERROR_GENERIC: usize = 1;
+const FSE_ERROR_TABLELOG_TOO_LARGE: usize = 2;
+const FSE_ERROR_MAX_SYMBOL_VALUE_TOO_LARGE: usize = 3;
+const FSE_ERROR_MAX_SYMBOL_VALUE_TOO_SMALL: usize = 4;
+const FSE_ERROR_DST_SIZE_TOO_SMALL: usize = 5;
+const FSE_ERROR_SRC_SIZE_WRONG: usize = 6;
+const FSE_ERROR_CORRUPTION_DETECTED: usize = 7;
+const FSE_ERROR_MAX_CODE: usize = 8;
+
+#[inline]
+fn fse_error(code: usize) -> usize {
+    code.wrapping_neg()
+}
+
+#[inline]
+fn fse_is_error(code: usize) -> bool {
+    code > fse_error(FSE_ERROR_MAX_CODE)
+}
+
+/* ******************************************
+ *  Tuning parameters (frozen)
+ ********************************************/
+const FSE_MAX_MEMORY_USAGE: u32 = 14;
+const FSE_MAX_SYMBOL_VALUE: u32 = 255;
+
+const FSE_MAX_TABLELOG: u32 = FSE_MAX_MEMORY_USAGE - 2;
+const FSE_MIN_TABLELOG: u32 = 5;
+const FSE_TABLELOG_ABSOLUTE_MAX: u32 = 15;
+
+const HUF_MAX_SYMBOL_VALUE: u32 = 255;
+const HUF_MAX_TABLELOG: u32 = 12;
+const HUF_ABSOLUTEMAX_TABLELOG: u32 = 16;
+
+const IS_32BITS: bool = std::mem::size_of::<usize>() == 4;
+const USIZE_BITS: u32 = usize::BITS;
+
+/* ******************************************
+ *  Memory I/O (FSE_read* / ZSTD_read* helpers)
+ ********************************************/
+#[inline]
+unsafe fn fse_read_le16(mem_ptr: *const u8) -> u16 {
+    u16::from_le_bytes(ptr::read_unaligned(mem_ptr as *const [u8; 2]))
+}
+
+#[inline]
+unsafe fn fse_read_le32(mem_ptr: *const u8) -> u32 {
+    u32::from_le_bytes(ptr::read_unaligned(mem_ptr as *const [u8; 4]))
+}
+
+#[inline]
+unsafe fn fse_read_le64(mem_ptr: *const u8) -> u64 {
+    u64::from_le_bytes(ptr::read_unaligned(mem_ptr as *const [u8; 8]))
+}
+
+#[inline]
+unsafe fn fse_read_lest(mem_ptr: *const u8) -> usize {
+    if IS_32BITS {
+        fse_read_le32(mem_ptr) as usize
+    } else {
+        fse_read_le64(mem_ptr) as usize
+    }
+}
+
+/// `FSE_highbit32`; the caller guarantees `val != 0`, as in C.
+#[inline]
+fn fse_highbit32(val: u32) -> u32 {
+    val.leading_zeros() ^ 31
+}
+
+/* ******************************************
+ *  FSE structures
+ ********************************************/
+#[repr(C)]
+#[derive(Clone, Copy)]
+struct FseDecode {
+    new_state: u16,
+    symbol: u8,
+    nb_bits: u8,
+}
+
+#[repr(C)]
+struct FseDTableHeader {
+    table_log: u16,
+    fast_mode: u16,
+}
+
+struct FseDStream {
+    bit_container: usize,
+    bits_consumed: u32,
+    ptr: *const u8,
+    start: *const u8,
+}
+
+struct FseDState {
+    state: usize,
+    table: *const FseDecode,
+}
+
+const FSE_DSTREAM_UNFINISHED: u32 = 0;
+const FSE_DSTREAM_END_OF_BUFFER: u32 = 1;
+const FSE_DSTREAM_COMPLETED: u32 = 2;
+const FSE_DSTREAM_TOO_FAR: u32 = 3;
+
+#[inline]
+fn fse_table_step(table_size: u32) -> u32 {
+    (table_size >> 1) + (table_size >> 3) + 3
+}
+
+/* An FSE_DTable is an opaque u32 array: one header word followed by
+ * `1 << tableLog` FseDecode entries, exactly as in C. */
+unsafe fn fse_build_dtable(
+    dt: *mut u32,
+    normalized_counter: *const i16,
+    max_symbol_value: u32,
+    table_log: u32,
+) -> usize {
+    let dtable_h = dt as *mut FseDTableHeader;
+    let table_decode = dt.add(1) as *mut FseDecode;
+
+    /* Sanity checks */
+    if max_symbol_value > FSE_MAX_SYMBOL_VALUE {
+        return fse_error(FSE_ERROR_MAX_SYMBOL_VALUE_TOO_LARGE);
+    }
+    if table_log > FSE_MAX_TABLELOG {
+        return fse_error(FSE_ERROR_TABLELOG_TOO_LARGE);
+    }
+
+    let table_size: u32 = 1 << table_log;
+    let table_mask = table_size - 1;
+    let step = fse_table_step(table_size);
+    let mut symbol_next = [0u16; (FSE_MAX_SYMBOL_VALUE + 1) as usize];
+    let mut position: u32 = 0;
+    let mut high_threshold = table_size - 1;
+    let large_limit = (1i32 << (table_log - 1)) as i16;
+    let mut no_large: u32 = 1;
+
+    /* Init, lay down lowprob symbols */
+    (*dtable_h).table_log = table_log as u16;
+    for s in 0..=max_symbol_value {
+        let count = *normalized_counter.add(s as usize);
+        if count == -1 {
+            (*table_decode.add(high_threshold as usize)).symbol = s as u8;
+            high_threshold = high_threshold.wrapping_sub(1);
+            symbol_next[s as usize] = 1;
+        } else {
+            if count >= large_limit {
+                no_large = 0;
+            }
+            symbol_next[s as usize] = count as u16;
+        }
+    }
+
+    /* Spread symbols */
+    for s in 0..=max_symbol_value {
+        let count = *normalized_counter.add(s as usize);
+        let mut i = 0i32;
+        while i < count as i32 {
+            (*table_decode.add(position as usize)).symbol = s as u8;
+            position = (position + step) & table_mask;
+            while position > high_threshold {
+                position = (position + step) & table_mask; /* lowprob area */
+            }
+            i += 1;
+        }
+    }
+
+    if position != 0 {
+        /* position must reach all cells once, otherwise normalizedCounter is incorrect */
+        return fse_error(FSE_ERROR_GENERIC);
+    }
+
+    /* Build Decoding table */
+    for i in 0..table_size as usize {
+        let symbol = (*table_decode.add(i)).symbol;
+        let next_state = symbol_next[symbol as usize];
+        symbol_next[symbol as usize] = next_state.wrapping_add(1);
+        let nb_bits = (table_log - fse_highbit32(next_state as u32)) as u8;
+        (*table_decode.add(i)).nb_bits = nb_bits;
+        (*table_decode.add(i)).new_state =
+            (((next_state as u32) << nb_bits).wrapping_sub(table_size)) as u16;
+    }
+
+    (*dtable_h).fast_mode = no_large as u16;
+    0
+}
+
+/* ******************************************
+ *  FSE header bitstream (FSE_readNCount)
+ ********************************************/
+unsafe fn fse_read_ncount(
+    normalized_counter: *mut i16,
+    max_sv_ptr: &mut u32,
+    table_log_ptr: &mut u32,
+    header_buffer: *const u8,
+    hb_size: usize,
+) -> usize {
+    let istart = header_buffer;
+    let iend_addr = (istart as usize).wrapping_add(hb_size);
+    let mut ip = istart;
+    let mut charnum: u32 = 0;
+    let mut previous0 = false;
+
+    if hb_size < 4 {
+        return fse_error(FSE_ERROR_SRC_SIZE_WRONG);
+    }
+    let mut bit_stream = fse_read_le32(ip);
+    let mut nb_bits: i32 = ((bit_stream & 0xF) + FSE_MIN_TABLELOG) as i32; /* extract tableLog */
+    if nb_bits > FSE_TABLELOG_ABSOLUTE_MAX as i32 {
+        return fse_error(FSE_ERROR_TABLELOG_TOO_LARGE);
+    }
+    bit_stream >>= 4;
+    let mut bit_count: i32 = 4;
+    *table_log_ptr = nb_bits as u32;
+    let mut remaining: i32 = (1 << nb_bits) + 1;
+    let mut threshold: i32 = 1 << nb_bits;
+    nb_bits += 1;
+
+    while remaining > 1 && charnum <= *max_sv_ptr {
+        if previous0 {
+            let mut n0 = charnum;
+            while (bit_stream & 0xFFFF) == 0xFFFF {
+                n0 += 24;
+                if (ip as usize) < iend_addr.wrapping_sub(5) {
+                    ip = ip.add(2);
+                    bit_stream = fse_read_le32(ip).wrapping_shr(bit_count as u32);
+                } else {
+                    bit_stream >>= 16;
+                    bit_count += 16;
+                }
+            }
+            while (bit_stream & 3) == 3 {
+                n0 += 3;
+                bit_stream >>= 2;
+                bit_count += 2;
+            }
+            n0 += bit_stream & 3;
+            bit_count += 2;
+            if n0 > *max_sv_ptr {
+                return fse_error(FSE_ERROR_MAX_SYMBOL_VALUE_TOO_SMALL);
+            }
+            while charnum < n0 {
+                *normalized_counter.add(charnum as usize) = 0;
+                charnum += 1;
+            }
+            if (ip as usize) <= iend_addr.wrapping_sub(7)
+                || (ip as usize).wrapping_add((bit_count >> 3) as usize)
+                    <= iend_addr.wrapping_sub(4)
+            {
+                ip = ip.add((bit_count >> 3) as usize);
+                bit_count &= 7;
+                bit_stream = fse_read_le32(ip).wrapping_shr(bit_count as u32);
+            } else {
+                bit_stream >>= 2;
+            }
+        }
+        {
+            let max: i16 = ((2 * threshold - 1) - remaining) as i16;
+            let mut count: i16;
+
+            if (bit_stream & (threshold - 1) as u32) < max as i32 as u32 {
+                count = (bit_stream & (threshold - 1) as u32) as u16 as i16;
+                bit_count += nb_bits - 1;
+            } else {
+                count = (bit_stream & (2 * threshold - 1) as u32) as u16 as i16;
+                if count as i32 >= threshold {
+                    count = ((count as i32) - (max as i32)) as i16;
+                }
+                bit_count += nb_bits;
+            }
+
+            count = count.wrapping_sub(1); /* extra accuracy */
+            remaining -= (count as i32).abs();
+            *normalized_counter.add(charnum as usize) = count;
+            charnum += 1;
+            previous0 = count == 0;
+            while remaining < threshold {
+                nb_bits -= 1;
+                threshold >>= 1;
+            }
+
+            if (ip as usize) <= iend_addr.wrapping_sub(7)
+                || (ip as usize).wrapping_add((bit_count >> 3) as usize)
+                    <= iend_addr.wrapping_sub(4)
+            {
+                ip = ip.add((bit_count >> 3) as usize);
+                bit_count &= 7;
+            } else {
+                bit_count -=
+                    (8 * (iend_addr.wrapping_sub(4) as isize - ip as usize as isize)) as i32;
+                ip = (iend_addr - 4) as *const u8;
+            }
+            bit_stream = fse_read_le32(ip).wrapping_shr((bit_count & 31) as u32);
+        }
+    }
+    if remaining != 1 {
+        return fse_error(FSE_ERROR_GENERIC);
+    }
+    *max_sv_ptr = charnum - 1;
+
+    ip = ip.wrapping_offset(((bit_count + 7) >> 3) as isize);
+    if (ip as usize).wrapping_sub(istart as usize) > hb_size {
+        return fse_error(FSE_ERROR_SRC_SIZE_WRONG);
+    }
+    (ip as usize).wrapping_sub(istart as usize)
+}
+
+/* ******************************************
+ *  FSE decompression, byte symbols
+ ********************************************/
+unsafe fn fse_build_dtable_rle(dt: *mut u32, symbol_value: u8) -> usize {
+    let dtable_h = dt as *mut FseDTableHeader;
+    let cell = dt.add(1) as *mut FseDecode;
+
+    (*dtable_h).table_log = 0;
+    (*dtable_h).fast_mode = 0;
+
+    (*cell).new_state = 0;
+    (*cell).symbol = symbol_value;
+    (*cell).nb_bits = 0;
+
+    0
+}
+
+unsafe fn fse_build_dtable_raw(dt: *mut u32, nb_bits: u32) -> usize {
+    let dtable_h = dt as *mut FseDTableHeader;
+    let dinfo = dt.add(1) as *mut FseDecode;
+
+    /* Sanity checks */
+    if nb_bits < 1 {
+        return fse_error(FSE_ERROR_GENERIC); /* min size */
+    }
+    let table_size: u32 = 1 << nb_bits;
+    let table_mask = table_size - 1;
+    let max_symbol_value = table_mask;
+
+    (*dtable_h).table_log = nb_bits as u16;
+    (*dtable_h).fast_mode = 1;
+    for s in 0..=max_symbol_value {
+        let cell = dinfo.add(s as usize);
+        (*cell).new_state = 0;
+        (*cell).symbol = s as u8;
+        (*cell).nb_bits = nb_bits as u8;
+    }
+
+    0
+}
+
+unsafe fn fse_init_dstream(
+    bit_d: &mut FseDStream,
+    src_buffer: *const u8,
+    src_size: usize,
+) -> usize {
+    let word = std::mem::size_of::<usize>();
+    if src_size < 1 {
+        return fse_error(FSE_ERROR_SRC_SIZE_WRONG);
+    }
+
+    if src_size >= word {
+        bit_d.start = src_buffer;
+        bit_d.ptr = src_buffer.add(src_size - word);
+        bit_d.bit_container = fse_read_lest(bit_d.ptr);
+        let contain32 = *src_buffer.add(src_size - 1) as u32;
+        if contain32 == 0 {
+            return fse_error(FSE_ERROR_GENERIC); /* stop bit not present */
+        }
+        bit_d.bits_consumed = 8 - fse_highbit32(contain32);
+    } else {
+        bit_d.start = src_buffer;
+        bit_d.ptr = bit_d.start;
+        bit_d.bit_container = *bit_d.start as usize;
+        /* C switch with fallthrough over srcSize 7..2 */
+        if src_size >= 7 {
+            bit_d.bit_container += (*src_buffer.add(6) as usize) << (USIZE_BITS as usize - 16);
+        }
+        if src_size >= 6 {
+            bit_d.bit_container += (*src_buffer.add(5) as usize) << (USIZE_BITS as usize - 24);
+        }
+        if src_size >= 5 {
+            bit_d.bit_container += (*src_buffer.add(4) as usize) << (USIZE_BITS as usize - 32);
+        }
+        if src_size >= 4 {
+            bit_d.bit_container += (*src_buffer.add(3) as usize) << 24;
+        }
+        if src_size >= 3 {
+            bit_d.bit_container += (*src_buffer.add(2) as usize) << 16;
+        }
+        if src_size >= 2 {
+            bit_d.bit_container += (*src_buffer.add(1) as usize) << 8;
+        }
+        let contain32 = *src_buffer.add(src_size - 1) as u32;
+        if contain32 == 0 {
+            return fse_error(FSE_ERROR_GENERIC); /* stop bit not present */
+        }
+        bit_d.bits_consumed = 8 - fse_highbit32(contain32);
+        bit_d.bits_consumed += ((word - src_size) * 8) as u32;
+    }
+
+    src_size
+}
+
+#[inline]
+unsafe fn fse_look_bits(bit_d: &FseDStream, nb_bits: u32) -> usize {
+    let bit_mask = USIZE_BITS - 1;
+    ((bit_d.bit_container << (bit_d.bits_consumed & bit_mask)) >> 1)
+        >> (bit_mask.wrapping_sub(nb_bits) & bit_mask)
+}
+
+#[inline]
+unsafe fn fse_look_bits_fast(bit_d: &FseDStream, nb_bits: u32) -> usize {
+    /* only if nb_bits >= 1 */
+    let bit_mask = USIZE_BITS - 1;
+    (bit_d.bit_container << (bit_d.bits_consumed & bit_mask))
+        >> ((bit_mask + 1).wrapping_sub(nb_bits) & bit_mask)
+}
+
+#[inline]
+fn fse_skip_bits(bit_d: &mut FseDStream, nb_bits: u32) {
+    bit_d.bits_consumed = bit_d.bits_consumed.wrapping_add(nb_bits);
+}
+
+#[inline]
+unsafe fn fse_read_bits(bit_d: &mut FseDStream, nb_bits: u32) -> usize {
+    let value = fse_look_bits(bit_d, nb_bits);
+    fse_skip_bits(bit_d, nb_bits);
+    value
+}
+
+#[inline]
+unsafe fn fse_read_bits_fast(bit_d: &mut FseDStream, nb_bits: u32) -> usize {
+    /* only if nb_bits >= 1 */
+    let value = fse_look_bits_fast(bit_d, nb_bits);
+    fse_skip_bits(bit_d, nb_bits);
+    value
+}
+
+unsafe fn fse_reload_dstream(bit_d: &mut FseDStream) -> u32 {
+    let word = std::mem::size_of::<usize>();
+    if bit_d.bits_consumed > (word * 8) as u32 {
+        /* should never happen */
+        return FSE_DSTREAM_TOO_FAR;
+    }
+
+    if (bit_d.ptr as usize) >= (bit_d.start as usize).wrapping_add(word) {
+        bit_d.ptr = bit_d.ptr.sub((bit_d.bits_consumed >> 3) as usize);
+        bit_d.bits_consumed &= 7;
+        bit_d.bit_container = fse_read_lest(bit_d.ptr);
+        return FSE_DSTREAM_UNFINISHED;
+    }
+    if bit_d.ptr == bit_d.start {
+        if bit_d.bits_consumed < (word * 8) as u32 {
+            return FSE_DSTREAM_END_OF_BUFFER;
+        }
+        return FSE_DSTREAM_COMPLETED;
+    }
+    {
+        let mut nb_bytes = bit_d.bits_consumed >> 3;
+        let mut result = FSE_DSTREAM_UNFINISHED;
+        if (bit_d.ptr as usize).wrapping_sub(nb_bytes as usize) < (bit_d.start as usize) {
+            nb_bytes = ((bit_d.ptr as usize) - (bit_d.start as usize)) as u32; /* ptr > start */
+            result = FSE_DSTREAM_END_OF_BUFFER;
+        }
+        bit_d.ptr = bit_d.ptr.sub(nb_bytes as usize);
+        bit_d.bits_consumed -= nb_bytes * 8;
+        bit_d.bit_container = fse_read_lest(bit_d.ptr); /* reminder : srcSize > sizeof(bitD) */
+        result
+    }
+}
+
+unsafe fn fse_init_dstate(d_state: &mut FseDState, bit_d: &mut FseDStream, dt: *const u32) {
+    let dtable_h = dt as *const FseDTableHeader;
+    d_state.state = fse_read_bits(bit_d, (*dtable_h).table_log as u32);
+    fse_reload_dstream(bit_d);
+    d_state.table = dt.add(1) as *const FseDecode;
+}
+
+unsafe fn fse_decode_symbol(d_state: &mut FseDState, bit_d: &mut FseDStream) -> u8 {
+    let d_info = *d_state.table.add(d_state.state);
+    let low_bits = fse_read_bits(bit_d, d_info.nb_bits as u32);
+    d_state.state = (d_info.new_state as usize).wrapping_add(low_bits);
+    d_info.symbol
+}
+
+unsafe fn fse_decode_symbol_fast(d_state: &mut FseDState, bit_d: &mut FseDStream) -> u8 {
+    let d_info = *d_state.table.add(d_state.state);
+    let low_bits = fse_read_bits_fast(bit_d, d_info.nb_bits as u32);
+    d_state.state = (d_info.new_state as usize).wrapping_add(low_bits);
+    d_info.symbol
+}
+
+#[inline]
+fn fse_end_of_dstream(bit_d: &FseDStream) -> bool {
+    bit_d.ptr == bit_d.start && bit_d.bits_consumed == USIZE_BITS
+}
+
+#[inline]
+fn fse_end_of_dstate(d_state: &FseDState) -> bool {
+    d_state.state == 0
+}
+
+unsafe fn fse_decompress_using_dtable_generic(
+    dst: *mut u8,
+    max_dst_size: usize,
+    c_src: *const u8,
+    c_src_size: usize,
+    dt: *const u32,
+    fast: bool,
+) -> usize {
+    let ostart = dst;
+    let mut op = ostart;
+    let omax_addr = (op as usize).wrapping_add(max_dst_size);
+    let olimit_addr = omax_addr.wrapping_sub(3);
+
+    let mut bit_d = FseDStream {
+        bit_container: 0,
+        bits_consumed: 0,
+        ptr: ptr::null(),
+        start: ptr::null(),
+    };
+    let mut state1 = FseDState {
+        state: 0,
+        table: ptr::null(),
+    };
+    let mut state2 = FseDState {
+        state: 0,
+        table: ptr::null(),
+    };
+
+    /* Init */
+    let error_code = fse_init_dstream(&mut bit_d, c_src, c_src_size);
+    if fse_is_error(error_code) {
+        return error_code;
+    }
+
+    fse_init_dstate(&mut state1, &mut bit_d, dt);
+    fse_init_dstate(&mut state2, &mut bit_d, dt);
+
+    macro_rules! fse_getsymbol {
+        ($state:expr) => {
+            if fast {
+                fse_decode_symbol_fast($state, &mut bit_d)
+            } else {
+                fse_decode_symbol($state, &mut bit_d)
+            }
+        };
+    }
+
+    /* Constant conditions from the C source; on 64-bit both are false, on
+     * 32-bit only the *4 variant reloads. */
+    const RELOAD_2: bool = FSE_MAX_TABLELOG * 2 + 7 > USIZE_BITS;
+    const RELOAD_4: bool = FSE_MAX_TABLELOG * 4 + 7 > USIZE_BITS;
+
+    /* 4 symbols per loop */
+    while fse_reload_dstream(&mut bit_d) == FSE_DSTREAM_UNFINISHED && (op as usize) < olimit_addr {
+        *op = fse_getsymbol!(&mut state1);
+
+        if RELOAD_2 {
+            /* This test must be static */
+            fse_reload_dstream(&mut bit_d);
+        }
+
+        *op.add(1) = fse_getsymbol!(&mut state2);
+
+        if RELOAD_4 {
+            /* This test must be static */
+            if fse_reload_dstream(&mut bit_d) > FSE_DSTREAM_UNFINISHED {
+                op = op.add(2);
+                break;
+            }
+        }
+
+        *op.add(2) = fse_getsymbol!(&mut state1);
+
+        if RELOAD_2 {
+            /* This test must be static */
+            fse_reload_dstream(&mut bit_d);
+        }
+
+        *op.add(3) = fse_getsymbol!(&mut state2);
+        op = op.add(4);
+    }
+
+    /* tail */
+    loop {
+        if fse_reload_dstream(&mut bit_d) > FSE_DSTREAM_COMPLETED
+            || (op as usize) == omax_addr
+            || (fse_end_of_dstream(&bit_d) && (fast || fse_end_of_dstate(&state1)))
+        {
+            break;
+        }
+
+        *op = fse_getsymbol!(&mut state1);
+        op = op.add(1);
+
+        if fse_reload_dstream(&mut bit_d) > FSE_DSTREAM_COMPLETED
+            || (op as usize) == omax_addr
+            || (fse_end_of_dstream(&bit_d) && (fast || fse_end_of_dstate(&state2)))
+        {
+            break;
+        }
+
+        *op = fse_getsymbol!(&mut state2);
+        op = op.add(1);
+    }
+
+    /* end ? */
+    if fse_end_of_dstream(&bit_d) && fse_end_of_dstate(&state1) && fse_end_of_dstate(&state2) {
+        return (op as usize) - (ostart as usize);
+    }
+
+    if (op as usize) == omax_addr {
+        /* dst buffer is full, but cSrc unfinished */
+        return fse_error(FSE_ERROR_DST_SIZE_TOO_SMALL);
+    }
+
+    fse_error(FSE_ERROR_CORRUPTION_DETECTED)
+}
+
+unsafe fn fse_decompress_using_dtable(
+    dst: *mut u8,
+    original_size: usize,
+    c_src: *const u8,
+    c_src_size: usize,
+    dt: *const u32,
+) -> usize {
+    let fast_mode = (*(dt as *const FseDTableHeader)).fast_mode;
+
+    /* select fast mode (static) */
+    if fast_mode != 0 {
+        return fse_decompress_using_dtable_generic(
+            dst,
+            original_size,
+            c_src,
+            c_src_size,
+            dt,
+            true,
+        );
+    }
+    fse_decompress_using_dtable_generic(dst, original_size, c_src, c_src_size, dt, false)
+}
+
+unsafe fn fse_decompress(
+    dst: *mut u8,
+    max_dst_size: usize,
+    c_src: *const u8,
+    c_src_size: usize,
+) -> usize {
+    let istart = c_src;
+    let mut ip = istart;
+    let mut counting = [0i16; (FSE_MAX_SYMBOL_VALUE + 1) as usize];
+    let mut dt = [0u32; 1 + (1 << FSE_MAX_TABLELOG)]; /* DTable_max_t */
+    let mut table_log: u32 = 0;
+    let mut max_symbol_value: u32 = FSE_MAX_SYMBOL_VALUE;
+    let mut remaining_size = c_src_size;
+
+    if c_src_size < 2 {
+        return fse_error(FSE_ERROR_SRC_SIZE_WRONG); /* too small input size */
+    }
+
+    /* normal FSE decoding mode */
+    let error_code = fse_read_ncount(
+        counting.as_mut_ptr(),
+        &mut max_symbol_value,
+        &mut table_log,
+        istart,
+        c_src_size,
+    );
+    if fse_is_error(error_code) {
+        return error_code;
+    }
+    if error_code >= c_src_size {
+        return fse_error(FSE_ERROR_SRC_SIZE_WRONG); /* too small input size */
+    }
+    ip = ip.add(error_code);
+    remaining_size -= error_code;
+
+    let error_code = fse_build_dtable(
+        dt.as_mut_ptr(),
+        counting.as_ptr(),
+        max_symbol_value,
+        table_log,
+    );
+    if fse_is_error(error_code) {
+        return error_code;
+    }
+
+    /* always return, even if it is an error code */
+    fse_decompress_using_dtable(dst, max_dst_size, ip, remaining_size, dt.as_ptr())
+}
+
+/* ******************************************
+ *  Huff0 : Huffman block decompression
+ ********************************************/
+#[repr(C)]
+#[derive(Clone, Copy)]
+struct HufDElt {
+    byte: u8,
+    nb_bits: u8,
+}
+
+/* Loop shapes and arithmetic below intentionally mirror the frozen C. */
+#[allow(clippy::needless_range_loop, clippy::manual_div_ceil)]
+unsafe fn huf_read_dtable(dtable: *mut u16, src: *const u8, src_size: usize) -> usize {
+    let mut huff_weight = [0u8; (HUF_MAX_SYMBOL_VALUE + 1) as usize];
+    let mut rank_val = [0u32; (HUF_ABSOLUTEMAX_TABLELOG + 1) as usize];
+    let ip = src;
+    let dt = dtable.add(1) as *mut HufDElt;
+
+    if src_size == 0 {
+        return fse_error(FSE_ERROR_SRC_SIZE_WRONG);
+    }
+    let mut i_size = *ip as usize;
+
+    let o_size: usize;
+    if i_size >= 128 {
+        /* special header */
+        if i_size >= 242 {
+            /* RLE */
+            const L: [usize; 14] = [1, 2, 3, 4, 7, 8, 15, 16, 31, 32, 63, 64, 127, 128];
+            o_size = L[i_size - 242];
+            huff_weight = [1u8; (HUF_MAX_SYMBOL_VALUE + 1) as usize];
+            i_size = 0;
+        } else {
+            /* Incompressible */
+            o_size = i_size - 127;
+            i_size = (o_size + 1) / 2;
+            if i_size + 1 > src_size {
+                return fse_error(FSE_ERROR_SRC_SIZE_WRONG);
+            }
+            let ip = ip.add(1);
+            let mut n = 0usize;
+            while n < o_size {
+                huff_weight[n] = *ip.add(n / 2) >> 4;
+                huff_weight[n + 1] = *ip.add(n / 2) & 15;
+                n += 2;
+            }
+        }
+    } else {
+        /* header compressed with FSE (normal case) */
+        if i_size + 1 > src_size {
+            return fse_error(FSE_ERROR_SRC_SIZE_WRONG);
+        }
+        /* max 255 values decoded, last one is implied */
+        let decoded = fse_decompress(
+            huff_weight.as_mut_ptr(),
+            HUF_MAX_SYMBOL_VALUE as usize,
+            ip.add(1),
+            i_size,
+        );
+        if fse_is_error(decoded) {
+            return decoded;
+        }
+        o_size = decoded;
+    }
+
+    /* collect weight stats */
+    let mut weight_total: u32 = 0;
+    for n in 0..o_size {
+        if huff_weight[n] >= HUF_ABSOLUTEMAX_TABLELOG as u8 {
+            return fse_error(FSE_ERROR_CORRUPTION_DETECTED);
+        }
+        rank_val[huff_weight[n] as usize] += 1;
+        weight_total += (1u32 << huff_weight[n]) >> 1;
+    }
+    if weight_total == 0 {
+        return fse_error(FSE_ERROR_CORRUPTION_DETECTED);
+    }
+
+    /* get last non-null symbol weight (implied, total must be 2^n) */
+    let max_bits = fse_highbit32(weight_total) + 1;
+    if max_bits > *dtable as u32 {
+        return fse_error(FSE_ERROR_TABLELOG_TOO_LARGE); /* DTable is too small */
+    }
+    *dtable = max_bits as u16;
+    {
+        let total = 1u32 << max_bits;
+        let rest = total - weight_total;
+        let verif = 1u32 << fse_highbit32(rest);
+        let last_weight = fse_highbit32(rest) + 1;
+        if verif != rest {
+            return fse_error(FSE_ERROR_CORRUPTION_DETECTED); /* last value must be a clean power of 2 */
+        }
+        huff_weight[o_size] = last_weight as u8;
+        rank_val[last_weight as usize] += 1;
+    }
+
+    /* check tree construction validity */
+    if rank_val[1] < 2 || (rank_val[1] & 1) != 0 {
+        /* by construction : at least 2 elts of rank 1, must be even */
+        return fse_error(FSE_ERROR_CORRUPTION_DETECTED);
+    }
+
+    /* Prepare ranks */
+    let mut next_rank_start: u32 = 0;
+    for n in 1..=(max_bits as usize) {
+        let current = next_rank_start;
+        next_rank_start += rank_val[n] << (n - 1);
+        rank_val[n] = current;
+    }
+
+    /* fill DTable */
+    for n in 0..=o_size {
+        let w = huff_weight[n] as usize;
+        let length = (1u32 << w) >> 1;
+        let d = HufDElt {
+            byte: n as u8,
+            nb_bits: (max_bits + 1 - w as u32) as u8,
+        };
+        for i in rank_val[w]..(rank_val[w] + length) {
+            *dt.add(i as usize) = d;
+        }
+        rank_val[w] += length;
+    }
+
+    i_size + 1
+}
+
+unsafe fn huf_decode_symbol(d_stream: &mut FseDStream, dt: *const HufDElt, dt_log: u32) -> u8 {
+    let val = fse_look_bits_fast(d_stream, dt_log); /* note : dtLog >= 1 */
+    let entry = *dt.add(val);
+    fse_skip_bits(d_stream, entry.nb_bits as u32);
+    entry.byte
+}
+
+/* The C decode macros: SYMBOL_1 reloads on 32-bit only when
+ * HUF_MAX_TABLELOG > 12 (never here); SYMBOL_2 reloads on 32-bit. */
+#[inline]
+unsafe fn huf_decode_symbol_1(
+    op: *mut u8,
+    d_stream: &mut FseDStream,
+    dt: *const HufDElt,
+    dt_log: u32,
+) {
+    *op = huf_decode_symbol(d_stream, dt, dt_log);
+    if IS_32BITS && HUF_MAX_TABLELOG > 12 {
+        fse_reload_dstream(d_stream);
+    }
+}
+
+#[inline]
+unsafe fn huf_decode_symbol_2(
+    op: *mut u8,
+    d_stream: &mut FseDStream,
+    dt: *const HufDElt,
+    dt_log: u32,
+) {
+    *op = huf_decode_symbol(d_stream, dt, dt_log);
+    if IS_32BITS {
+        fse_reload_dstream(d_stream);
+    }
+}
+
+unsafe fn huf_decompress_using_dtable(
+    dst: *mut u8,
+    max_dst_size: usize,
+    c_src: *const u8,
+    c_src_size: usize,
+    dtable: *const u16,
+) -> usize {
+    if c_src_size < 6 {
+        return fse_error(FSE_ERROR_SRC_SIZE_WRONG);
+    }
+
+    let ostart = dst;
+    let mut op = ostart;
+    let omax_addr = (op as usize).wrapping_add(max_dst_size);
+    let olimit_addr = if max_dst_size < 15 {
+        op as usize
+    } else {
+        omax_addr - 15
+    };
+
+    let dt = dtable.add(1) as *const HufDElt;
+    let dt_log = *dtable as u32;
+
+    /* Init */
+    let length1 = fse_read_le16(c_src) as usize;
+    let length2 = fse_read_le16(c_src.add(2)) as usize;
+    let length3 = fse_read_le16(c_src.add(4)) as usize;
+    let length4 = c_src_size
+        .wrapping_sub(6)
+        .wrapping_sub(length1)
+        .wrapping_sub(length2)
+        .wrapping_sub(length3); /* check coherency !! */
+    let start1 = c_src.add(6);
+    let start2 = start1.wrapping_add(length1);
+    let start3 = start2.wrapping_add(length2);
+    let start4 = start3.wrapping_add(length3);
+
+    if length1 + length2 + length3 + 6 >= c_src_size {
+        return fse_error(FSE_ERROR_SRC_SIZE_WRONG);
+    }
+
+    let mut bit_d1 = FseDStream {
+        bit_container: 0,
+        bits_consumed: 0,
+        ptr: ptr::null(),
+        start: ptr::null(),
+    };
+    let mut bit_d2 = FseDStream {
+        bit_container: 0,
+        bits_consumed: 0,
+        ptr: ptr::null(),
+        start: ptr::null(),
+    };
+    let mut bit_d3 = FseDStream {
+        bit_container: 0,
+        bits_consumed: 0,
+        ptr: ptr::null(),
+        start: ptr::null(),
+    };
+    let mut bit_d4 = FseDStream {
+        bit_container: 0,
+        bits_consumed: 0,
+        ptr: ptr::null(),
+        start: ptr::null(),
+    };
+
+    let error_code = fse_init_dstream(&mut bit_d1, start1, length1);
+    if fse_is_error(error_code) {
+        return error_code;
+    }
+    let error_code = fse_init_dstream(&mut bit_d2, start2, length2);
+    if fse_is_error(error_code) {
+        return error_code;
+    }
+    let error_code = fse_init_dstream(&mut bit_d3, start3, length3);
+    if fse_is_error(error_code) {
+        return error_code;
+    }
+    let error_code = fse_init_dstream(&mut bit_d4, start4, length4);
+    if fse_is_error(error_code) {
+        return error_code;
+    }
+
+    let mut reload_status = fse_reload_dstream(&mut bit_d2);
+
+    /* 16 symbols per loop; D2-3-4 are supposed to be synchronized and finish together */
+    while reload_status < FSE_DSTREAM_COMPLETED && (op as usize) < olimit_addr {
+        huf_decode_symbol_1(op, &mut bit_d1, dt, dt_log);
+        huf_decode_symbol_1(op.add(1), &mut bit_d2, dt, dt_log);
+        huf_decode_symbol_1(op.add(2), &mut bit_d3, dt, dt_log);
+        huf_decode_symbol_1(op.add(3), &mut bit_d4, dt, dt_log);
+        huf_decode_symbol_2(op.add(4), &mut bit_d1, dt, dt_log);
+        huf_decode_symbol_2(op.add(5), &mut bit_d2, dt, dt_log);
+        huf_decode_symbol_2(op.add(6), &mut bit_d3, dt, dt_log);
+        huf_decode_symbol_2(op.add(7), &mut bit_d4, dt, dt_log);
+        huf_decode_symbol_1(op.add(8), &mut bit_d1, dt, dt_log);
+        huf_decode_symbol_1(op.add(9), &mut bit_d2, dt, dt_log);
+        huf_decode_symbol_1(op.add(10), &mut bit_d3, dt, dt_log);
+        huf_decode_symbol_1(op.add(11), &mut bit_d4, dt, dt_log);
+        *op.add(12) = huf_decode_symbol(&mut bit_d1, dt, dt_log);
+        *op.add(13) = huf_decode_symbol(&mut bit_d2, dt, dt_log);
+        *op.add(14) = huf_decode_symbol(&mut bit_d3, dt, dt_log);
+        *op.add(15) = huf_decode_symbol(&mut bit_d4, dt, dt_log);
+
+        op = op.add(16);
+        reload_status = fse_reload_dstream(&mut bit_d2)
+            | fse_reload_dstream(&mut bit_d3)
+            | fse_reload_dstream(&mut bit_d4);
+        fse_reload_dstream(&mut bit_d1);
+    }
+
+    if reload_status != FSE_DSTREAM_COMPLETED {
+        /* not complete : some bitStream might be FSE_DStream_unfinished */
+        return fse_error(FSE_ERROR_CORRUPTION_DETECTED);
+    }
+
+    /* tail */
+    {
+        let mut bit_tail = FseDStream {
+            bit_container: bit_d1.bit_container, /* required in case of FSE_DStream_endOfBuffer */
+            bits_consumed: bit_d1.bits_consumed,
+            ptr: bit_d1.ptr,
+            start: start1,
+        };
+        while fse_reload_dstream(&mut bit_tail) < FSE_DSTREAM_COMPLETED && (op as usize) < omax_addr
+        {
+            *op = huf_decode_symbol(&mut bit_tail, dt, dt_log);
+            op = op.add(1);
+        }
+
+        if fse_end_of_dstream(&bit_tail) {
+            return (op as usize) - (ostart as usize);
+        }
+    }
+
+    if (op as usize) == omax_addr {
+        return fse_error(FSE_ERROR_DST_SIZE_TOO_SMALL); /* dst buffer is full, but cSrc unfinished */
+    }
+
+    fse_error(FSE_ERROR_CORRUPTION_DETECTED)
+}
+
+unsafe fn huf_decompress(
+    dst: *mut u8,
+    max_dst_size: usize,
+    c_src: *const u8,
+    c_src_size: usize,
+) -> usize {
+    /* HUF_CREATE_STATIC_DTABLE(DTable, HUF_MAX_TABLELOG) */
+    let mut dtable = [0u16; 1 + (1 << HUF_MAX_TABLELOG)];
+    dtable[0] = HUF_MAX_TABLELOG as u16;
+    let mut ip = c_src;
+
+    let error_code = huf_read_dtable(dtable.as_mut_ptr(), c_src, c_src_size);
+    if fse_is_error(error_code) {
+        return error_code;
+    }
+    if error_code >= c_src_size {
+        return fse_error(FSE_ERROR_SRC_SIZE_WRONG);
+    }
+    ip = ip.add(error_code);
+
+    huf_decompress_using_dtable(
+        dst,
+        max_dst_size,
+        ip,
+        c_src_size - error_code,
+        dtable.as_ptr(),
+    )
+}
+
+/* ******************************************
+ *  zstd v0.1 frame decoding
+ ********************************************/
+const ZSTD_MAGIC_NUMBER: u32 = 0xFD2FB51E; /* 3rd version : seqNb header */
+
+const KB: usize = 1 << 10;
+const BLOCKSIZE: usize = 128 * KB; /* define, for static allocation */
+
+const MINMATCH: usize = 4;
+const MLBITS: u32 = 7;
+const LLBITS: u32 = 6;
+const OFFBITS: u32 = 5;
+const MAX_ML: u32 = (1 << MLBITS) - 1;
+const MAX_LL: u32 = (1 << LLBITS) - 1;
+const MAX_OFF: u32 = (1 << OFFBITS) - 1;
+#[allow(dead_code)] /* part of the frozen v0.1 constant set; used only by the compressor */
+const LIT_FSE_LOG: u32 = 11;
+const ML_FSE_LOG: u32 = 10;
+const LL_FSE_LOG: u32 = 10;
+const OFF_FSE_LOG: u32 = 9;
+
+const ZSTD_CONTENTSIZE_ERROR: u64 = 0u64.wrapping_sub(2);
+
+const ZSTD_BLOCK_HEADER_SIZE: usize = 3;
+const ZSTD_FRAME_HEADER_SIZE: usize = 4;
+
+/* FSE_DTABLE_SIZE_U32(maxTableLog) == 1 + (1 << maxTableLog) */
+const LL_DTABLE_SIZE_U32: usize = 1 + (1 << LL_FSE_LOG as usize);
+const OFF_DTABLE_SIZE_U32: usize = 1 + (1 << OFF_FSE_LOG as usize);
+const ML_DTABLE_SIZE_U32: usize = 1 + (1 << ML_FSE_LOG as usize);
+
+#[inline]
+unsafe fn zstd_copy4(dst: *mut u8, src: *const u8) {
+    ptr::copy_nonoverlapping(src, dst, 4);
+}
+
+#[inline]
+unsafe fn zstd_copy8(dst: *mut u8, src: *const u8) {
+    ptr::copy_nonoverlapping(src, dst, 8);
+}
+
+unsafe fn zstd_wildcopy(dst: *mut u8, src: *const u8, length: isize) {
+    let mut ip = src;
+    let mut op = dst;
+    let oend_addr = (op as usize).wrapping_add(length as usize);
+    while (op as usize) < oend_addr {
+        zstd_copy8(op, ip);
+        op = op.add(8);
+        ip = ip.add(8);
+    }
+}
+
+#[inline]
+unsafe fn zstd_read_le16(mem_ptr: *const u8) -> u16 {
+    u16::from_le_bytes(ptr::read_unaligned(mem_ptr as *const [u8; 2]))
+}
+
+#[inline]
+unsafe fn zstd_read_le24(mem_ptr: *const u8) -> u32 {
+    zstd_read_le16(mem_ptr) as u32 + ((*mem_ptr.add(2) as u32) << 16)
+}
+
+#[inline]
+unsafe fn zstd_read_be32(mem_ptr: *const u8) -> u32 {
+    u32::from_be_bytes(ptr::read_unaligned(mem_ptr as *const [u8; 4]))
+}
+
+/* blockType_t */
+const BT_COMPRESSED: u32 = 0;
+const BT_RAW: u32 = 1;
+const BT_RLE: u32 = 2;
+const BT_END: u32 = 3;
+
+struct BlockProperties {
+    block_type: u32,
+    orig_size: u32,
+}
+
+/// The v0.1 streaming decompression context (`dctx_t` in C).  The struct is
+/// opaque to C: `zstd_v01.h` only forward-declares it, so the definition now
+/// lives here.
+#[repr(C)]
+pub struct ZSTDv01_Dctx {
+    ll_table: [u32; LL_DTABLE_SIZE_U32],
+    off_table: [u32; OFF_DTABLE_SIZE_U32],
+    ml_table: [u32; ML_DTABLE_SIZE_U32],
+    previous_dst_end: *const u8,
+    base: *const u8,
+    expected: usize,
+    b_type: u32,
+    phase: u32,
+}
+
+unsafe fn zstdv01_getc_block_size(
+    src: *const u8,
+    src_size: usize,
+    bp_ptr: &mut BlockProperties,
+) -> usize {
+    if src_size < 3 {
+        return ERROR(ZstdErrorCode::SrcSizeWrong);
+    }
+
+    let header_flags = *src;
+    let c_size =
+        (*src.add(2) as u32) + ((*src.add(1) as u32) << 8) + (((header_flags & 7) as u32) << 16);
+
+    bp_ptr.block_type = (header_flags >> 6) as u32;
+    bp_ptr.orig_size = if bp_ptr.block_type == BT_RLE {
+        c_size
+    } else {
+        0
+    };
+
+    if bp_ptr.block_type == BT_END {
+        return 0;
+    }
+    if bp_ptr.block_type == BT_RLE {
+        return 1;
+    }
+    c_size as usize
+}
+
+unsafe fn zstd_copy_uncompressed_block(
+    dst: *mut u8,
+    max_dst_size: usize,
+    src: *const u8,
+    src_size: usize,
+) -> usize {
+    if src_size > max_dst_size {
+        return ERROR(ZstdErrorCode::DstSizeTooSmall);
+    }
+    if src_size > 0 {
+        ptr::copy_nonoverlapping(src, dst, src_size);
+    }
+    src_size
+}
+
+unsafe fn zstd_decompress_literals(
+    dst: *mut u8,
+    max_dst_size: usize,
+    src: *const u8,
+    src_size: usize,
+) -> usize {
+    let oend = dst.add(max_dst_size);
+    let ip = src;
+
+    /* check : minimum 2, for litSize, +1, for content */
+    if src_size <= 3 {
+        return ERROR(ZstdErrorCode::CorruptionDetected);
+    }
+
+    let mut lit_size = (*ip.add(1) as usize) + ((*ip as usize) << 8);
+    lit_size += (((*ip.offset(-3) as usize) >> 3) & 7) << 16; /* mmmmh.... */
+
+    if lit_size > max_dst_size {
+        return ERROR(ZstdErrorCode::DstSizeTooSmall);
+    }
+    let op = oend.sub(lit_size);
+    let error_code = huf_decompress(op, lit_size, ip.add(2), src_size - 2);
+    if fse_is_error(error_code) {
+        return ERROR(ZstdErrorCode::Generic);
+    }
+    lit_size
+}
+
+unsafe fn zstdv01_decode_literals_block(
+    dst: *mut u8,
+    max_dst_size: usize,
+    lit_start: &mut *const u8,
+    lit_size: &mut usize,
+    src: *const u8,
+    src_size: usize,
+) -> usize {
+    let istart = src;
+    let mut ip = istart;
+    let ostart = dst;
+    let oend = ostart.add(max_dst_size);
+    let mut litbp = BlockProperties {
+        block_type: 0,
+        orig_size: 0,
+    };
+
+    let litc_size = zstdv01_getc_block_size(src, src_size, &mut litbp);
+    if ERR_isError(litc_size) {
+        return litc_size;
+    }
+    if litc_size > src_size - ZSTD_BLOCK_HEADER_SIZE {
+        return ERROR(ZstdErrorCode::SrcSizeWrong);
+    }
+    ip = ip.add(ZSTD_BLOCK_HEADER_SIZE);
+
+    match litbp.block_type {
+        BT_RAW => {
+            *lit_start = ip;
+            ip = ip.add(litc_size);
+            *lit_size = litc_size;
+        }
+        BT_RLE => {
+            let rle_size = litbp.orig_size as usize;
+            if rle_size > max_dst_size {
+                return ERROR(ZstdErrorCode::DstSizeTooSmall);
+            }
+            if src_size == 0 {
+                return ERROR(ZstdErrorCode::SrcSizeWrong);
+            }
+            if rle_size > 0 {
+                ptr::write_bytes(oend.sub(rle_size), *ip, rle_size);
+            }
+            *lit_start = oend.sub(rle_size);
+            *lit_size = rle_size;
+            ip = ip.add(1);
+        }
+        BT_COMPRESSED => {
+            let decoded_lit_size = zstd_decompress_literals(dst, max_dst_size, ip, litc_size);
+            if ERR_isError(decoded_lit_size) {
+                return decoded_lit_size;
+            }
+            *lit_start = oend.sub(decoded_lit_size);
+            *lit_size = decoded_lit_size;
+            ip = ip.add(litc_size);
+        }
+        _ => {
+            /* bt_end and impossible values */
+            return ERROR(ZstdErrorCode::Generic);
+        }
+    }
+
+    (ip as usize) - (istart as usize)
+}
+
+#[allow(clippy::too_many_arguments)]
+unsafe fn zstdv01_decode_seq_headers(
+    nb_seq: &mut i32,
+    dumps_ptr: &mut *const u8,
+    dumps_length_ptr: &mut usize,
+    dtable_ll: *mut u32,
+    dtable_ml: *mut u32,
+    dtable_offb: *mut u32,
+    src: *const u8,
+    src_size: usize,
+) -> usize {
+    let istart = src;
+    let mut ip = istart;
+    let iend_addr = (istart as usize).wrapping_add(src_size);
+
+    /* check */
+    if src_size < 5 {
+        return ERROR(ZstdErrorCode::SrcSizeWrong);
+    }
+
+    /* SeqHead */
+    *nb_seq = zstd_read_le16(ip) as i32;
+    ip = ip.add(2);
+    let ll_type = (*ip >> 6) as u32;
+    let off_type = ((*ip >> 4) & 3) as u32;
+    let ml_type = ((*ip >> 2) & 3) as u32;
+    let dumps_length: usize;
+    if (*ip & 2) != 0 {
+        dumps_length = (*ip.add(2) as usize) + ((*ip.add(1) as usize) << 8);
+        ip = ip.add(3);
+    } else {
+        dumps_length = (*ip.add(1) as usize) + (((*ip as usize) & 1) << 8);
+        ip = ip.add(2);
+    }
+    *dumps_ptr = ip;
+    ip = ip.wrapping_add(dumps_length);
+    *dumps_length_ptr = dumps_length;
+
+    /* check */
+    if (ip as usize) > iend_addr.wrapping_sub(3) {
+        /* min : all 3 are "raw", hence no header, but at least xxLog bits per type */
+        return ERROR(ZstdErrorCode::SrcSizeWrong);
+    }
+
+    /* sequences */
+    {
+        let mut norm = [0i16; (MAX_ML + 1) as usize]; /* assumption : MaxML >= MaxLL and MaxOff */
+
+        /* Build DTables */
+        match ll_type {
+            BT_RLE => {
+                fse_build_dtable_rle(dtable_ll, *ip);
+                ip = ip.add(1);
+            }
+            BT_RAW => {
+                fse_build_dtable_raw(dtable_ll, LLBITS);
+            }
+            _ => {
+                let mut max = MAX_LL;
+                let mut ll_log = 0u32;
+                let header_size = fse_read_ncount(
+                    norm.as_mut_ptr(),
+                    &mut max,
+                    &mut ll_log,
+                    ip,
+                    iend_addr - ip as usize,
+                );
+                if fse_is_error(header_size) {
+                    return ERROR(ZstdErrorCode::Generic);
+                }
+                if ll_log > LL_FSE_LOG {
+                    return ERROR(ZstdErrorCode::CorruptionDetected);
+                }
+                ip = ip.add(header_size);
+                fse_build_dtable(dtable_ll, norm.as_ptr(), max, ll_log);
+            }
+        }
+
+        match off_type {
+            BT_RLE => {
+                if (ip as usize) > iend_addr.wrapping_sub(2) {
+                    /* min : "raw", hence no header, but at least xxLog bits */
+                    return ERROR(ZstdErrorCode::SrcSizeWrong);
+                }
+                fse_build_dtable_rle(dtable_offb, *ip);
+                ip = ip.add(1);
+            }
+            BT_RAW => {
+                fse_build_dtable_raw(dtable_offb, OFFBITS);
+            }
+            _ => {
+                let mut max = MAX_OFF;
+                let mut off_log = 0u32;
+                let header_size = fse_read_ncount(
+                    norm.as_mut_ptr(),
+                    &mut max,
+                    &mut off_log,
+                    ip,
+                    iend_addr - ip as usize,
+                );
+                if fse_is_error(header_size) {
+                    return ERROR(ZstdErrorCode::Generic);
+                }
+                if off_log > OFF_FSE_LOG {
+                    return ERROR(ZstdErrorCode::CorruptionDetected);
+                }
+                ip = ip.add(header_size);
+                fse_build_dtable(dtable_offb, norm.as_ptr(), max, off_log);
+            }
+        }
+
+        match ml_type {
+            BT_RLE => {
+                if (ip as usize) > iend_addr.wrapping_sub(2) {
+                    /* min : "raw", hence no header, but at least xxLog bits */
+                    return ERROR(ZstdErrorCode::SrcSizeWrong);
+                }
+                fse_build_dtable_rle(dtable_ml, *ip);
+                ip = ip.add(1);
+            }
+            BT_RAW => {
+                fse_build_dtable_raw(dtable_ml, MLBITS);
+            }
+            _ => {
+                let mut max = MAX_ML;
+                let mut ml_log = 0u32;
+                let header_size = fse_read_ncount(
+                    norm.as_mut_ptr(),
+                    &mut max,
+                    &mut ml_log,
+                    ip,
+                    iend_addr - ip as usize,
+                );
+                if fse_is_error(header_size) {
+                    return ERROR(ZstdErrorCode::Generic);
+                }
+                if ml_log > ML_FSE_LOG {
+                    return ERROR(ZstdErrorCode::CorruptionDetected);
+                }
+                ip = ip.add(header_size);
+                fse_build_dtable(dtable_ml, norm.as_ptr(), max, ml_log);
+            }
+        }
+    }
+
+    (ip as usize) - (istart as usize)
+}
+
+#[derive(Clone, Copy)]
+struct Seq {
+    lit_length: usize,
+    offset: usize,
+    match_length: usize,
+}
+
+struct SeqState {
+    d_stream: FseDStream,
+    state_ll: FseDState,
+    state_offb: FseDState,
+    state_ml: FseDState,
+    prev_offset: usize,
+    dumps: *const u8,
+    dumps_end: *const u8,
+}
+
+unsafe fn zstd_decode_sequence(seq: &mut Seq, seq_state: &mut SeqState) {
+    let mut dumps = seq_state.dumps;
+    let de = seq_state.dumps_end;
+
+    /* Literal length */
+    let mut lit_length =
+        fse_decode_symbol(&mut seq_state.state_ll, &mut seq_state.d_stream) as usize;
+    let prev_offset = if lit_length != 0 {
+        seq.offset
+    } else {
+        seq_state.prev_offset
+    };
+    seq_state.prev_offset = seq.offset;
+    if lit_length == MAX_LL as usize {
+        let add = if (dumps as usize) < (de as usize) {
+            let v = *dumps as u32;
+            dumps = dumps.add(1);
+            v
+        } else {
+            0
+        };
+        if add < 255 {
+            lit_length += add as usize;
+        } else if (dumps as usize) <= (de as usize).wrapping_sub(3) {
+            lit_length = zstd_read_le24(dumps) as usize;
+            dumps = dumps.add(3);
+        }
+    }
+
+    /* Offset */
+    let mut offset: usize;
+    {
+        let offset_code =
+            fse_decode_symbol(&mut seq_state.state_offb, &mut seq_state.d_stream) as u32;
+        if IS_32BITS {
+            fse_reload_dstream(&mut seq_state.d_stream);
+        }
+        let mut nb_bits = offset_code.wrapping_sub(1);
+        if offset_code == 0 {
+            nb_bits = 0; /* cmove */
+        }
+        offset = (1usize << (nb_bits & (USIZE_BITS - 1)))
+            .wrapping_add(fse_read_bits(&mut seq_state.d_stream, nb_bits));
+        if IS_32BITS {
+            fse_reload_dstream(&mut seq_state.d_stream);
+        }
+        if offset_code == 0 {
+            offset = prev_offset;
+        }
+    }
+
+    /* MatchLength */
+    let mut match_length =
+        fse_decode_symbol(&mut seq_state.state_ml, &mut seq_state.d_stream) as usize;
+    if match_length == MAX_ML as usize {
+        let add = if (dumps as usize) < (de as usize) {
+            let v = *dumps as u32;
+            dumps = dumps.add(1);
+            v
+        } else {
+            0
+        };
+        if add < 255 {
+            match_length += add as usize;
+        } else if (dumps as usize) <= (de as usize).wrapping_sub(3) {
+            match_length = zstd_read_le24(dumps) as usize;
+            dumps = dumps.add(3);
+        }
+    }
+    match_length += MINMATCH;
+
+    /* save result */
+    seq.lit_length = lit_length;
+    seq.offset = offset;
+    seq.match_length = match_length;
+    seq_state.dumps = dumps;
+}
+
+unsafe fn zstd_exec_sequence(
+    op: *mut u8,
+    sequence: Seq,
+    lit_ptr: &mut *const u8,
+    lit_limit: *const u8,
+    base: *const u8,
+    oend: *mut u8,
+) -> usize {
+    static DEC32TABLE: [usize; 8] = [0, 1, 2, 1, 4, 4, 4, 4]; /* added */
+    static DEC64TABLE: [usize; 8] = [8, 8, 8, 7, 8, 9, 10, 11]; /* subtracted */
+    let ostart = op;
+    let mut op = op;
+    let o_lit_end = op.wrapping_add(sequence.lit_length);
+    let lit_length = sequence.lit_length;
+    /* risk : address space overflow (32-bits) */
+    let end_match = op
+        .wrapping_add(lit_length)
+        .wrapping_add(sequence.match_length);
+    let lit_end = (*lit_ptr).wrapping_add(lit_length);
+
+    /* checks */
+    let seq_length = sequence.lit_length.wrapping_add(sequence.match_length);
+
+    if seq_length > (oend as usize).wrapping_sub(op as usize) {
+        return ERROR(ZstdErrorCode::DstSizeTooSmall);
+    }
+    if sequence.lit_length > (lit_limit as usize).wrapping_sub(*lit_ptr as usize) {
+        return ERROR(ZstdErrorCode::CorruptionDetected);
+    }
+    /* Now we know there are no overflow in literal nor match lengths, can use pointer checks */
+    if sequence.offset > ((o_lit_end as usize).wrapping_sub(base as usize)) as u32 as usize {
+        return ERROR(ZstdErrorCode::CorruptionDetected);
+    }
+
+    if (end_match as usize) > (oend as usize) {
+        /* overwrite beyond dst buffer */
+        return ERROR(ZstdErrorCode::DstSizeTooSmall);
+    }
+    if (lit_end as usize) > (lit_limit as usize) {
+        /* overRead beyond lit buffer */
+        return ERROR(ZstdErrorCode::CorruptionDetected);
+    }
+    if sequence.match_length > (*lit_ptr as usize).wrapping_sub(op as usize) {
+        /* overwrite literal segment */
+        return ERROR(ZstdErrorCode::DstSizeTooSmall);
+    }
+
+    /* copy Literals */
+    /* note : v0.1 seems to allow scenarios where output or input are close to end of buffer */
+    ptr::copy(*lit_ptr, op, sequence.lit_length);
+
+    op = op.add(lit_length);
+    *lit_ptr = lit_end; /* update for next sequence */
+
+    /* check : last match must be at a minimum distance of 8 from end of dest buffer */
+    if (oend as usize) - (op as usize) < 8 {
+        return ERROR(ZstdErrorCode::DstSizeTooSmall);
+    }
+
+    /* copy Match */
+    {
+        let overlap_risk = (lit_end as usize).wrapping_sub(end_match as usize) < 12;
+        /* possible underflow at op - offset ? */
+        let mut match_ptr = (op as usize).wrapping_sub(sequence.offset) as *const u8;
+        let mut qutt: usize = 12;
+        let mut saved = [0u8; 16]; /* U64 saved[2] */
+
+        /* check */
+        if (match_ptr as usize) < (base as usize) {
+            return ERROR(ZstdErrorCode::CorruptionDetected);
+        }
+        if sequence.offset > base as usize {
+            return ERROR(ZstdErrorCode::CorruptionDetected);
+        }
+
+        /* save beginning of literal sequence, in case of write overlap */
+        if overlap_risk {
+            if (end_match as usize).wrapping_add(qutt) > (oend as usize) {
+                qutt = (oend as usize) - (end_match as usize);
+            }
+            ptr::copy_nonoverlapping(end_match as *const u8, saved.as_mut_ptr(), qutt);
+        }
+
+        if sequence.offset < 8 {
+            let dec64 = DEC64TABLE[sequence.offset];
+            *op = *match_ptr;
+            *op.add(1) = *match_ptr.add(1);
+            *op.add(2) = *match_ptr.add(2);
+            *op.add(3) = *match_ptr.add(3);
+            match_ptr = match_ptr.add(DEC32TABLE[sequence.offset]);
+            zstd_copy4(op.add(4), match_ptr);
+            match_ptr = match_ptr.sub(dec64);
+        } else {
+            zstd_copy8(op, match_ptr);
+        }
+        op = op.add(8);
+        match_ptr = match_ptr.add(8);
+
+        if (end_match as usize) > (oend as usize).wrapping_sub(16 - MINMATCH) {
+            if (op as usize) < (oend as usize).wrapping_sub(8) {
+                let dist = ((oend as usize) - 8) - (op as usize);
+                zstd_wildcopy(op, match_ptr, dist as isize);
+                match_ptr = match_ptr.add(dist);
+                op = oend.sub(8);
+            }
+            while (op as usize) < (end_match as usize) {
+                *op = *match_ptr;
+                op = op.add(1);
+                match_ptr = match_ptr.add(1);
+            }
+        } else {
+            /* works even if matchLength < 8 */
+            zstd_wildcopy(op, match_ptr, sequence.match_length as isize - 8);
+        }
+
+        /* restore, in case of overlap */
+        if overlap_risk {
+            ptr::copy_nonoverlapping(saved.as_ptr(), end_match, qutt);
+        }
+    }
+
+    (end_match as usize) - (ostart as usize)
+}
+
+unsafe fn zstd_decompress_sequences(
+    ctx: *mut ZSTDv01_Dctx,
+    dst: *mut u8,
+    max_dst_size: usize,
+    seq_start: *const u8,
+    seq_size: usize,
+    lit_start: *const u8,
+    lit_size: usize,
+) -> usize {
+    let dctx = ctx;
+    let mut ip = seq_start;
+    let iend_addr = (ip as usize).wrapping_add(seq_size);
+    let ostart = dst;
+    let mut op = ostart;
+    let oend = ostart.add(max_dst_size);
+    let mut lit_ptr = lit_start;
+    let lit_end = lit_start.add(lit_size);
+    let mut nb_seq: i32 = 0;
+    let mut dumps: *const u8 = ptr::null();
+    let mut dumps_length: usize = 0;
+    let dtable_ll = (*dctx).ll_table.as_mut_ptr();
+    let dtable_ml = (*dctx).ml_table.as_mut_ptr();
+    let dtable_offb = (*dctx).off_table.as_mut_ptr();
+    let base = (*dctx).base;
+
+    /* Build Decoding Tables */
+    let error_code = zstdv01_decode_seq_headers(
+        &mut nb_seq,
+        &mut dumps,
+        &mut dumps_length,
+        dtable_ll,
+        dtable_ml,
+        dtable_offb,
+        ip,
+        iend_addr - ip as usize,
+    );
+    if ERR_isError(error_code) {
+        return error_code;
+    }
+    ip = ip.add(error_code);
+
+    /* Regen sequences */
+    {
+        let mut sequence = Seq {
+            lit_length: 0,
+            offset: 0,
+            match_length: 0,
+        };
+        let mut seq_state = SeqState {
+            d_stream: FseDStream {
+                bit_container: 0,
+                bits_consumed: 0,
+                ptr: ptr::null(),
+                start: ptr::null(),
+            },
+            state_ll: FseDState {
+                state: 0,
+                table: ptr::null(),
+            },
+            state_offb: FseDState {
+                state: 0,
+                table: ptr::null(),
+            },
+            state_ml: FseDState {
+                state: 0,
+                table: ptr::null(),
+            },
+            prev_offset: 1,
+            dumps,
+            dumps_end: dumps.wrapping_add(dumps_length),
+        };
+        let error_code = fse_init_dstream(&mut seq_state.d_stream, ip, iend_addr - ip as usize);
+        if fse_is_error(error_code) {
+            return ERROR(ZstdErrorCode::CorruptionDetected);
+        }
+        fse_init_dstate(&mut seq_state.state_ll, &mut seq_state.d_stream, dtable_ll);
+        fse_init_dstate(
+            &mut seq_state.state_offb,
+            &mut seq_state.d_stream,
+            dtable_offb,
+        );
+        fse_init_dstate(&mut seq_state.state_ml, &mut seq_state.d_stream, dtable_ml);
+
+        while fse_reload_dstream(&mut seq_state.d_stream) <= FSE_DSTREAM_COMPLETED && nb_seq > 0 {
+            nb_seq -= 1;
+            zstd_decode_sequence(&mut sequence, &mut seq_state);
+            let one_seq_size = zstd_exec_sequence(op, sequence, &mut lit_ptr, lit_end, base, oend);
+            if ERR_isError(one_seq_size) {
+                return one_seq_size;
+            }
+            op = op.add(one_seq_size);
+        }
+
+        /* check if reached exact end */
+        if !fse_end_of_dstream(&seq_state.d_stream) {
+            /* requested too much : data is corrupted */
+            return ERROR(ZstdErrorCode::CorruptionDetected);
+        }
+        if nb_seq < 0 {
+            /* requested too many sequences : data is corrupted */
+            return ERROR(ZstdErrorCode::CorruptionDetected);
+        }
+
+        /* last literal segment */
+        {
+            let last_ll_size = (lit_end as usize) - (lit_ptr as usize);
+            if (op as usize).wrapping_add(last_ll_size) > (oend as usize) {
+                return ERROR(ZstdErrorCode::DstSizeTooSmall);
+            }
+            if last_ll_size > 0 {
+                if !std::ptr::eq(op as *const u8, lit_ptr) {
+                    ptr::copy(lit_ptr, op, last_ll_size);
+                }
+                op = op.add(last_ll_size);
+            }
+        }
+    }
+
+    (op as usize) - (ostart as usize)
+}
+
+unsafe fn zstd_decompress_block(
+    ctx: *mut ZSTDv01_Dctx,
+    dst: *mut u8,
+    max_dst_size: usize,
+    src: *const u8,
+    src_size: usize,
+) -> usize {
+    /* blockType == blockCompressed, srcSize is trusted */
+    let mut ip = src;
+    let mut lit_ptr: *const u8 = ptr::null();
+    let mut lit_size: usize = 0;
+
+    /* Decode literals sub-block */
+    let error_code = zstdv01_decode_literals_block(
+        dst,
+        max_dst_size,
+        &mut lit_ptr,
+        &mut lit_size,
+        src,
+        src_size,
+    );
+    if ERR_isError(error_code) {
+        return error_code;
+    }
+    ip = ip.add(error_code);
+    let src_size = src_size - error_code;
+
+    zstd_decompress_sequences(ctx, dst, max_dst_size, ip, src_size, lit_ptr, lit_size)
+}
+
+unsafe fn zstdv01_decompress_dctx(
+    ctx: *mut ZSTDv01_Dctx,
+    dst: *mut u8,
+    max_dst_size: usize,
+    src: *const u8,
+    src_size: usize,
+) -> usize {
+    let mut ip = src;
+    let iend_addr = (ip as usize).wrapping_add(src_size);
+    let ostart = dst;
+    let mut op = ostart;
+    let oend_addr = (ostart as usize).wrapping_add(max_dst_size);
+    let mut remaining_size = src_size;
+    let mut error_code: usize = 0;
+
+    /* Frame Header */
+    if src_size < ZSTD_FRAME_HEADER_SIZE + ZSTD_BLOCK_HEADER_SIZE {
+        return ERROR(ZstdErrorCode::SrcSizeWrong);
+    }
+    let magic_number = zstd_read_be32(src);
+    if magic_number != ZSTD_MAGIC_NUMBER {
+        return ERROR(ZstdErrorCode::PrefixUnknown);
+    }
+    ip = ip.add(ZSTD_FRAME_HEADER_SIZE);
+    remaining_size -= ZSTD_FRAME_HEADER_SIZE;
+
+    /* Loop on each block */
+    loop {
+        let mut block_properties = BlockProperties {
+            block_type: 0,
+            orig_size: 0,
+        };
+        let block_size =
+            zstdv01_getc_block_size(ip, iend_addr - ip as usize, &mut block_properties);
+        if ERR_isError(block_size) {
+            return block_size;
+        }
+
+        ip = ip.add(ZSTD_BLOCK_HEADER_SIZE);
+        remaining_size -= ZSTD_BLOCK_HEADER_SIZE;
+        if block_size > remaining_size {
+            return ERROR(ZstdErrorCode::SrcSizeWrong);
+        }
+
+        match block_properties.block_type {
+            BT_COMPRESSED => {
+                error_code =
+                    zstd_decompress_block(ctx, op, oend_addr - op as usize, ip, block_size);
+            }
+            BT_RAW => {
+                error_code =
+                    zstd_copy_uncompressed_block(op, oend_addr - op as usize, ip, block_size);
+            }
+            BT_RLE => {
+                return ERROR(ZstdErrorCode::Generic); /* not yet supported */
+            }
+            BT_END => {
+                /* end of frame */
+                if remaining_size != 0 {
+                    return ERROR(ZstdErrorCode::SrcSizeWrong);
+                }
+            }
+            _ => {
+                return ERROR(ZstdErrorCode::Generic);
+            }
+        }
+        if block_size == 0 {
+            break; /* bt_end */
+        }
+
+        if ERR_isError(error_code) {
+            return error_code;
+        }
+        op = op.add(error_code);
+        ip = ip.add(block_size);
+        remaining_size -= block_size;
+    }
+
+    (op as usize) - (ostart as usize)
+}
+
+/* ZSTD_errorFrameSizeInfoLegacy() :
+assumes `cSize` and `dBound` are _not_ NULL */
+unsafe fn zstd_error_frame_size_info_legacy(c_size: *mut usize, d_bound: *mut u64, ret: usize) {
+    *c_size = ret;
+    *d_bound = ZSTD_CONTENTSIZE_ERROR;
+}
+
+/* ******************************************
+ *  Exported C ABI (zstd_v01.h)
+ ********************************************/
+
+/// C ABI: `ZSTDv01_isError`.
+#[no_mangle]
+pub extern "C" fn ZSTDv01_isError(code: usize) -> c_uint {
+    ERR_isError(code) as c_uint
+}
+
+/// C ABI: `ZSTDv01_decompressDCtx`.
+#[no_mangle]
+pub unsafe extern "C" fn ZSTDv01_decompressDCtx(
+    ctx: *mut c_void,
+    dst: *mut c_void,
+    max_original_size: usize,
+    src: *const c_void,
+    compressed_size: usize,
+) -> usize {
+    zstdv01_decompress_dctx(
+        ctx as *mut ZSTDv01_Dctx,
+        dst as *mut u8,
+        max_original_size,
+        src as *const u8,
+        compressed_size,
+    )
+}
+
+/// C ABI: `ZSTDv01_decompress`.
+#[no_mangle]
+pub unsafe extern "C" fn ZSTDv01_decompress(
+    dst: *mut c_void,
+    max_original_size: usize,
+    src: *const c_void,
+    compressed_size: usize,
+) -> usize {
+    /* The C version uses an uninitialized on-stack dctx_t; only `base` is
+     * read before being written, so a zeroed context is equivalent. */
+    let mut ctx = std::mem::MaybeUninit::<ZSTDv01_Dctx>::zeroed();
+    let ctx_ptr = ctx.as_mut_ptr();
+    (*ctx_ptr).base = dst as *const u8;
+    zstdv01_decompress_dctx(
+        ctx_ptr,
+        dst as *mut u8,
+        max_original_size,
+        src as *const u8,
+        compressed_size,
+    )
+}
+
+/// C ABI: `ZSTDv01_findFrameSizeInfoLegacy`.
+#[no_mangle]
+pub unsafe extern "C" fn ZSTDv01_findFrameSizeInfoLegacy(
+    src: *const c_void,
+    src_size: usize,
+    c_size: *mut usize,
+    d_bound: *mut u64,
+) {
+    let mut ip = src as *const u8;
+    let mut remaining_size = src_size;
+    let mut nb_blocks: usize = 0;
+
+    /* Frame Header */
+    if src_size < ZSTD_FRAME_HEADER_SIZE + ZSTD_BLOCK_HEADER_SIZE {
+        zstd_error_frame_size_info_legacy(c_size, d_bound, ERROR(ZstdErrorCode::SrcSizeWrong));
+        return;
+    }
+    let magic_number = zstd_read_be32(src as *const u8);
+    if magic_number != ZSTD_MAGIC_NUMBER {
+        zstd_error_frame_size_info_legacy(c_size, d_bound, ERROR(ZstdErrorCode::PrefixUnknown));
+        return;
+    }
+    ip = ip.add(ZSTD_FRAME_HEADER_SIZE);
+    remaining_size -= ZSTD_FRAME_HEADER_SIZE;
+
+    /* Loop on each block */
+    loop {
+        let mut block_properties = BlockProperties {
+            block_type: 0,
+            orig_size: 0,
+        };
+        let block_size = zstdv01_getc_block_size(ip, remaining_size, &mut block_properties);
+        if ERR_isError(block_size) {
+            zstd_error_frame_size_info_legacy(c_size, d_bound, block_size);
+            return;
+        }
+
+        ip = ip.add(ZSTD_BLOCK_HEADER_SIZE);
+        remaining_size -= ZSTD_BLOCK_HEADER_SIZE;
+        if block_size > remaining_size {
+            zstd_error_frame_size_info_legacy(c_size, d_bound, ERROR(ZstdErrorCode::SrcSizeWrong));
+            return;
+        }
+
+        if block_size == 0 {
+            break; /* bt_end */
+        }
+
+        ip = ip.add(block_size);
+        remaining_size -= block_size;
+        nb_blocks += 1;
+    }
+
+    *c_size = (ip as usize) - (src as usize);
+    *d_bound = (nb_blocks * BLOCKSIZE) as u64;
+}
+
+/* ******************************************
+ *  Streaming Decompression API
+ ********************************************/
+
+/// C ABI: `ZSTDv01_resetDCtx`.
+#[no_mangle]
+pub unsafe extern "C" fn ZSTDv01_resetDCtx(dctx: *mut ZSTDv01_Dctx) -> usize {
+    (*dctx).expected = ZSTD_FRAME_HEADER_SIZE;
+    (*dctx).phase = 0;
+    (*dctx).previous_dst_end = ptr::null();
+    (*dctx).base = ptr::null();
+    0
+}
+
+/// C ABI: `ZSTDv01_createDCtx`.  Allocated with `malloc` exactly like the C
+/// implementation, so create/free may be paired across the C/Rust boundary.
+#[no_mangle]
+pub unsafe extern "C" fn ZSTDv01_createDCtx() -> *mut ZSTDv01_Dctx {
+    let dctx = libc::malloc(std::mem::size_of::<ZSTDv01_Dctx>()) as *mut ZSTDv01_Dctx;
+    if dctx.is_null() {
+        return ptr::null_mut();
+    }
+    ZSTDv01_resetDCtx(dctx);
+    dctx
+}
+
+/// C ABI: `ZSTDv01_freeDCtx`.
+#[no_mangle]
+pub unsafe extern "C" fn ZSTDv01_freeDCtx(dctx: *mut ZSTDv01_Dctx) -> usize {
+    libc::free(dctx as *mut c_void);
+    0
+}
+
+/// C ABI: `ZSTDv01_nextSrcSizeToDecompress`.
+#[no_mangle]
+pub unsafe extern "C" fn ZSTDv01_nextSrcSizeToDecompress(dctx: *mut ZSTDv01_Dctx) -> usize {
+    (*dctx).expected
+}
+
+/// C ABI: `ZSTDv01_decompressContinue`.
+#[no_mangle]
+pub unsafe extern "C" fn ZSTDv01_decompressContinue(
+    dctx: *mut ZSTDv01_Dctx,
+    dst: *mut c_void,
+    max_dst_size: usize,
+    src: *const c_void,
+    src_size: usize,
+) -> usize {
+    let ctx = dctx;
+    let src = src as *const u8;
+    let dst = dst as *mut u8;
+
+    /* Sanity check */
+    if src_size != (*ctx).expected {
+        return ERROR(ZstdErrorCode::SrcSizeWrong);
+    }
+    if !std::ptr::eq(dst as *const u8, (*ctx).previous_dst_end) {
+        /* not contiguous */
+        (*ctx).base = dst as *const u8;
+    }
+
+    /* Decompress : frame header */
+    if (*ctx).phase == 0 {
+        /* Check frame magic header */
+        let magic_number = zstd_read_be32(src);
+        if magic_number != ZSTD_MAGIC_NUMBER {
+            return ERROR(ZstdErrorCode::PrefixUnknown);
+        }
+        (*ctx).phase = 1;
+        (*ctx).expected = ZSTD_BLOCK_HEADER_SIZE;
+        return 0;
+    }
+
+    /* Decompress : block header */
+    if (*ctx).phase == 1 {
+        let mut bp = BlockProperties {
+            block_type: 0,
+            orig_size: 0,
+        };
+        let block_size = zstdv01_getc_block_size(src, ZSTD_BLOCK_HEADER_SIZE, &mut bp);
+        if ERR_isError(block_size) {
+            return block_size;
+        }
+        if bp.block_type == BT_END {
+            (*ctx).expected = 0;
+            (*ctx).phase = 0;
+        } else {
+            (*ctx).expected = block_size;
+            (*ctx).b_type = bp.block_type;
+            (*ctx).phase = 2;
+        }
+
+        return 0;
+    }
+
+    /* Decompress : block content */
+    {
+        let r_size = match (*ctx).b_type {
+            BT_COMPRESSED => zstd_decompress_block(ctx, dst, max_dst_size, src, src_size),
+            BT_RAW => zstd_copy_uncompressed_block(dst, max_dst_size, src, src_size),
+            BT_RLE => {
+                return ERROR(ZstdErrorCode::Generic); /* not yet handled */
+            }
+            BT_END => {
+                /* should never happen (filtered at phase 1) */
+                0
+            }
+            _ => {
+                return ERROR(ZstdErrorCode::Generic);
+            }
+        };
+        (*ctx).phase = 1;
+        (*ctx).expected = ZSTD_BLOCK_HEADER_SIZE;
+        if ERR_isError(r_size) {
+            return r_size;
+        }
+        (*ctx).previous_dst_end = (dst as usize + r_size) as *const u8;
+        r_size
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// 237-byte base text; the fixtures compress repetitions of it.
+    const SAMPLE: &str = "snowden is snowed in / he's now then in his snow den / when does the snow end?\ngoodbye little dog / you dug some holes in your day / they'll be hard to fill.\nwhen life shuts a door, / just open it. it's a door. / that is how doors work.\n";
+
+    /// `SAMPLE` repeated 3 times (711 bytes), compressed by a zstd binary
+    /// built from the v0.1.0 tag.  Single compressed block (FSE + Huff0),
+    /// verified byte-identical against the pristine C decoder.
+    const FRAME_ENTROPY: &[u8] = &[
+        0xFD, 0x2F, 0xB5, 0x1E, 0x00, 0x00, 0xB0, 0x00, 0x00, 0x93, 0x00, 0xD6, 0x19, 0x80, 0x87,
+        0xB1, 0x00, 0xC0, 0x73, 0xC5, 0x8A, 0xA5, 0x6C, 0x6F, 0x4B, 0xF2, 0x9F, 0x94, 0xC4, 0x2B,
+        0xE4, 0x6B, 0x2C, 0x96, 0xAE, 0x5F, 0xC8, 0x9C, 0x1F, 0x00, 0x1C, 0x00, 0x1B, 0x00, 0x43,
+        0x31, 0x70, 0xE4, 0xC9, 0xA3, 0x46, 0xD9, 0xAD, 0xFD, 0x78, 0x37, 0x66, 0xA6, 0x4D, 0x15,
+        0xCA, 0x33, 0xF5, 0xA7, 0x31, 0x83, 0x02, 0x96, 0x7E, 0xD0, 0x5E, 0xAC, 0xE9, 0x48, 0x03,
+        0xC7, 0xEF, 0x44, 0x81, 0x0B, 0x00, 0x90, 0xEA, 0x55, 0x41, 0xD8, 0x4E, 0x36, 0x10, 0xAC,
+        0x95, 0x92, 0x42, 0x5D, 0x92, 0xF4, 0x64, 0x7F, 0x96, 0x44, 0x59, 0x0B, 0x03, 0x4A, 0xF6,
+        0x16, 0x9F, 0xC8, 0xB9, 0x11, 0x70, 0xB8, 0x35, 0x06, 0xC4, 0x26, 0xC7, 0x6A, 0x89, 0xE4,
+        0x6F, 0x65, 0xC0, 0x9B, 0x55, 0x08, 0xEB, 0xE8, 0x37, 0x66, 0x67, 0x9E, 0x7D, 0x57, 0xA0,
+        0x25, 0x0D, 0xA4, 0x3E, 0x26, 0x8F, 0x32, 0xF6, 0xC9, 0x49, 0x50, 0x40, 0x0A, 0xED, 0x34,
+        0x94, 0x15, 0x5E, 0xE3, 0x1B, 0xD6, 0x27, 0x05, 0x00, 0x54, 0x05, 0x41, 0xFF, 0xD6, 0x01,
+        0x00, 0x80, 0x36, 0x00, 0xFE, 0x8D, 0x38, 0x42, 0x51, 0x7E, 0x40, 0x38, 0xD5, 0x60, 0x46,
+        0x03, 0x90, 0x25, 0xC0, 0x00, 0x00,
+    ];
+
+    /// 48 random bytes compressed by v0.1.0: a raw (uncompressed) block.
+    const FRAME_RAW: &[u8] = &[
+        0xFD, 0x2F, 0xB5, 0x1E, 0x40, 0x00, 0x30, 0x77, 0xE9, 0x9A, 0x70, 0x2F, 0x77, 0x16, 0x9A,
+        0x92, 0xD4, 0xEE, 0x72, 0xFD, 0xDD, 0x0F, 0x39, 0x33, 0x8B, 0x8B, 0x3C, 0x6A, 0x91, 0xB2,
+        0x2B, 0x3A, 0xF0, 0x0E, 0xA6, 0x4C, 0x51, 0xA0, 0xC9, 0x5F, 0x69, 0x1A, 0xCE, 0x93, 0x5C,
+        0x7F, 0x43, 0x0C, 0xD9, 0x25, 0xBC, 0x91, 0xDD, 0x6E, 0xD7, 0xC0, 0x00, 0x00,
+    ];
+
+    const RAW_PAYLOAD: &[u8] = &[
+        0x77, 0xE9, 0x9A, 0x70, 0x2F, 0x77, 0x16, 0x9A, 0x92, 0xD4, 0xEE, 0x72, 0xFD, 0xDD, 0x0F,
+        0x39, 0x33, 0x8B, 0x8B, 0x3C, 0x6A, 0x91, 0xB2, 0x2B, 0x3A, 0xF0, 0x0E, 0xA6, 0x4C, 0x51,
+        0xA0, 0xC9, 0x5F, 0x69, 0x1A, 0xCE, 0x93, 0x5C, 0x7F, 0x43, 0x0C, 0xD9, 0x25, 0xBC, 0x91,
+        0xDD, 0x6E, 0xD7,
+    ];
+
+    /// `SAMPLE` repeated 1800 times (426600 bytes) compressed by v0.1.0:
+    /// four data blocks, so it exercises multi-block frames and repeated
+    /// offsets.
+    const FRAME_MULTI_BLOCK: &[u8] = &[
+        0xFD, 0x2F, 0xB5, 0x1E, 0x00, 0x00, 0xB0, 0x00, 0x00, 0x93, 0x00, 0xD6, 0x19, 0x80, 0x87,
+        0xB1, 0x00, 0xC0, 0x73, 0xC5, 0x8A, 0xA5, 0x6C, 0x6F, 0x4B, 0xF2, 0x9F, 0x94, 0xC4, 0x2B,
+        0xE4, 0x6B, 0x2C, 0x96, 0xAE, 0x5F, 0xC8, 0x9C, 0x1F, 0x00, 0x1C, 0x00, 0x1B, 0x00, 0x43,
+        0x31, 0x70, 0xE4, 0xC9, 0xA3, 0x46, 0xD9, 0xAD, 0xFD, 0x78, 0x37, 0x66, 0xA6, 0x4D, 0x15,
+        0xCA, 0x33, 0xF5, 0xA7, 0x31, 0x83, 0x02, 0x96, 0x7E, 0xD0, 0x5E, 0xAC, 0xE9, 0x48, 0x03,
+        0xC7, 0xEF, 0x44, 0x81, 0x0B, 0x00, 0x90, 0xEA, 0x55, 0x41, 0xD8, 0x4E, 0x36, 0x10, 0xAC,
+        0x95, 0x92, 0x42, 0x5D, 0x92, 0xF4, 0x64, 0x7F, 0x96, 0x44, 0x59, 0x0B, 0x03, 0x4A, 0xF6,
+        0x16, 0x9F, 0xC8, 0xB9, 0x11, 0x70, 0xB8, 0x35, 0x06, 0xC4, 0x26, 0xC7, 0x6A, 0x89, 0xE4,
+        0x6F, 0x65, 0xC0, 0x9B, 0x55, 0x08, 0xEB, 0xE8, 0x37, 0x66, 0x67, 0x9E, 0x7D, 0x57, 0xA0,
+        0x25, 0x0D, 0xA4, 0x3E, 0x26, 0x8F, 0x32, 0xF6, 0xC9, 0x49, 0x50, 0x40, 0x0A, 0xED, 0x34,
+        0x94, 0x15, 0x5E, 0xE3, 0x1B, 0xD6, 0x27, 0x05, 0x00, 0x54, 0x05, 0x41, 0xFF, 0x0F, 0xFF,
+        0x01, 0x80, 0x36, 0x00, 0xFE, 0x8D, 0x38, 0x42, 0x51, 0x7E, 0x40, 0x38, 0xD5, 0x60, 0x46,
+        0x03, 0x90, 0x25, 0x00, 0x00, 0x12, 0x40, 0x00, 0x00, 0x01, 0x00, 0x54, 0x04, 0xFF, 0xFC,
+        0xFF, 0x01, 0x80, 0xFA, 0x7F, 0x00, 0xFC, 0x23, 0x10, 0x00, 0x00, 0x12, 0x40, 0x00, 0x00,
+        0x01, 0x00, 0x54, 0x04, 0xFF, 0xFC, 0xFF, 0x01, 0x00, 0xF5, 0xFF, 0x00, 0xF8, 0x4B, 0x20,
+        0x00, 0x00, 0x12, 0x40, 0x00, 0x00, 0x01, 0x00, 0x54, 0x04, 0xFF, 0x64, 0x82, 0x00, 0x80,
+        0xEF, 0xFF, 0x00, 0xF0, 0x9F, 0x40, 0xC0, 0x00, 0x00,
+    ];
+
+    fn decompress(frame: &[u8], capacity: usize) -> Result<Vec<u8>, usize> {
+        let mut out = vec![0u8; capacity];
+        let code = unsafe {
+            ZSTDv01_decompress(
+                out.as_mut_ptr() as *mut c_void,
+                capacity,
+                frame.as_ptr() as *const c_void,
+                frame.len(),
+            )
+        };
+        if ZSTDv01_isError(code) != 0 {
+            return Err(code);
+        }
+        out.truncate(code);
+        Ok(out)
+    }
+
+    fn frame_size_info(frame: &[u8]) -> (usize, u64) {
+        let mut c_size = 0usize;
+        let mut d_bound = 0u64;
+        unsafe {
+            ZSTDv01_findFrameSizeInfoLegacy(
+                frame.as_ptr() as *const c_void,
+                frame.len(),
+                &mut c_size,
+                &mut d_bound,
+            );
+        }
+        (c_size, d_bound)
+    }
+
+    #[test]
+    fn decodes_entropy_frame_byte_identically() {
+        let expected = SAMPLE.repeat(3).into_bytes();
+        let out = decompress(FRAME_ENTROPY, expected.len()).unwrap();
+        assert_eq!(out, expected);
+    }
+
+    #[test]
+    fn decodes_raw_block_frame_byte_identically() {
+        let out = decompress(FRAME_RAW, RAW_PAYLOAD.len()).unwrap();
+        assert_eq!(out, RAW_PAYLOAD);
+    }
+
+    #[test]
+    fn decodes_multi_block_frame_byte_identically() {
+        let expected = SAMPLE.repeat(1800).into_bytes();
+        assert_eq!(expected.len(), 426600);
+        let out = decompress(FRAME_MULTI_BLOCK, expected.len()).unwrap();
+        assert_eq!(out, expected);
+    }
+
+    #[test]
+    fn reports_frame_size_info_like_c() {
+        /* Values verified against the pristine C implementation. */
+        assert_eq!(
+            frame_size_info(FRAME_ENTROPY),
+            (FRAME_ENTROPY.len(), 131072)
+        );
+        assert_eq!(frame_size_info(FRAME_RAW), (FRAME_RAW.len(), 131072));
+        assert_eq!(
+            frame_size_info(FRAME_MULTI_BLOCK),
+            (FRAME_MULTI_BLOCK.len(), 524288)
+        );
+    }
+
+    #[test]
+    fn rejects_bad_magic_with_prefix_unknown() {
+        let mut frame = FRAME_ENTROPY.to_vec();
+        frame[0] ^= 0x55;
+        assert_eq!(
+            decompress(&frame, 1024).unwrap_err(),
+            ERROR(ZstdErrorCode::PrefixUnknown)
+        );
+        let (c_size, d_bound) = frame_size_info(&frame);
+        assert_eq!(c_size, ERROR(ZstdErrorCode::PrefixUnknown));
+        assert_eq!(d_bound, ZSTD_CONTENTSIZE_ERROR);
+    }
+
+    #[test]
+    fn rejects_truncated_frames_with_src_size_wrong() {
+        for frame in [FRAME_ENTROPY, FRAME_RAW, FRAME_MULTI_BLOCK] {
+            let truncated = &frame[..frame.len() - 1];
+            assert_eq!(
+                decompress(truncated, 1 << 20).unwrap_err(),
+                ERROR(ZstdErrorCode::SrcSizeWrong)
+            );
+            assert_eq!(
+                decompress(&frame[..5], 1 << 20).unwrap_err(),
+                ERROR(ZstdErrorCode::SrcSizeWrong)
+            );
+        }
+    }
+
+    #[test]
+    fn rejects_small_destination_with_dst_size_too_small() {
+        /* Error codes verified against the pristine C implementation. */
+        let expected_len = SAMPLE.len() * 3;
+        assert_eq!(
+            decompress(FRAME_ENTROPY, expected_len - 1).unwrap_err(),
+            ERROR(ZstdErrorCode::DstSizeTooSmall)
+        );
+        assert_eq!(
+            decompress(FRAME_ENTROPY, 0).unwrap_err(),
+            ERROR(ZstdErrorCode::DstSizeTooSmall)
+        );
+        assert_eq!(
+            decompress(FRAME_RAW, RAW_PAYLOAD.len() - 1).unwrap_err(),
+            ERROR(ZstdErrorCode::DstSizeTooSmall)
+        );
+    }
+
+    #[test]
+    fn streaming_api_decodes_the_frame() {
+        let expected = SAMPLE.repeat(3).into_bytes();
+        let mut out = vec![0u8; expected.len()];
+        let mut in_pos = 0usize;
+        let mut out_pos = 0usize;
+        unsafe {
+            let dctx = ZSTDv01_createDCtx();
+            assert!(!dctx.is_null());
+            loop {
+                let needed = ZSTDv01_nextSrcSizeToDecompress(dctx);
+                if needed == 0 {
+                    break;
+                }
+                assert!(in_pos + needed <= FRAME_ENTROPY.len());
+                let produced = ZSTDv01_decompressContinue(
+                    dctx,
+                    out.as_mut_ptr().add(out_pos) as *mut c_void,
+                    out.len() - out_pos,
+                    FRAME_ENTROPY.as_ptr().add(in_pos) as *const c_void,
+                    needed,
+                );
+                assert_eq!(ZSTDv01_isError(produced), 0);
+                in_pos += needed;
+                out_pos += produced;
+            }
+            assert_eq!(ZSTDv01_freeDCtx(dctx), 0);
+        }
+        assert_eq!(in_pos, FRAME_ENTROPY.len());
+        assert_eq!(out_pos, expected.len());
+        assert_eq!(out, expected);
+    }
+
+    #[test]
+    fn streaming_context_reset_and_null_free() {
+        unsafe {
+            let dctx = ZSTDv01_createDCtx();
+            assert_eq!(ZSTDv01_nextSrcSizeToDecompress(dctx), 4);
+            /* bad magic through the streaming entry point */
+            let bad = [0u8; 4];
+            assert_eq!(
+                ZSTDv01_decompressContinue(
+                    dctx,
+                    ptr::null_mut(),
+                    0,
+                    bad.as_ptr() as *const c_void,
+                    4
+                ),
+                ERROR(ZstdErrorCode::PrefixUnknown)
+            );
+            /* wrong srcSize */
+            assert_eq!(
+                ZSTDv01_decompressContinue(
+                    dctx,
+                    ptr::null_mut(),
+                    0,
+                    bad.as_ptr() as *const c_void,
+                    3
+                ),
+                ERROR(ZstdErrorCode::SrcSizeWrong)
+            );
+            assert_eq!(ZSTDv01_resetDCtx(dctx), 0);
+            assert_eq!(ZSTDv01_nextSrcSizeToDecompress(dctx), 4);
+            assert_eq!(ZSTDv01_freeDCtx(dctx), 0);
+            assert_eq!(ZSTDv01_freeDCtx(ptr::null_mut()), 0);
+        }
+    }
+}

rust/src/lib.rs

@@ -18,6 +18,7 @@ pub mod hist;
 pub mod huf_compress;
 #[cfg(feature = "decompression")]
 pub mod huf_decompress;
+pub mod legacy;
 pub mod mem;
 pub mod pool;
 pub mod threading;

rust/src/timefn.rs

@@ -0,0 +1,198 @@
+#![allow(non_camel_case_types)]
+#![allow(non_snake_case)]
+
+//! Precise monotonic time measurement for the command-line programs.
+//!
+//! Port of `programs/timefn.c`.  `UTIL_time_t` is a plain nanosecond counter
+//! whose absolute value is meaningless; only spans between two measurements
+//! are valid.  The struct crosses the C ABI by value, so it stays `repr(C)`
+//! with the exact `timefn.h` layout.
+//!
+//! Platform selection mirrors the C preprocessor structure: Windows uses the
+//! performance counter, Apple systems use the Mach absolute clock, and other
+//! POSIX systems use `clock_gettime(CLOCK_MONOTONIC)`.  The C90 `clock()`
+//! fallback is never needed on targets Rust supports, so multi-threaded
+//! measurements are always supported.
+
+use std::os::raw::c_int;
+
+/// Precise Time (`PTime` in timefn.h): an unsigned 64-bit nanosecond count.
+pub type PTime = u64;
+
+/// Nanosecond time counter with the `timefn.h` `UTIL_time_t` layout.
+#[repr(C)]
+#[derive(Clone, Copy, Debug)]
+pub struct UTIL_time_t {
+    pub t: PTime,
+}
+
+const _: () = assert!(std::mem::size_of::<PTime>() == 8);
+const _: () = assert!(std::mem::size_of::<UTIL_time_t>() == std::mem::size_of::<PTime>());
+
+#[cfg(windows)]
+mod platform {
+    use super::PTime;
+    use std::sync::OnceLock;
+
+    #[link(name = "kernel32")]
+    unsafe extern "system" {
+        /// Takes a `LARGE_INTEGER*`; the union is ABI-identical to `i64*`.
+        fn QueryPerformanceCounter(count: *mut i64) -> i32;
+        fn QueryPerformanceFrequency(frequency: *mut i64) -> i32;
+    }
+
+    pub fn monotonic_ns() -> PTime {
+        static TICKS_PER_SECOND: OnceLock<i64> = OnceLock::new();
+        let ticks_per_second = *TICKS_PER_SECOND.get_or_init(|| {
+            let mut frequency = 0i64;
+            if unsafe { QueryPerformanceFrequency(&mut frequency) } == 0 {
+                eprintln!(
+                    "timefn::QueryPerformanceFrequency: {}",
+                    std::io::Error::last_os_error()
+                );
+                std::process::abort();
+            }
+            frequency
+        });
+        let mut counter = 0i64;
+        unsafe { QueryPerformanceCounter(&mut counter) };
+        (counter as PTime).wrapping_mul(1_000_000_000) / ticks_per_second as PTime
+    }
+}
+
+#[cfg(all(unix, target_vendor = "apple"))]
+mod platform {
+    use super::PTime;
+    use std::sync::OnceLock;
+
+    pub fn monotonic_ns() -> PTime {
+        static RATE: OnceLock<(PTime, PTime)> = OnceLock::new();
+        let (numer, denom) = *RATE.get_or_init(|| {
+            let mut rate = libc::mach_timebase_info { numer: 0, denom: 0 };
+            unsafe { libc::mach_timebase_info(&mut rate) };
+            (PTime::from(rate.numer), PTime::from(rate.denom))
+        });
+        unsafe { libc::mach_absolute_time() }.wrapping_mul(numer) / denom
+    }
+}
+
+#[cfg(all(unix, not(target_vendor = "apple")))]
+mod platform {
+    use super::PTime;
+
+    pub fn monotonic_ns() -> PTime {
+        // Zero-initialized like the C source, which works around timespec_get
+        // msan limitations on some targets.
+        let mut time: libc::timespec = unsafe { std::mem::zeroed() };
+        if unsafe { libc::clock_gettime(libc::CLOCK_MONOTONIC, &mut time) } != 0 {
+            eprintln!(
+                "timefn::clock_gettime(CLOCK_MONOTONIC): {}",
+                std::io::Error::last_os_error()
+            );
+            std::process::abort();
+        }
+        (time.tv_sec as PTime)
+            .wrapping_mul(1_000_000_000)
+            .wrapping_add(time.tv_nsec as PTime)
+    }
+}
+
+/// Returns the current value of the platform's monotonic nanosecond clock.
+#[no_mangle]
+pub extern "C" fn UTIL_getTime() -> UTIL_time_t {
+    UTIL_time_t {
+        t: platform::monotonic_ns(),
+    }
+}
+
+/// Nanoseconds elapsed between two measurements, with C unsigned wrap-around.
+#[no_mangle]
+pub extern "C" fn UTIL_getSpanTimeNano(clockStart: UTIL_time_t, clockEnd: UTIL_time_t) -> PTime {
+    clockEnd.t.wrapping_sub(clockStart.t)
+}
+
+/// Microseconds elapsed between two measurements, truncated like C division.
+#[no_mangle]
+pub extern "C" fn UTIL_getSpanTimeMicro(begin: UTIL_time_t, end: UTIL_time_t) -> PTime {
+    UTIL_getSpanTimeNano(begin, end) / 1000
+}
+
+/// Microseconds elapsed since `clockStart`.
+#[no_mangle]
+pub extern "C" fn UTIL_clockSpanMicro(clockStart: UTIL_time_t) -> PTime {
+    UTIL_getSpanTimeMicro(clockStart, UTIL_getTime())
+}
+
+/// Nanoseconds elapsed since `clockStart`.
+#[no_mangle]
+pub extern "C" fn UTIL_clockSpanNano(clockStart: UTIL_time_t) -> PTime {
+    UTIL_getSpanTimeNano(clockStart, UTIL_getTime())
+}
+
+/// Busy-waits until the clock produces a new tick, improving measurement
+/// accuracy on platforms with a low timer resolution.
+#[no_mangle]
+pub extern "C" fn UTIL_waitForNextTick() {
+    let clockStart = UTIL_getTime();
+    loop {
+        let clockEnd = UTIL_getTime();
+        if UTIL_getSpanTimeNano(clockStart, clockEnd) != 0 {
+            return;
+        }
+    }
+}
+
+/// All clock sources used by the Rust port are valid under multi-threaded
+/// workloads; only the C90 `clock()` fallback of the C source was not.
+#[no_mangle]
+pub extern "C" fn UTIL_support_MT_measurements() -> c_int {
+    1
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn nanosecond_spans_subtract_with_unsigned_wrap_around() {
+        let start = UTIL_time_t { t: 100 };
+        let end = UTIL_time_t { t: 350 };
+
+        assert_eq!(UTIL_getSpanTimeNano(start, end), 250);
+        assert_eq!(UTIL_getSpanTimeNano(end, start), u64::MAX - 249);
+        assert_eq!(UTIL_getSpanTimeNano(start, start), 0);
+    }
+
+    #[test]
+    fn microsecond_spans_truncate_sub_tick_remainders() {
+        let start = UTIL_time_t { t: 0 };
+
+        assert_eq!(UTIL_getSpanTimeMicro(start, UTIL_time_t { t: 999 }), 0);
+        assert_eq!(UTIL_getSpanTimeMicro(start, UTIL_time_t { t: 1_000 }), 1);
+        assert_eq!(UTIL_getSpanTimeMicro(start, UTIL_time_t { t: 1_999 }), 1);
+        assert_eq!(UTIL_getSpanTimeMicro(start, UTIL_time_t { t: 2_000 }), 2);
+    }
+
+    #[test]
+    fn clock_is_monotonic_across_measurements() {
+        let first = UTIL_getTime();
+        let second = UTIL_getTime();
+
+        assert!(second.t >= first.t);
+        assert!(UTIL_clockSpanNano(first) >= UTIL_getSpanTimeNano(first, second));
+    }
+
+    #[test]
+    fn waiting_for_the_next_tick_advances_the_clock() {
+        let before = UTIL_getTime();
+        UTIL_waitForNextTick();
+        let after = UTIL_getTime();
+
+        assert!(UTIL_getSpanTimeNano(before, after) > 0);
+    }
+
+    #[test]
+    fn multi_threaded_measurements_are_supported() {
+        assert_eq!(UTIL_support_MT_measurements(), 1);
+    }
+}

rust/src/zstd_cli.rs

@@ -10,9 +10,15 @@
 //! writes, dictionary loading, streaming, and metadata preservation remain in
 //! `programs/fileio.c` for this first migration step.
 //!
+//! Benchmark mode (`-b`) parses here and dispatches through the
+//! `ZSTD_rust_cli_bench` bridge in `programs/zstdcli.c`: the run/timing loop
+//! (benchfn, timefn) is Rust, while orchestration and result formatting
+//! (`benchzstd.c`) remain C behind the preprocessor-gated bridge, so builds
+//! with `ZSTD_NOBENCH` never reference benchmark symbols.
+//!
 //! Remaining C-only CLI boundaries are called out in `unsupported()` below:
-//! benchmark execution, dictionary training, recursive/file-list expansion,
+//! dictionary training, recursive/file-list expansion, tracing,
-//! tracing, alternate-format selection, and the advanced directory modes.
+//! alternate-format selection, and the advanced directory modes.
 
 use std::env;
 use std::ffi::{CStr, CString, OsStr, OsString};
@@ -30,6 +36,7 @@ use std::os::unix::fs::FileTypeExt;
 const DEFAULT_CLEVEL: i32 = 3;
 #[cfg(feature = "compression")]
 const DEFAULT_MAX_CLEVEL: i32 = 19;
+const DEFAULT_BENCH_NB_SECONDS: u32 = 3;
 const DEFAULT_MEM_LIMIT: u32 = 1 << 27;
 const DEFAULT_LONG_WINDOW_LOG: u32 = 27;
 const MAX_FAST_ACCELERATION: i32 = 128 << 10;
@@ -173,6 +180,22 @@ unsafe extern "C" {
         output: *const c_char,
         dict: *const c_char,
     ) -> c_int;
+
+    /// Benchmark bridge implemented by the `programs/zstdcli.c` shim, which
+    /// owns the `ZSTD_NOBENCH` preprocessor decision. Returns the benchmark
+    /// result (>= 0), or -1 when benchmarking is compiled out.
+    fn ZSTD_rust_cli_bench(
+        file_names: *const *const c_char,
+        nb_files: c_uint,
+        dict_file_name: *const c_char,
+        start_level: c_int,
+        end_level: c_int,
+        compression_params: *const ZSTD_compressionParameters,
+        display_level: c_int,
+        nb_seconds: c_uint,
+        block_size: usize,
+        nb_workers: c_int,
+    ) -> c_int;
 }
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
@@ -180,6 +203,7 @@ enum Operation {
     Compress,
     Decompress,
     Test,
+    Bench,
 }
 
 #[derive(Debug)]
@@ -230,6 +254,8 @@ struct Cli {
     row_match_finder: i32,
     exclude_compressed: bool,
     compression_params: ZSTD_compressionParameters,
+    bench_end_level: Option<i32>,
+    bench_nb_seconds: Option<u32>,
     unsupported_program: Option<String>,
 }
 
@@ -275,6 +301,8 @@ impl Cli {
             row_match_finder: ZSTD_PS_AUTO,
             exclude_compressed: false,
             compression_params: ZSTD_compressionParameters::default(),
+            bench_end_level: None,
+            bench_nb_seconds: None,
             unsupported_program: None,
         };
 
@@ -404,9 +432,22 @@ fn usage(advanced: bool) {
             out,
             "  --adapt[=min=#,max=#], --rsyncable, --[no-]row-match-finder"
         );
+        let _ = writeln!(out, "\nBenchmark options:");
         let _ = writeln!(
             out,
-            "\nNot yet migrated: benchmark, dictionary training, recursive/file-list expansion,"
+            "  -b#                           Benchmark file(s) at compression level #"
+        );
+        let _ = writeln!(
+            out,
+            "  -e#                           Test all levels from -b# up to # included"
+        );
+        let _ = writeln!(
+            out,
+            "  -i#                           Set the minimum evaluation time to # seconds"
+        );
+        let _ = writeln!(
+            out,
+            "\nNot yet migrated: dictionary training, recursive/file-list expansion,"
         );
         let _ = writeln!(out, "trace, alternate formats, and output-directory modes.");
     }
@@ -905,6 +946,33 @@ fn parse_short_options(
             'd' => cli.operation = Operation::Decompress,
             'z' => cli.operation = Operation::Compress,
             't' => cli.operation = Operation::Test,
+            'b' => cli.operation = Operation::Bench,
+            'e' | 'i' => {
+                // Benchmark range end (-e#) and duration (-i#): like the C
+                // parser, digits attach directly and default to 0.
+                let mut digits_end = offset + 1;
+                while digits_end < bytes.len() && bytes[digits_end].is_ascii_digit() {
+                    digits_end += 1;
+                }
+                let digits = &value[offset + 1..digits_end];
+                if option == 'e' {
+                    cli.bench_end_level = Some(if digits.is_empty() {
+                        0
+                    } else {
+                        parse_i32(digits, "benchmark end level")?
+                    });
+                } else {
+                    cli.bench_nb_seconds = Some(if digits.is_empty() {
+                        0
+                    } else {
+                        digits
+                            .parse::<u32>()
+                            .map_err(|_| format!("invalid benchmark duration: {digits:?}"))?
+                    });
+                }
+                offset = digits_end;
+                continue;
+            }
             'c' => {
                 cli.output = Some(cstring(STDOUT_MARK)?);
                 cli.force_stdout = true;
@@ -940,7 +1008,7 @@ fn parse_short_options(
                 }
                 break;
             }
-            'b' | 'e' | 'i' | 'l' | 'p' | 'P' | 'r' | 's' | 'S' => {
+            'l' | 'p' | 'P' | 'r' | 's' | 'S' => {
                 unsupported(&format!("-{option}"))?;
             }
             _ => return Err(format!("unknown option -{option}")),
@@ -1231,16 +1299,52 @@ unsafe fn run_decompress(
                 dictionary,
             )
         },
-        Operation::Compress => unreachable!("compression is dispatched separately"),
+        Operation::Compress | Operation::Bench => {
+            unreachable!("compression and benchmark are dispatched separately")
+        }
     }
 }
 
+/// Runs benchmark mode through the C bridge. Level clamping against
+/// `ZSTD_maxCLevel()` happens on the C side, where the symbol is always
+/// available when benchmarking is compiled in. No input file means a
+/// synthetic-sample benchmark, matching the C CLI.
+fn run_bench(cli: &Cli) -> Result<i32, String> {
+    let inputs: Vec<*const c_char> = cli.inputs.iter().map(|value| value.as_ptr()).collect();
+    let dictionary = cli
+        .dictionary
+        .as_ref()
+        .map_or(ptr::null(), |value| value.as_ptr());
+    let result = unsafe {
+        ZSTD_rust_cli_bench(
+            inputs.as_ptr(),
+            inputs.len() as c_uint,
+            dictionary,
+            cli.level,
+            cli.bench_end_level.unwrap_or(cli.level),
+            &cli.compression_params,
+            cli.display_level,
+            cli.bench_nb_seconds.unwrap_or(DEFAULT_BENCH_NB_SECONDS),
+            cli.block_size.unwrap_or(0),
+            // The C CLI benchmarks single-threaded unless -T was given.
+            cli.workers.unwrap_or(1),
+        )
+    };
+    if result < 0 {
+        return Err("benchmark mode is not available in this build".to_owned());
+    }
+    Ok(result)
+}
+
 fn run_cli(mut cli: Cli) -> Result<i32, String> {
     if let Some(program_name) = &cli.unsupported_program {
         return Err(format!(
             "{program_name} compatibility mode is not yet implemented by the Rust CLI frontend"
         ));
     }
+    if cli.operation == Operation::Bench {
+        return run_bench(&cli);
+    }
     let explicit_input_count = cli.inputs.len();
     filter_symlink_inputs(&mut cli);
     if explicit_input_count > 0 && cli.inputs.is_empty() {
@@ -1347,6 +1451,7 @@ fn run_cli(mut cli: Cli) -> Result<i32, String> {
                 #[cfg(not(feature = "decompression"))]
                 unreachable!("unsupported decompression was rejected above")
             }
+            Operation::Bench => unreachable!("benchmark mode was dispatched earlier"),
         }
     };
 
@@ -1581,4 +1686,41 @@ mod tests {
 
         assert!(error.contains("not yet implemented"));
     }
+
+    #[test]
+    fn bench_mode_parses_level_duration_and_defaults() {
+        let cli = parse(&["zstd", "-b1", "-i0", "input"]);
+
+        assert_eq!(cli.operation, Operation::Bench);
+        assert_eq!(cli.level, 1);
+        assert_eq!(cli.bench_nb_seconds, Some(0));
+        assert_eq!(cli.bench_end_level, None);
+        assert_eq!(
+            cli.inputs
+                .iter()
+                .map(|input| input.as_bytes())
+                .collect::<Vec<_>>(),
+            vec![&b"input"[..]]
+        );
+    }
+
+    #[test]
+    fn bench_range_aggregates_within_a_single_argument() {
+        let cli = parse(&["zstd", "-b5e6i2", "input"]);
+
+        assert_eq!(cli.operation, Operation::Bench);
+        assert_eq!(cli.level, 5);
+        assert_eq!(cli.bench_end_level, Some(6));
+        assert_eq!(cli.bench_nb_seconds, Some(2));
+    }
+
+    #[test]
+    fn bench_duration_without_digits_defaults_to_zero() {
+        let cli = parse(&["zstd", "-b", "-e", "-i"]);
+
+        assert_eq!(cli.operation, Operation::Bench);
+        assert_eq!(cli.level, DEFAULT_CLEVEL);
+        assert_eq!(cli.bench_end_level, Some(0));
+        assert_eq!(cli.bench_nb_seconds, Some(0));
+    }
 }

tests/Makefile

@@ -65,16 +65,24 @@ endif
 endif
 
 RUST_HUF_FEATURE :=
-RUST_BUILD_CONFIG := default
+RUST_HUF_MODE := default
 ifneq ($(RUST_HUF_FORCE_X1),0)
 RUST_HUF_FEATURE := huf-force-decompress-x1
-RUST_BUILD_CONFIG := huf-force-decompress-x1
+RUST_HUF_MODE := huf-force-decompress-x1
 endif
 ifneq ($(RUST_HUF_FORCE_X2),0)
 RUST_HUF_FEATURE := huf-force-decompress-x2
-RUST_BUILD_CONFIG := huf-force-decompress-x2
+RUST_HUF_MODE := huf-force-decompress-x2
 endif
 
+# Test binaries compile every lib/legacy/*.c file regardless of the dispatch
+# level (ZSTDLEGACY_FILES is a plain wildcard below), so the Rust archive must
+# always carry all ported legacy decoders too.  The build configuration still
+# encodes the level because the flat C objects bake -DZSTD_LEGACY_SUPPORT into
+# the dispatch code and must never outlive a level change.
+RUST_LEGACY_FEATURES := legacy-v01,legacy-v02,legacy-v03,legacy-v04,legacy-v05,legacy-v06,legacy-v07
+RUST_BUILD_CONFIG := $(RUST_HUF_MODE)-legacy$(ZSTD_LEGACY_SUPPORT)
+
 RUST_TARGET_DIR := $(RUST_DIR)/target/$(RUST_BUILD_CONFIG)
 RUST_STATICLIB := $(RUST_TARGET_DIR)/release/libzstd_rs.a
 RUST_TARGET_32 ?= i686-unknown-linux-gnu
@@ -86,6 +94,7 @@ RUST_CARGO_FLAGS := --manifest-path $(RUST_MANIFEST) --release \
 ifneq ($(RUST_HUF_FEATURE),)
 RUST_CARGO_FLAGS += --features $(RUST_HUF_FEATURE)
 endif
+RUST_CARGO_FLAGS += --features $(RUST_LEGACY_FEATURES)
 
 $(RUST_STATICLIB): $(RUST_SOURCES)
 	$(CARGO) build $(RUST_CARGO_FLAGS)
@@ -93,6 +102,28 @@ $(RUST_STATICLIB): $(RUST_SOURCES)
 $(RUST_STATICLIB_32): $(RUST_SOURCES)
 	$(CARGO) build $(RUST_CARGO_FLAGS) --target $(RUST_TARGET_32)
 
+# Program-only helpers that were C sources shared with the tests (timefn,
+# benchfn) now live in the Rust CLI package. The tests link a helpers-only
+# archive, built without the `cli` feature: the parser/dispatch layer needs
+# the C fileio backend, which test binaries do not provide.
+RUST_CLI_DIR := $(RUST_DIR)/cli
+RUST_CLI_MANIFEST := $(RUST_CLI_DIR)/Cargo.toml
+RUST_CLI_HELPER_SOURCES := $(RUST_CLI_MANIFEST) $(RUST_CLI_DIR)/Cargo.lock \
+                           $(RUST_CLI_DIR)/src/lib.rs \
+                           $(RUST_DIR)/src/timefn.rs $(RUST_DIR)/src/benchfn.rs
+RUST_CLI_HELPERS_TARGET_DIR := $(RUST_DIR)/target/cli-helpers
+RUST_CLI_HELPERS_STATICLIB := $(RUST_CLI_HELPERS_TARGET_DIR)/release/libzstd_cli_rs.a
+RUST_CLI_HELPERS_STATICLIB_32 := $(RUST_CLI_HELPERS_TARGET_DIR)/$(RUST_TARGET_32)/release/libzstd_cli_rs.a
+RUST_CLI_HELPERS_CARGO_FLAGS := --manifest-path $(RUST_CLI_MANIFEST) --release \
+                                --target-dir $(RUST_CLI_HELPERS_TARGET_DIR) \
+                                --no-default-features
+
+$(RUST_CLI_HELPERS_STATICLIB): $(RUST_CLI_HELPER_SOURCES)
+	$(CARGO) build $(RUST_CLI_HELPERS_CARGO_FLAGS)
+
+$(RUST_CLI_HELPERS_STATICLIB_32): $(RUST_CLI_HELPER_SOURCES)
+	$(CARGO) build $(RUST_CLI_HELPERS_CARGO_FLAGS) --target $(RUST_TARGET_32)
+
 # These test objects have flat filenames, unlike the configuration-hashed
 # program objects. Track the HUF mode separately so a C object set compiled
 # for one decoder is never relinked with a Rust archive for another decoder.
@@ -252,8 +283,8 @@ fuzzer32 : $(ZSTD_FILES)
 	$(LINK.c) $^ -o $@$(EXT)
 
 # note : broken : requires symbols unavailable from dynamic library
-fuzzer-dll : $(LIB_SRCDIR)/common/xxhash.c $(PRGDIR)/util.c $(PRGDIR)/timefn.c $(PRGDIR)/datagen.c fuzzer.c
+fuzzer-dll : $(LIB_SRCDIR)/common/xxhash.c $(PRGDIR)/util.c $(PRGDIR)/timefn.c $(PRGDIR)/datagen.c fuzzer.c $(RUST_CLI_HELPERS_STATICLIB)
-	$(CC) $(CPPFLAGS) $(CFLAGS) $(filter %.c,$^) $(LDFLAGS) -o $@$(EXT)
+	$(CC) $(CPPFLAGS) $(CFLAGS) $(filter %.c,$^) $(RUST_CLI_HELPERS_STATICLIB) $(LDFLAGS) -o $@$(EXT)
 
 CLEAN += zstreamtest zstreamtest32
 ZSTREAM_LOCAL_FILES := $(PRGDIR)/datagen.c $(PRGDIR)/util.c $(PRGDIR)/timefn.c seqgen.c zstreamtest.c external_matchfinder.c
@@ -284,8 +315,8 @@ zstreamtest_ubsan : $(ZSTREAMFILES)
 
 # note : broken : requires symbols unavailable from dynamic library
 zstreamtest-dll : $(LIB_SRCDIR)/common/xxhash.c  # xxh symbols not exposed from dll
-zstreamtest-dll : $(ZSTREAM_LOCAL_FILES)
+zstreamtest-dll : $(ZSTREAM_LOCAL_FILES) $(RUST_CLI_HELPERS_STATICLIB)
-	$(CC) $(CPPFLAGS) $(CFLAGS) $(filter %.c,$^) $(LDFLAGS) -o $@$(EXT)
+	$(CC) $(CPPFLAGS) $(CFLAGS) $(filter %.c,$^) $(RUST_CLI_HELPERS_STATICLIB) $(LDFLAGS) -o $@$(EXT)
 
 CLEAN += paramgrill
 paramgrill : DEBUGFLAGS =   # turn off debug for speed measurements
@@ -344,6 +375,17 @@ $(RUST_LINK_TARGETS_32): $(RUST_STATICLIB_32)
 
 $(RUST_LINK_TARGETS) $(RUST_LINK_TARGETS_32): $(RUST_HUF_C_MODE_STAMP)
 
+# Tests that compile the timefn/benchfn C shims also link the Rust CLI
+# helpers archive, which owns those implementations. The archive is a
+# prerequisite so `$^` places it after every C object referencing its symbols.
+RUST_CLI_LINK_TARGETS := fullbench fullbench-lib fullbench-dll fuzzer \
+                         zstreamtest zstreamtest_asan zstreamtest_tsan \
+                         zstreamtest_ubsan paramgrill decodecorpus poolTests
+$(RUST_CLI_LINK_TARGETS): $(RUST_CLI_HELPERS_STATICLIB)
+
+RUST_CLI_LINK_TARGETS_32 := fullbench32 fuzzer32 zstreamtest32
+$(RUST_CLI_LINK_TARGETS_32): $(RUST_CLI_HELPERS_STATICLIB_32)
+
 .PHONY: versionsTest
 versionsTest: clean
 	$(PYTHON) test-zstd-versions.py