feat(cli): support --single-thread in the Rust frontend

The Rust CLI frontend rejected --single-thread, but tests/playTests.sh
uses it 28 times, so the flag is required before the original CLI test
suite can gate the migration.

Mirror the C zstdcli.c semantics: --single-thread pins zero workers and
sets a latch that suppresses the automatic core-count resolution, so
fileio receives nbWorkers == 0 and runs its single-thread streaming
mode (slightly different from -T1, which uses one worker thread).  A
bare zero from -T0 or the zstdmt program name still auto-detects the
core count, and a later -T# overrides the pinned worker count while the
latch stays set, exactly as the C variable pair behaved.

Test plan:
- cd rust/cli && cargo clippy --all-targets -- -D warnings && cargo
  test --all-targets (plus the compression-only and decompression-only
  feature matrices); new parser tests cover the flag, the -T override
  order, and rejection of an attached value.
- make -C programs zstd, then: --single-thread -3/-19 round-trips
  against COPYING via cmp; --single-thread=1 fails with "does not take
  an argument".

lib/compress/zstd_compress.c

@@ -38,6 +38,62 @@ size_t ZSTD_rust_writeFrameHeader(void* dst, size_t dstCapacity,
                                   U32 windowLog, U64 pledgedSrcSize,
                                   U32 dictID);
 
+/* Context-free compression-parameter selection and sizing leaves live in
+ * Rust (rust/src/zstd_compress_params.rs).  This file retains
+ * configuration-sensitive policy: the excluded-block-compressor strategy
+ * cascade, private ZSTD_CCtx_params handling, and sanitizer workspace
+ * policy, which it feeds to the leaves as explicit scalar inputs.  The
+ * ZSTD_CParamMode_e and ZSTD_ParamSwitch_e enums are passed as int; the
+ * Rust side mirrors their values. */
+int ZSTD_rust_params_maxCLevel(void);
+int ZSTD_rust_params_minCLevel(void);
+int ZSTD_rust_params_defaultCLevel(void);
+ZSTD_bounds ZSTD_rust_params_getBounds(int param);
+size_t ZSTD_rust_params_checkCParams(ZSTD_compressionParameters cParams);
+ZSTD_compressionParameters
+ZSTD_rust_params_clampCParams(ZSTD_compressionParameters cParams);
+U32 ZSTD_rust_params_cycleLog(U32 hashLog, int strategy);
+ZSTD_compressionParameters
+ZSTD_rust_params_selectCParams(int compressionLevel, U64 srcSizeHint,
+                               size_t dictSize, int mode);
+ZSTD_compressionParameters
+ZSTD_rust_params_adjustCParams(ZSTD_compressionParameters cParams, U64 srcSize,
+                               size_t dictSize, int mode,
+                               int useRowMatchFinder);
+ZSTD_parameters ZSTD_rust_params_makeParams(ZSTD_compressionParameters cParams);
+size_t ZSTD_rust_params_maxNbSeq(size_t blockSize, U32 minMatch,
+                                 int useSequenceProducer);
+size_t ZSTD_rust_params_resolveMaxBlockSize(size_t maxBlockSize);
+
+typedef struct {
+    U32 hashLog3Max;
+    size_t matchTSize;
+    size_t optimalTSize;
+    size_t asanRedzoneSize;
+} ZSTD_rustMatchStateSizing;
+size_t ZSTD_rust_params_estimateMatchStateSize(
+        ZSTD_compressionParameters cParams, int useRowMatchFinder,
+        int enableDedicatedDictSearch, U32 forCCtx,
+        const ZSTD_rustMatchStateSizing* sizing);
+
+typedef struct {
+    size_t cdictSize;
+    size_t hufWorkspaceSize;
+    U32 hashLog3Max;
+    size_t matchTSize;
+    size_t optimalTSize;
+    size_t asanRedzoneSize;
+} ZSTD_rustCDictSizing;
+size_t ZSTD_rust_params_estimateCDictSizeFromCParams(
+        size_t dictSize, ZSTD_compressionParameters cParams,
+        int dictLoadMethod, const ZSTD_rustCDictSizing* sizing);
+
+#if ZSTD_ADDRESS_SANITIZER && !defined (ZSTD_ASAN_DONT_POISON_WORKSPACE)
+#  define ZSTD_RUST_ASAN_REDZONE_SIZE ((size_t)ZSTD_CWKSP_ASAN_REDZONE_SIZE)
+#else
+#  define ZSTD_RUST_ASAN_REDZONE_SIZE ((size_t)0)
+#endif
+
 /* ***************************************************************
 *  Tuning parameters
 *****************************************************************/
@@ -276,11 +332,7 @@ static int ZSTD_resolveExternalSequenceValidation(int mode) {
 
 /* Resolves maxBlockSize to the default if no value is present. */
 static size_t ZSTD_resolveMaxBlockSize(size_t maxBlockSize) {
-    if (maxBlockSize == 0) {
-        return ZSTD_BLOCKSIZE_MAX;
-    } else {
-        return maxBlockSize;
-    }
+    return ZSTD_rust_params_resolveMaxBlockSize(maxBlockSize);
 }
 
 static ZSTD_ParamSwitch_e ZSTD_resolveExternalRepcodeSearch(ZSTD_ParamSwitch_e value, int cLevel) {
@@ -420,45 +472,17 @@ ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter param)
 
     switch(param)
     {
+    /* The compression level and the seven core compression parameters are
+     * bounded by the Rust leaf. */
     case ZSTD_c_compressionLevel:
-        bounds.lowerBound = ZSTD_minCLevel();
-        bounds.upperBound = ZSTD_maxCLevel();
-        return bounds;
-
     case ZSTD_c_windowLog:
-        bounds.lowerBound = ZSTD_WINDOWLOG_MIN;
-        bounds.upperBound = ZSTD_WINDOWLOG_MAX;
-        return bounds;
-
     case ZSTD_c_hashLog:
-        bounds.lowerBound = ZSTD_HASHLOG_MIN;
-        bounds.upperBound = ZSTD_HASHLOG_MAX;
-        return bounds;
-
     case ZSTD_c_chainLog:
-        bounds.lowerBound = ZSTD_CHAINLOG_MIN;
-        bounds.upperBound = ZSTD_CHAINLOG_MAX;
-        return bounds;
-
     case ZSTD_c_searchLog:
-        bounds.lowerBound = ZSTD_SEARCHLOG_MIN;
-        bounds.upperBound = ZSTD_SEARCHLOG_MAX;
-        return bounds;
-
     case ZSTD_c_minMatch:
-        bounds.lowerBound = ZSTD_MINMATCH_MIN;
-        bounds.upperBound = ZSTD_MINMATCH_MAX;
-        return bounds;
-
     case ZSTD_c_targetLength:
-        bounds.lowerBound = ZSTD_TARGETLENGTH_MIN;
-        bounds.upperBound = ZSTD_TARGETLENGTH_MAX;
-        return bounds;
-
     case ZSTD_c_strategy:
-        bounds.lowerBound = ZSTD_STRATEGY_MIN;
-        bounds.upperBound = ZSTD_STRATEGY_MAX;
-        return bounds;
+        return ZSTD_rust_params_getBounds((int)param);
 
     case ZSTD_c_contentSizeFlag:
         bounds.lowerBound = 0;
@@ -1385,14 +1409,7 @@ size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset)
     @return : 0, or an error code if one value is beyond authorized range */
 size_t ZSTD_checkCParams(ZSTD_compressionParameters cParams)
 {
-    BOUNDCHECK(ZSTD_c_windowLog, (int)cParams.windowLog);
-    BOUNDCHECK(ZSTD_c_chainLog,  (int)cParams.chainLog);
-    BOUNDCHECK(ZSTD_c_hashLog,   (int)cParams.hashLog);
-    BOUNDCHECK(ZSTD_c_searchLog, (int)cParams.searchLog);
-    BOUNDCHECK(ZSTD_c_minMatch,  (int)cParams.minMatch);
-    BOUNDCHECK(ZSTD_c_targetLength,(int)cParams.targetLength);
-    BOUNDCHECK(ZSTD_c_strategy,  (int)cParams.strategy);
-    return 0;
+    return ZSTD_rust_params_checkCParams(cParams);
 }
 
 /** ZSTD_clampCParams() :
@@ -1401,63 +1418,14 @@ size_t ZSTD_checkCParams(ZSTD_compressionParameters cParams)
 static ZSTD_compressionParameters
 ZSTD_clampCParams(ZSTD_compressionParameters cParams)
 {
-#   define CLAMP_TYPE(cParam, val, type)                                      \
-        do {                                                                  \
-            ZSTD_bounds const bounds = ZSTD_cParam_getBounds(cParam);         \
-            if ((int)val<bounds.lowerBound) val=(type)bounds.lowerBound;      \
-            else if ((int)val>bounds.upperBound) val=(type)bounds.upperBound; \
-        } while (0)
-#   define CLAMP(cParam, val) CLAMP_TYPE(cParam, val, unsigned)
-    CLAMP(ZSTD_c_windowLog, cParams.windowLog);
-    CLAMP(ZSTD_c_chainLog,  cParams.chainLog);
-    CLAMP(ZSTD_c_hashLog,   cParams.hashLog);
-    CLAMP(ZSTD_c_searchLog, cParams.searchLog);
-    CLAMP(ZSTD_c_minMatch,  cParams.minMatch);
-    CLAMP(ZSTD_c_targetLength,cParams.targetLength);
-    CLAMP_TYPE(ZSTD_c_strategy,cParams.strategy, ZSTD_strategy);
-    return cParams;
+    return ZSTD_rust_params_clampCParams(cParams);
 }
 
 /** ZSTD_cycleLog() :
  *  condition for correct operation : hashLog > 1 */
 U32 ZSTD_cycleLog(U32 hashLog, ZSTD_strategy strat)
 {
-    U32 const btScale = ((U32)strat >= (U32)ZSTD_btlazy2);
-    return hashLog - btScale;
-}
-
-/** ZSTD_dictAndWindowLog() :
- * Returns an adjusted window log that is large enough to fit the source and the dictionary.
- * The zstd format says that the entire dictionary is valid if one byte of the dictionary
- * is within the window. So the hashLog and chainLog should be large enough to reference both
- * the dictionary and the window. So we must use this adjusted dictAndWindowLog when downsizing
- * the hashLog and windowLog.
- * NOTE: srcSize must not be ZSTD_CONTENTSIZE_UNKNOWN.
- */
-static U32 ZSTD_dictAndWindowLog(U32 windowLog, U64 srcSize, U64 dictSize)
-{
-    const U64 maxWindowSize = 1ULL << ZSTD_WINDOWLOG_MAX;
-    /* No dictionary ==> No change */
-    if (dictSize == 0) {
-        return windowLog;
-    }
-    assert(windowLog <= ZSTD_WINDOWLOG_MAX);
-    assert(srcSize != ZSTD_CONTENTSIZE_UNKNOWN); /* Handled in ZSTD_adjustCParams_internal() */
-    {
-        U64 const windowSize = 1ULL << windowLog;
-        U64 const dictAndWindowSize = dictSize + windowSize;
-        /* If the window size is already large enough to fit both the source and the dictionary
-         * then just use the window size. Otherwise adjust so that it fits the dictionary and
-         * the window.
-         */
-        if (windowSize >= dictSize + srcSize) {
-            return windowLog; /* Window size large enough already */
-        } else if (dictAndWindowSize >= maxWindowSize) {
-            return ZSTD_WINDOWLOG_MAX; /* Larger than max window log */
-        } else  {
-            return ZSTD_highbit32((U32)dictAndWindowSize - 1) + 1;
-        }
-    }
+    return ZSTD_rust_params_cycleLog(hashLog, (int)strat);
 }
 
 /** ZSTD_adjustCParams_internal() :
@@ -1474,8 +1442,6 @@ ZSTD_adjustCParams_internal(ZSTD_compressionParameters cPar,
                             ZSTD_CParamMode_e mode,
                             ZSTD_ParamSwitch_e useRowMatchFinder)
 {
-    const U64 minSrcSize = 513; /* (1<<9) + 1 */
-    const U64 maxWindowResize = 1ULL << (ZSTD_WINDOWLOG_MAX-1);
     assert(ZSTD_checkCParams(cPar)==0);
 
     /* Cascade the selected strategy down to the next-highest one built into
@@ -1520,90 +1486,13 @@ ZSTD_adjustCParams_internal(ZSTD_compressionParameters cPar,
     }
 #endif
 
-    switch (mode) {
-    case ZSTD_cpm_unknown:
-    case ZSTD_cpm_noAttachDict:
-        /* If we don't know the source size, don't make any
-         * assumptions about it. We will already have selected
-         * smaller parameters if a dictionary is in use.
-         */
-        break;
-    case ZSTD_cpm_createCDict:
-        /* Assume a small source size when creating a dictionary
-         * with an unknown source size.
-         */
-        if (dictSize && srcSize == ZSTD_CONTENTSIZE_UNKNOWN)
-            srcSize = minSrcSize;
-        break;
-    case ZSTD_cpm_attachDict:
-        /* Dictionary has its own dedicated parameters which have
-         * already been selected. We are selecting parameters
-         * for only the source.
-         */
-        dictSize = 0;
-        break;
-    default:
-        assert(0);
-        break;
-    }
-
-    /* resize windowLog if input is small enough, to use less memory */
-    if ( (srcSize <= maxWindowResize)
-      && (dictSize <= maxWindowResize) )  {
-        U32 const tSize = (U32)(srcSize + dictSize);
-        static U32 const hashSizeMin = 1 << ZSTD_HASHLOG_MIN;
-        U32 const srcLog = (tSize < hashSizeMin) ? ZSTD_HASHLOG_MIN :
-                            ZSTD_highbit32(tSize-1) + 1;
-        if (cPar.windowLog > srcLog) cPar.windowLog = srcLog;
-    }
-    if (srcSize != ZSTD_CONTENTSIZE_UNKNOWN) {
-        U32 const dictAndWindowLog = ZSTD_dictAndWindowLog(cPar.windowLog, (U64)srcSize, (U64)dictSize);
-        U32 const cycleLog = ZSTD_cycleLog(cPar.chainLog, cPar.strategy);
-        if (cPar.hashLog > dictAndWindowLog+1) cPar.hashLog = dictAndWindowLog+1;
-        if (cycleLog > dictAndWindowLog)
-            cPar.chainLog -= (cycleLog - dictAndWindowLog);
-    }
-
-    if (cPar.windowLog < ZSTD_WINDOWLOG_ABSOLUTEMIN)
-        cPar.windowLog = ZSTD_WINDOWLOG_ABSOLUTEMIN;  /* minimum wlog required for valid frame header */
-
-    /* We can't use more than 32 bits of hash in total, so that means that we require:
-     * (hashLog + 8) <= 32 && (chainLog + 8) <= 32
-     */
-    if (mode == ZSTD_cpm_createCDict && ZSTD_CDictIndicesAreTagged(&cPar)) {
-        U32 const maxShortCacheHashLog = 32 - ZSTD_SHORT_CACHE_TAG_BITS;
-        if (cPar.hashLog > maxShortCacheHashLog) {
-            cPar.hashLog = maxShortCacheHashLog;
-        }
-        if (cPar.chainLog > maxShortCacheHashLog) {
-            cPar.chainLog = maxShortCacheHashLog;
-        }
-    }
-
-
-    /* At this point, we aren't 100% sure if we are using the row match finder.
-     * Unless it is explicitly disabled, conservatively assume that it is enabled.
-     * In this case it will only be disabled for small sources, so shrinking the
-     * hash log a little bit shouldn't result in any ratio loss.
-     */
-    if (useRowMatchFinder == ZSTD_ps_auto)
-        useRowMatchFinder = ZSTD_ps_enable;
-
-    /* We can't hash more than 32-bits in total. So that means that we require:
-     * (hashLog - rowLog + 8) <= 32
-     */
-    if (ZSTD_rowMatchFinderUsed(cPar.strategy, useRowMatchFinder)) {
-        /* Switch to 32-entry rows if searchLog is 5 (or more) */
-        U32 const rowLog = BOUNDED(4, cPar.searchLog, 6);
-        U32 const maxRowHashLog = 32 - ZSTD_ROW_HASH_TAG_BITS;
-        U32 const maxHashLog = maxRowHashLog + rowLog;
-        assert(cPar.hashLog >= rowLog);
-        if (cPar.hashLog > maxHashLog) {
-            cPar.hashLog = maxHashLog;
-        }
-    }
-
-    return cPar;
+    /* The remaining adjustment logic is context-free and lives in Rust.  The
+     * short-cache and row-hash tag widths the leaf assumes are fixed
+     * private-header constants; keep them checked here. */
+    ZSTD_STATIC_ASSERT(ZSTD_SHORT_CACHE_TAG_BITS == 8);
+    ZSTD_STATIC_ASSERT(ZSTD_ROW_HASH_TAG_BITS == 8);
+    return ZSTD_rust_params_adjustCParams(cPar, (U64)srcSize, dictSize,
+                                          (int)mode, (int)useRowMatchFinder);
 }
 
 ZSTD_compressionParameters
@@ -1654,47 +1543,31 @@ ZSTD_sizeof_matchState(const ZSTD_compressionParameters* const cParams,
                        const int enableDedicatedDictSearch,
                        const U32 forCCtx)
 {
-    /* chain table size should be 0 for fast or row-hash strategies */
-    size_t const chainSize = ZSTD_allocateChainTable(cParams->strategy, useRowMatchFinder, enableDedicatedDictSearch && !forCCtx)
-                                ? ((size_t)1 << cParams->chainLog)
-                                : 0;
-    size_t const hSize = ((size_t)1) << cParams->hashLog;
-    U32    const hashLog3 = (forCCtx && cParams->minMatch==3) ? MIN(ZSTD_HASHLOG3_MAX, cParams->windowLog) : 0;
-    size_t const h3Size = hashLog3 ? ((size_t)1) << hashLog3 : 0;
-    /* We don't use ZSTD_cwksp_alloc_size() here because the tables aren't
-     * surrounded by redzones in ASAN. */
-    size_t const tableSpace = chainSize * sizeof(U32)
-                            + hSize * sizeof(U32)
-                            + h3Size * sizeof(U32);
-    size_t const optPotentialSpace =
-        ZSTD_cwksp_aligned64_alloc_size((MaxML+1) * sizeof(U32))
-      + ZSTD_cwksp_aligned64_alloc_size((MaxLL+1) * sizeof(U32))
-      + ZSTD_cwksp_aligned64_alloc_size((MaxOff+1) * sizeof(U32))
-      + ZSTD_cwksp_aligned64_alloc_size((1<<Litbits) * sizeof(U32))
-      + ZSTD_cwksp_aligned64_alloc_size(ZSTD_OPT_SIZE * sizeof(ZSTD_match_t))
-      + ZSTD_cwksp_aligned64_alloc_size(ZSTD_OPT_SIZE * sizeof(ZSTD_optimal_t));
-    size_t const lazyAdditionalSpace = ZSTD_rowMatchFinderUsed(cParams->strategy, useRowMatchFinder)
-                                            ? ZSTD_cwksp_aligned64_alloc_size(hSize)
-                                            : 0;
-    size_t const optSpace = (forCCtx && (cParams->strategy >= ZSTD_btopt))
-                                ? optPotentialSpace
-                                : 0;
-    size_t const slackSpace = ZSTD_cwksp_slack_space_required();
+    ZSTD_rustMatchStateSizing sizing;
+    sizing.hashLog3Max = ZSTD_HASHLOG3_MAX;
+    sizing.matchTSize = sizeof(ZSTD_match_t);
+    sizing.optimalTSize = sizeof(ZSTD_optimal_t);
+    sizing.asanRedzoneSize = ZSTD_RUST_ASAN_REDZONE_SIZE;
 
+    /* The Rust leaf hardcodes the frozen format bounds and workspace rules;
+     * keep them checked against the private headers here. */
+    ZSTD_STATIC_ASSERT(MaxML == 52 && MaxLL == 35 && MaxOff == 31);
+    ZSTD_STATIC_ASSERT(Litbits == 8 && ZSTD_OPT_SIZE == 4099);
+    ZSTD_STATIC_ASSERT(ZSTD_CWKSP_ALIGNMENT_BYTES == 64);
     /* tables are guaranteed to be sized in multiples of 64 bytes (or 16 uint32_t) */
     ZSTD_STATIC_ASSERT(ZSTD_HASHLOG_MIN >= 4 && ZSTD_WINDOWLOG_MIN >= 4 && ZSTD_CHAINLOG_MIN >= 4);
     assert(useRowMatchFinder != ZSTD_ps_auto);
 
-    DEBUGLOG(4, "chainSize: %u - hSize: %u - h3Size: %u",
-                (U32)chainSize, (U32)hSize, (U32)h3Size);
-    return tableSpace + optSpace + slackSpace + lazyAdditionalSpace;
+    return ZSTD_rust_params_estimateMatchStateSize(*cParams,
+                                                   (int)useRowMatchFinder,
+                                                   enableDedicatedDictSearch,
+                                                   forCCtx, &sizing);
 }
 
 /* Helper function for calculating memory requirements.
  * Gives a tighter bound than ZSTD_sequenceBound() by taking minMatch into account. */
 static size_t ZSTD_maxNbSeq(size_t blockSize, unsigned minMatch, int useSequenceProducer) {
-    U32 const divider = (minMatch==3 || useSequenceProducer) ? 3 : 4;
-    return blockSize / divider;
+    return ZSTD_rust_params_maxNbSeq(blockSize, minMatch, useSequenceProducer);
 }
 
 static size_t ZSTD_estimateCCtxSize_usingCCtxParams_internal(
@@ -5430,15 +5303,15 @@ size_t ZSTD_estimateCDictSize_advanced(
         size_t dictSize, ZSTD_compressionParameters cParams,
         ZSTD_dictLoadMethod_e dictLoadMethod)
 {
-    DEBUGLOG(5, "sizeof(ZSTD_CDict) : %u", (unsigned)sizeof(ZSTD_CDict));
-    return ZSTD_cwksp_alloc_size(sizeof(ZSTD_CDict))
-         + ZSTD_cwksp_alloc_size(HUF_WORKSPACE_SIZE)
-         /* enableDedicatedDictSearch == 1 ensures that CDict estimation will not be too small
-          * in case we are using DDS with row-hash. */
-         + ZSTD_sizeof_matchState(&cParams, ZSTD_resolveRowMatchFinderMode(ZSTD_ps_auto, &cParams),
-                                  /* enableDedicatedDictSearch */ 1, /* forCCtx */ 0)
-         + (dictLoadMethod == ZSTD_dlm_byRef ? 0
-            : ZSTD_cwksp_alloc_size(ZSTD_cwksp_align(dictSize, sizeof(void *))));
+    ZSTD_rustCDictSizing sizing;
+    sizing.cdictSize = sizeof(ZSTD_CDict);
+    sizing.hufWorkspaceSize = HUF_WORKSPACE_SIZE;
+    sizing.hashLog3Max = ZSTD_HASHLOG3_MAX;
+    sizing.matchTSize = sizeof(ZSTD_match_t);
+    sizing.optimalTSize = sizeof(ZSTD_optimal_t);
+    sizing.asanRedzoneSize = ZSTD_RUST_ASAN_REDZONE_SIZE;
+    return ZSTD_rust_params_estimateCDictSizeFromCParams(
+            dictSize, cParams, (int)dictLoadMethod, &sizing);
 }
 
 size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel)
@@ -7576,11 +7449,12 @@ size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output)
 
 
 /*-=====  Pre-defined compression levels  =====-*/
-#include "clevels.h"
+/* The compression-level tables (formerly included from clevels.h) live in
+ * rust/src/zstd_compress_params.rs. */
 
-int ZSTD_maxCLevel(void) { return ZSTD_MAX_CLEVEL; }
-int ZSTD_minCLevel(void) { return (int)-ZSTD_TARGETLENGTH_MAX; }
-int ZSTD_defaultCLevel(void) { return ZSTD_CLEVEL_DEFAULT; }
+int ZSTD_maxCLevel(void) { return ZSTD_rust_params_maxCLevel(); }
+int ZSTD_minCLevel(void) { return ZSTD_rust_params_minCLevel(); }
+int ZSTD_defaultCLevel(void) { return ZSTD_rust_params_defaultCLevel(); }
 
 static ZSTD_compressionParameters ZSTD_dedicatedDictSearch_getCParams(int const compressionLevel, size_t const dictSize)
 {
@@ -7639,26 +7513,6 @@ static void ZSTD_dedicatedDictSearch_revertCParams(
     }
 }
 
-static U64 ZSTD_getCParamRowSize(U64 srcSizeHint, size_t dictSize, ZSTD_CParamMode_e mode)
-{
-    switch (mode) {
-    case ZSTD_cpm_unknown:
-    case ZSTD_cpm_noAttachDict:
-    case ZSTD_cpm_createCDict:
-        break;
-    case ZSTD_cpm_attachDict:
-        dictSize = 0;
-        break;
-    default:
-        assert(0);
-        break;
-    }
-    {   int const unknown = srcSizeHint == ZSTD_CONTENTSIZE_UNKNOWN;
-        size_t const addedSize = unknown && dictSize > 0 ? 500 : 0;
-        return unknown && dictSize == 0 ? ZSTD_CONTENTSIZE_UNKNOWN : srcSizeHint+dictSize+addedSize;
-    }
-}
-
 /*! ZSTD_getCParams_internal() :
  * @return ZSTD_compressionParameters structure for a selected compression level, srcSize and dictSize.
  *  Note: srcSizeHint 0 means 0, use ZSTD_CONTENTSIZE_UNKNOWN for unknown.
@@ -7666,27 +7520,12 @@ static U64 ZSTD_getCParamRowSize(U64 srcSizeHint, size_t dictSize, ZSTD_CParamMo
  *  Note: `mode` controls how we treat the `dictSize`. See docs for `ZSTD_CParamMode_e`. */
 static ZSTD_compressionParameters ZSTD_getCParams_internal(int compressionLevel, unsigned long long srcSizeHint, size_t dictSize, ZSTD_CParamMode_e mode)
 {
-    U64 const rSize = ZSTD_getCParamRowSize(srcSizeHint, dictSize, mode);
-    U32 const tableID = (rSize <= 256 KB) + (rSize <= 128 KB) + (rSize <= 16 KB);
-    int row;
-    DEBUGLOG(5, "ZSTD_getCParams_internal (cLevel=%i)", compressionLevel);
-
-    /* row */
-    if (compressionLevel == 0) row = ZSTD_CLEVEL_DEFAULT;   /* 0 == default */
-    else if (compressionLevel < 0) row = 0;   /* entry 0 is baseline for fast mode */
-    else if (compressionLevel > ZSTD_MAX_CLEVEL) row = ZSTD_MAX_CLEVEL;
-    else row = compressionLevel;
-
-    {   ZSTD_compressionParameters cp = ZSTD_defaultCParameters[tableID][row];
-        DEBUGLOG(5, "ZSTD_getCParams_internal selected tableID: %u row: %u strat: %u", tableID, row, (U32)cp.strategy);
-        /* acceleration factor */
-        if (compressionLevel < 0) {
-            int const clampedCompressionLevel = MAX(ZSTD_minCLevel(), compressionLevel);
-            cp.targetLength = (unsigned)(-clampedCompressionLevel);
-        }
-        /* refine parameters based on srcSize & dictSize */
-        return ZSTD_adjustCParams_internal(cp, srcSizeHint, dictSize, mode, ZSTD_ps_auto);
-    }
+    /* Table selection is context-free and lives in Rust; the adjustment step
+     * stays behind ZSTD_adjustCParams_internal() so this build's strategy
+     * cascade applies. */
+    ZSTD_compressionParameters const cp = ZSTD_rust_params_selectCParams(
+            compressionLevel, srcSizeHint, dictSize, (int)mode);
+    return ZSTD_adjustCParams_internal(cp, srcSizeHint, dictSize, mode, ZSTD_ps_auto);
 }
 
 /*! ZSTD_getCParams() :
@@ -7705,13 +7544,9 @@ ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long l
 static ZSTD_parameters
 ZSTD_getParams_internal(int compressionLevel, unsigned long long srcSizeHint, size_t dictSize, ZSTD_CParamMode_e mode)
 {
-    ZSTD_parameters params;
     ZSTD_compressionParameters const cParams = ZSTD_getCParams_internal(compressionLevel, srcSizeHint, dictSize, mode);
     DEBUGLOG(5, "ZSTD_getParams (cLevel=%i)", compressionLevel);
-    ZSTD_memset(&params, 0, sizeof(params));
-    params.cParams = cParams;
-    params.fParams.contentSizeFlag = 1;
-    return params;
+    return ZSTD_rust_params_makeParams(cParams);
 }
 
 /*! ZSTD_getParams() :

rust/README.md

@@ -34,6 +34,12 @@ zstd ABI:
   - `zstd_compress_frame` serializes frame headers, skippable frames, and the
     last empty block; it takes scalar frame parameters so the C-owned
     `ZSTD_CCtx_params` layout never crosses the language boundary.
+  - `zstd_compress_params` owns the compression-level tables (formerly
+    `clevels.h`), parameter bounds, clamping, validation, table selection,
+    source/dictionary adjustment, and match-state/CDict size estimation.
+    The C integration layer keeps the public `ZSTD_*` symbols and feeds the
+    leaves configuration-owned scalars: the excluded-block-compressor
+    strategy cascade, struct sizes, and sanitizer redzone policy.
   - `zstd_fast` and `zstd_double_fast` implement the single- and two-table
     fast block match finders, including attached and external dictionary paths.
   - `zstd_lazy` implements greedy, lazy, lazy2, and binary-tree matching,

rust/src/lib.rs

@@ -28,6 +28,8 @@ pub mod zstd_compress_frame;
 #[cfg(feature = "compression")]
 pub mod zstd_compress_literals;
 #[cfg(feature = "compression")]
+pub mod zstd_compress_params;
+#[cfg(feature = "compression")]
 pub mod zstd_compress_sequences;
 #[cfg(feature = "compression")]
 pub mod zstd_compress_superblock;

rust/src/zstd_cli.rs

@@ -210,6 +210,7 @@ struct Cli {
     mmap_dict: i32,
     progress: i32,
     workers: Option<i32>,
+    single_thread: bool,
     block_size: Option<usize>,
     mem_limit: Option<u32>,
     ldm: bool,
@@ -254,6 +255,7 @@ impl Cli {
             mmap_dict: ZSTD_PS_AUTO,
             progress: FIO_PS_AUTO,
             workers: None,
+            single_thread: false,
             block_size: None,
             mem_limit: None,
             ldm: false,
@@ -332,8 +334,11 @@ unsafe fn default_worker_count() -> i32 {
 }
 
 #[cfg(feature = "compression")]
-unsafe fn resolved_worker_count(workers: Option<i32>) -> i32 {
+unsafe fn resolved_worker_count(workers: Option<i32>, single_thread: bool) -> i32 {
     match workers {
+        /* --single-thread pins zero workers; a bare zero (-T0 or the zstdmt
+         * program name) auto-detects the core count as in the C CLI. */
+        Some(0) if single_thread => 0,
         Some(0) => unsafe { UTIL_countPhysicalCores() }.max(1),
         Some(workers) => workers,
         None => unsafe { default_worker_count() },
@@ -385,7 +390,7 @@ fn usage(advanced: bool) {
         let _ = writeln!(out, "\nImplemented advanced compression controls:");
         let _ = writeln!(
             out,
-            "  --fast[=#], --ultra, --long[=#], --threads=#, --block-size=#"
+            "  --fast[=#], --ultra, --long[=#], --threads=#, --single-thread, --block-size=#"
         );
         let _ = writeln!(
             out,
@@ -638,6 +643,7 @@ fn parse_long_option(
                 | "--no-row-match-finder"
                 | "--row-match-finder"
                 | "--rsyncable"
+                | "--single-thread"
                 | "--compress-literals"
                 | "--no-compress-literals"
                 | "--exclude-compressed"
@@ -809,6 +815,14 @@ fn parse_long_option(
             cli.workers = Some(parse_worker_count(&value)?);
             Ok(None)
         }
+        "--single-thread" => {
+            /* As in the C CLI: zero workers plus a latch that suppresses the
+             * automatic core-count resolution, so fileio runs its
+             * single-thread streaming mode (slightly different from -T1). */
+            cli.workers = Some(0);
+            cli.single_thread = true;
+            Ok(None)
+        }
         "--memlimit" | "--memory" | "--memlimit-decompress" => {
             let value = next_value(attached, args, index, name)?;
             cli.mem_limit = Some(parse_u32(&value, "memory limit")?);
@@ -854,7 +868,6 @@ fn parse_long_option(
         | "--trace"
         | "--format"
         | "--priority"
-        | "--single-thread"
         | "--auto-threads"
         | "--fake-stdin-is-console"
         | "--fake-stdout-is-console"
@@ -1012,7 +1025,7 @@ unsafe fn apply_preferences(cli: &Cli, prefs: *mut FIO_prefs_t, ctx: *mut FIO_ct
                 }),
         );
         #[cfg(feature = "compression")]
-        FIO_setNbWorkers(prefs, resolved_worker_count(cli.workers));
+        FIO_setNbWorkers(prefs, resolved_worker_count(cli.workers, cli.single_thread));
         FIO_setLdmFlag(prefs, u32::from(cli.ldm));
         FIO_setAdaptiveMode(prefs, i32::from(cli.adapt));
         FIO_setRsyncable(prefs, i32::from(cli.rsyncable));
@@ -1502,6 +1515,36 @@ mod tests {
         let cli = parse(&["zstdmt", "input"]);
 
         assert_eq!(cli.workers, Some(0));
+        assert!(!cli.single_thread);
+    }
+
+    #[test]
+    fn single_thread_pins_zero_workers() {
+        let cli = parse(&["zstd", "--single-thread", "input"]);
+
+        assert_eq!(cli.workers, Some(0));
+        assert!(cli.single_thread);
+    }
+
+    #[test]
+    fn a_later_thread_count_overrides_single_thread_workers() {
+        /* Mirrors the C CLI: -T after --single-thread wins the worker count,
+         * while the single-thread latch stays set. */
+        let cli = parse(&["zstd", "--single-thread", "-T2", "input"]);
+
+        assert_eq!(cli.workers, Some(2));
+        assert!(cli.single_thread);
+    }
+
+    #[test]
+    fn single_thread_rejects_attached_values() {
+        let error = parse_args(vec![
+            OsString::from("zstd"),
+            OsString::from("--single-thread=1"),
+        ])
+        .expect_err("an attached value must not activate --single-thread");
+
+        assert!(error.contains("does not take an argument"));
     }
 
     #[test]

rust/src/zstd_compress_params.rs

@@ -0,0 +1,1048 @@
+#![allow(non_camel_case_types)]
+#![allow(non_snake_case)]
+#![allow(clippy::missing_safety_doc)]
+#![allow(clippy::too_many_arguments)]
+
+//! Context-free compression-parameter selection and sizing leaves.
+//!
+//! This module deliberately does **not** own the public `ZSTD_*` symbols yet.
+//! `zstd_compress.c` still owns configuration-sensitive policy: excluded block
+//! compressors, private `ZSTD_CCtx_params` layouts, LDM workspace sizing, and
+//! ASAN workspace policy.  The C integration layer can select a raw table
+//! entry here, apply its configured strategy cascade, then use the adjustment
+//! and sizing leaves below.  That keeps the Rust implementation independent of
+//! C preprocessor state while retaining byte-for-byte C policy for reduced
+//! builds.
+
+use crate::errors::{ZstdErrorCode, ERROR};
+use std::mem::size_of;
+use std::os::raw::c_int;
+
+pub const ZSTD_CONTENTSIZE_UNKNOWN: u64 = u64::MAX;
+
+const ZSTD_CLEVEL_DEFAULT: c_int = 3;
+const ZSTD_MAX_CLEVEL: c_int = 22;
+const ZSTD_TARGETLENGTH_MAX: c_int = 1 << 17;
+const ZSTD_BLOCKSIZE_MAX: usize = 1 << 17;
+
+const ZSTD_WINDOWLOG_MIN: c_int = 10;
+#[cfg(target_pointer_width = "32")]
+const ZSTD_WINDOWLOG_MAX: c_int = 30;
+#[cfg(not(target_pointer_width = "32"))]
+const ZSTD_WINDOWLOG_MAX: c_int = 31;
+const ZSTD_HASHLOG_MIN: c_int = 6;
+const ZSTD_HASHLOG_MAX: c_int = 30;
+const ZSTD_CHAINLOG_MIN: c_int = ZSTD_HASHLOG_MIN;
+#[cfg(target_pointer_width = "32")]
+const ZSTD_CHAINLOG_MAX: c_int = 29;
+#[cfg(not(target_pointer_width = "32"))]
+const ZSTD_CHAINLOG_MAX: c_int = 30;
+const ZSTD_SEARCHLOG_MIN: c_int = 1;
+const ZSTD_SEARCHLOG_MAX: c_int = ZSTD_WINDOWLOG_MAX - 1;
+const ZSTD_MINMATCH_MIN: c_int = 3;
+const ZSTD_MINMATCH_MAX: c_int = 7;
+const ZSTD_TARGETLENGTH_MIN: c_int = 0;
+
+const ZSTD_FAST: c_int = 1;
+const ZSTD_DFAST: c_int = 2;
+const ZSTD_GREEDY: c_int = 3;
+const ZSTD_LAZY: c_int = 4;
+const ZSTD_LAZY2: c_int = 5;
+const ZSTD_BTLAZY2: c_int = 6;
+const ZSTD_BTOPT: c_int = 7;
+const ZSTD_BTULTRA: c_int = 8;
+const ZSTD_BTULTRA2: c_int = 9;
+
+const ZSTD_C_COMPRESSION_LEVEL: c_int = 100;
+const ZSTD_C_WINDOW_LOG: c_int = 101;
+const ZSTD_C_HASH_LOG: c_int = 102;
+const ZSTD_C_CHAIN_LOG: c_int = 103;
+const ZSTD_C_SEARCH_LOG: c_int = 104;
+const ZSTD_C_MIN_MATCH: c_int = 105;
+const ZSTD_C_TARGET_LENGTH: c_int = 106;
+const ZSTD_C_STRATEGY: c_int = 107;
+
+/// Private compression-parameter modes from `zstd_compress_internal.h`.
+///
+/// They are ABI-compatible with `ZSTD_CParamMode_e` and intentionally kept as
+/// integer constants because that enum remains private C API for now.
+pub const ZSTD_RUST_CPM_NO_ATTACH_DICT: c_int = 0;
+pub const ZSTD_RUST_CPM_ATTACH_DICT: c_int = 1;
+pub const ZSTD_RUST_CPM_CREATE_CDICT: c_int = 2;
+pub const ZSTD_RUST_CPM_UNKNOWN: c_int = 3;
+
+/// `ZSTD_ParamSwitch_e` values used by the adjustment and sizing leaves.
+pub const ZSTD_RUST_PS_AUTO: c_int = 0;
+pub const ZSTD_RUST_PS_ENABLE: c_int = 1;
+pub const ZSTD_RUST_PS_DISABLE: c_int = 2;
+
+/// ABI-compatible `ZSTD_compressionParameters` from `zstd.h`.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub struct ZSTD_compressionParameters {
+    pub windowLog: u32,
+    pub chainLog: u32,
+    pub hashLog: u32,
+    pub searchLog: u32,
+    pub minMatch: u32,
+    pub targetLength: u32,
+    pub strategy: c_int,
+}
+
+/// ABI-compatible `ZSTD_frameParameters` from `zstd.h`.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub struct ZSTD_frameParameters {
+    pub contentSizeFlag: c_int,
+    pub checksumFlag: c_int,
+    pub noDictIDFlag: c_int,
+}
+
+/// ABI-compatible `ZSTD_parameters` from `zstd.h`.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub struct ZSTD_parameters {
+    pub cParams: ZSTD_compressionParameters,
+    pub fParams: ZSTD_frameParameters,
+}
+
+/// ABI-compatible `ZSTD_bounds` from `zstd.h`.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub struct ZSTD_bounds {
+    pub error: usize,
+    pub lowerBound: c_int,
+    pub upperBound: c_int,
+}
+
+/* `clevels.h`, represented as raw fields so the table stays compact and easy
+ * to compare mechanically against its C source.  Field order is W, C, H, S,
+ * L, TL, strategy. */
+const DEFAULT_CPARAMS: [[[u32; 7]; 23]; 4] = [
+    [
+        [19, 12, 13, 1, 6, 1, ZSTD_FAST as u32],
+        [19, 13, 14, 1, 7, 0, ZSTD_FAST as u32],
+        [20, 15, 16, 1, 6, 0, ZSTD_FAST as u32],
+        [21, 16, 17, 1, 5, 0, ZSTD_DFAST as u32],
+        [21, 18, 18, 1, 5, 0, ZSTD_DFAST as u32],
+        [21, 18, 19, 3, 5, 2, ZSTD_GREEDY as u32],
+        [21, 18, 19, 3, 5, 4, ZSTD_LAZY as u32],
+        [21, 19, 20, 4, 5, 8, ZSTD_LAZY as u32],
+        [21, 19, 20, 4, 5, 16, ZSTD_LAZY2 as u32],
+        [22, 20, 21, 4, 5, 16, ZSTD_LAZY2 as u32],
+        [22, 21, 22, 5, 5, 16, ZSTD_LAZY2 as u32],
+        [22, 21, 22, 6, 5, 16, ZSTD_LAZY2 as u32],
+        [22, 22, 23, 6, 5, 32, ZSTD_LAZY2 as u32],
+        [22, 22, 22, 4, 5, 32, ZSTD_BTLAZY2 as u32],
+        [22, 22, 23, 5, 5, 32, ZSTD_BTLAZY2 as u32],
+        [22, 23, 23, 6, 5, 32, ZSTD_BTLAZY2 as u32],
+        [22, 22, 22, 5, 5, 48, ZSTD_BTOPT as u32],
+        [23, 23, 22, 5, 4, 64, ZSTD_BTOPT as u32],
+        [23, 23, 22, 6, 3, 64, ZSTD_BTULTRA as u32],
+        [23, 24, 22, 7, 3, 256, ZSTD_BTULTRA2 as u32],
+        [25, 25, 23, 7, 3, 256, ZSTD_BTULTRA2 as u32],
+        [26, 26, 24, 7, 3, 512, ZSTD_BTULTRA2 as u32],
+        [27, 27, 25, 9, 3, 999, ZSTD_BTULTRA2 as u32],
+    ],
+    [
+        [18, 12, 13, 1, 5, 1, ZSTD_FAST as u32],
+        [18, 13, 14, 1, 6, 0, ZSTD_FAST as u32],
+        [18, 14, 14, 1, 5, 0, ZSTD_DFAST as u32],
+        [18, 16, 16, 1, 4, 0, ZSTD_DFAST as u32],
+        [18, 16, 17, 3, 5, 2, ZSTD_GREEDY as u32],
+        [18, 17, 18, 5, 5, 2, ZSTD_GREEDY as u32],
+        [18, 18, 19, 3, 5, 4, ZSTD_LAZY as u32],
+        [18, 18, 19, 4, 4, 4, ZSTD_LAZY as u32],
+        [18, 18, 19, 4, 4, 8, ZSTD_LAZY2 as u32],
+        [18, 18, 19, 5, 4, 8, ZSTD_LAZY2 as u32],
+        [18, 18, 19, 6, 4, 8, ZSTD_LAZY2 as u32],
+        [18, 18, 19, 5, 4, 12, ZSTD_BTLAZY2 as u32],
+        [18, 19, 19, 7, 4, 12, ZSTD_BTLAZY2 as u32],
+        [18, 18, 19, 4, 4, 16, ZSTD_BTOPT as u32],
+        [18, 18, 19, 4, 3, 32, ZSTD_BTOPT as u32],
+        [18, 18, 19, 6, 3, 128, ZSTD_BTOPT as u32],
+        [18, 19, 19, 6, 3, 128, ZSTD_BTULTRA as u32],
+        [18, 19, 19, 8, 3, 256, ZSTD_BTULTRA as u32],
+        [18, 19, 19, 6, 3, 128, ZSTD_BTULTRA2 as u32],
+        [18, 19, 19, 8, 3, 256, ZSTD_BTULTRA2 as u32],
+        [18, 19, 19, 10, 3, 512, ZSTD_BTULTRA2 as u32],
+        [18, 19, 19, 12, 3, 512, ZSTD_BTULTRA2 as u32],
+        [18, 19, 19, 13, 3, 999, ZSTD_BTULTRA2 as u32],
+    ],
+    [
+        [17, 12, 12, 1, 5, 1, ZSTD_FAST as u32],
+        [17, 12, 13, 1, 6, 0, ZSTD_FAST as u32],
+        [17, 13, 15, 1, 5, 0, ZSTD_FAST as u32],
+        [17, 15, 16, 2, 5, 0, ZSTD_DFAST as u32],
+        [17, 17, 17, 2, 4, 0, ZSTD_DFAST as u32],
+        [17, 16, 17, 3, 4, 2, ZSTD_GREEDY as u32],
+        [17, 16, 17, 3, 4, 4, ZSTD_LAZY as u32],
+        [17, 16, 17, 3, 4, 8, ZSTD_LAZY2 as u32],
+        [17, 16, 17, 4, 4, 8, ZSTD_LAZY2 as u32],
+        [17, 16, 17, 5, 4, 8, ZSTD_LAZY2 as u32],
+        [17, 16, 17, 6, 4, 8, ZSTD_LAZY2 as u32],
+        [17, 17, 17, 5, 4, 8, ZSTD_BTLAZY2 as u32],
+        [17, 18, 17, 7, 4, 12, ZSTD_BTLAZY2 as u32],
+        [17, 18, 17, 3, 4, 12, ZSTD_BTOPT as u32],
+        [17, 18, 17, 4, 3, 32, ZSTD_BTOPT as u32],
+        [17, 18, 17, 6, 3, 256, ZSTD_BTOPT as u32],
+        [17, 18, 17, 6, 3, 128, ZSTD_BTULTRA as u32],
+        [17, 18, 17, 8, 3, 256, ZSTD_BTULTRA as u32],
+        [17, 18, 17, 10, 3, 512, ZSTD_BTULTRA as u32],
+        [17, 18, 17, 5, 3, 256, ZSTD_BTULTRA2 as u32],
+        [17, 18, 17, 7, 3, 512, ZSTD_BTULTRA2 as u32],
+        [17, 18, 17, 9, 3, 512, ZSTD_BTULTRA2 as u32],
+        [17, 18, 17, 11, 3, 999, ZSTD_BTULTRA2 as u32],
+    ],
+    [
+        [14, 12, 13, 1, 5, 1, ZSTD_FAST as u32],
+        [14, 14, 15, 1, 5, 0, ZSTD_FAST as u32],
+        [14, 14, 15, 1, 4, 0, ZSTD_FAST as u32],
+        [14, 14, 15, 2, 4, 0, ZSTD_DFAST as u32],
+        [14, 14, 14, 4, 4, 2, ZSTD_GREEDY as u32],
+        [14, 14, 14, 3, 4, 4, ZSTD_LAZY as u32],
+        [14, 14, 14, 4, 4, 8, ZSTD_LAZY2 as u32],
+        [14, 14, 14, 6, 4, 8, ZSTD_LAZY2 as u32],
+        [14, 14, 14, 8, 4, 8, ZSTD_LAZY2 as u32],
+        [14, 15, 14, 5, 4, 8, ZSTD_BTLAZY2 as u32],
+        [14, 15, 14, 9, 4, 8, ZSTD_BTLAZY2 as u32],
+        [14, 15, 14, 3, 4, 12, ZSTD_BTOPT as u32],
+        [14, 15, 14, 4, 3, 24, ZSTD_BTOPT as u32],
+        [14, 15, 14, 5, 3, 32, ZSTD_BTULTRA as u32],
+        [14, 15, 15, 6, 3, 64, ZSTD_BTULTRA as u32],
+        [14, 15, 15, 7, 3, 256, ZSTD_BTULTRA as u32],
+        [14, 15, 15, 5, 3, 48, ZSTD_BTULTRA2 as u32],
+        [14, 15, 15, 6, 3, 128, ZSTD_BTULTRA2 as u32],
+        [14, 15, 15, 7, 3, 256, ZSTD_BTULTRA2 as u32],
+        [14, 15, 15, 8, 3, 256, ZSTD_BTULTRA2 as u32],
+        [14, 15, 15, 8, 3, 512, ZSTD_BTULTRA2 as u32],
+        [14, 15, 15, 9, 3, 512, ZSTD_BTULTRA2 as u32],
+        [14, 15, 15, 10, 3, 999, ZSTD_BTULTRA2 as u32],
+    ],
+];
+
+#[inline]
+fn cparams_from_row(row: [u32; 7]) -> ZSTD_compressionParameters {
+    ZSTD_compressionParameters {
+        windowLog: row[0],
+        chainLog: row[1],
+        hashLog: row[2],
+        searchLog: row[3],
+        minMatch: row[4],
+        targetLength: row[5],
+        strategy: row[6] as c_int,
+    }
+}
+
+#[inline]
+fn bounds(param: c_int) -> ZSTD_bounds {
+    let (lowerBound, upperBound) = match param {
+        ZSTD_C_COMPRESSION_LEVEL => (ZSTD_rust_params_minCLevel(), ZSTD_rust_params_maxCLevel()),
+        ZSTD_C_WINDOW_LOG => (ZSTD_WINDOWLOG_MIN, ZSTD_WINDOWLOG_MAX),
+        ZSTD_C_HASH_LOG => (ZSTD_HASHLOG_MIN, ZSTD_HASHLOG_MAX),
+        ZSTD_C_CHAIN_LOG => (ZSTD_CHAINLOG_MIN, ZSTD_CHAINLOG_MAX),
+        ZSTD_C_SEARCH_LOG => (ZSTD_SEARCHLOG_MIN, ZSTD_SEARCHLOG_MAX),
+        ZSTD_C_MIN_MATCH => (ZSTD_MINMATCH_MIN, ZSTD_MINMATCH_MAX),
+        ZSTD_C_TARGET_LENGTH => (ZSTD_TARGETLENGTH_MIN, ZSTD_TARGETLENGTH_MAX),
+        ZSTD_C_STRATEGY => (ZSTD_FAST, ZSTD_BTULTRA2),
+        _ => {
+            return ZSTD_bounds {
+                error: ERROR(ZstdErrorCode::ParameterUnsupported),
+                lowerBound: 0,
+                upperBound: 0,
+            }
+        }
+    };
+    ZSTD_bounds {
+        error: 0,
+        lowerBound,
+        upperBound,
+    }
+}
+
+#[inline]
+fn within_bounds(param: c_int, value: c_int) -> bool {
+    let bounds = bounds(param);
+    bounds.error == 0 && value >= bounds.lowerBound && value <= bounds.upperBound
+}
+
+#[inline]
+fn clamp_unsigned(value: u32, param: c_int) -> u32 {
+    let bounds = bounds(param);
+    debug_assert_eq!(bounds.error, 0);
+    let signed = value as c_int;
+    if signed < bounds.lowerBound {
+        bounds.lowerBound as u32
+    } else if signed > bounds.upperBound {
+        bounds.upperBound as u32
+    } else {
+        value
+    }
+}
+
+#[inline]
+fn clamp_cparams(mut cparams: ZSTD_compressionParameters) -> ZSTD_compressionParameters {
+    cparams.windowLog = clamp_unsigned(cparams.windowLog, ZSTD_C_WINDOW_LOG);
+    cparams.chainLog = clamp_unsigned(cparams.chainLog, ZSTD_C_CHAIN_LOG);
+    cparams.hashLog = clamp_unsigned(cparams.hashLog, ZSTD_C_HASH_LOG);
+    cparams.searchLog = clamp_unsigned(cparams.searchLog, ZSTD_C_SEARCH_LOG);
+    cparams.minMatch = clamp_unsigned(cparams.minMatch, ZSTD_C_MIN_MATCH);
+    cparams.targetLength = clamp_unsigned(cparams.targetLength, ZSTD_C_TARGET_LENGTH);
+    let strategy_bounds = bounds(ZSTD_C_STRATEGY);
+    if cparams.strategy < strategy_bounds.lowerBound {
+        cparams.strategy = strategy_bounds.lowerBound;
+    } else if cparams.strategy > strategy_bounds.upperBound {
+        cparams.strategy = strategy_bounds.upperBound;
+    }
+    cparams
+}
+
+#[inline]
+fn highbit32(value: u32) -> u32 {
+    debug_assert_ne!(value, 0);
+    u32::BITS - 1 - value.leading_zeros()
+}
+
+#[inline]
+fn cycle_log(hash_log: u32, strategy: c_int) -> u32 {
+    hash_log.wrapping_sub((strategy >= ZSTD_BTLAZY2) as u32)
+}
+
+#[inline]
+fn strategy_supports_row_match_finder(strategy: c_int) -> bool {
+    (ZSTD_GREEDY..=ZSTD_LAZY2).contains(&strategy)
+}
+
+#[inline]
+fn row_match_finder_used(strategy: c_int, mode: c_int) -> bool {
+    debug_assert_ne!(mode, ZSTD_RUST_PS_AUTO);
+    strategy_supports_row_match_finder(strategy) && mode == ZSTD_RUST_PS_ENABLE
+}
+
+#[inline]
+fn resolve_row_match_finder(mode: c_int, cparams: ZSTD_compressionParameters) -> c_int {
+    if mode != ZSTD_RUST_PS_AUTO {
+        return mode;
+    }
+    if strategy_supports_row_match_finder(cparams.strategy) && cparams.windowLog > 14 {
+        ZSTD_RUST_PS_ENABLE
+    } else {
+        ZSTD_RUST_PS_DISABLE
+    }
+}
+
+#[inline]
+fn dict_and_window_log(window_log: u32, src_size: u64, dict_size: u64) -> u32 {
+    /* 1ULL << ZSTD_WINDOWLOG_MAX, which is smaller for 32-bit builds. */
+    const MAX_WINDOW_SIZE: u64 = 1u64 << ZSTD_WINDOWLOG_MAX;
+    if dict_size == 0 {
+        return window_log;
+    }
+    debug_assert!(window_log <= ZSTD_WINDOWLOG_MAX as u32);
+    debug_assert_ne!(src_size, ZSTD_CONTENTSIZE_UNKNOWN);
+    let window_size = 1u64 << window_log;
+    if window_size >= dict_size.wrapping_add(src_size) {
+        window_log
+    } else {
+        let dict_and_window_size = dict_size.wrapping_add(window_size);
+        if dict_and_window_size >= MAX_WINDOW_SIZE {
+            ZSTD_WINDOWLOG_MAX as u32
+        } else {
+            highbit32((dict_and_window_size as u32).wrapping_sub(1)) + 1
+        }
+    }
+}
+
+/// Adjusts a *validated, configuration-resolved* parameter set.
+///
+/// This is the direct Rust leaf for `ZSTD_adjustCParams_internal()` after the
+/// C wrapper has applied its `ZSTD_EXCLUDE_*_BLOCK_COMPRESSOR` cascade.  In
+/// particular, it does not select a fallback strategy itself. `srcSize == 0`
+/// means a known empty input here, just as it does in the C internal helper;
+/// the public C wrapper must translate zero to `ZSTD_CONTENTSIZE_UNKNOWN`.
+fn adjust_cparams(
+    mut cparams: ZSTD_compressionParameters,
+    mut src_size: u64,
+    mut dict_size: usize,
+    mode: c_int,
+    mut use_row_match_finder: c_int,
+) -> ZSTD_compressionParameters {
+    debug_assert_eq!(check_cparams(cparams), 0);
+
+    const MIN_SRC_SIZE: u64 = 513;
+    /* 1ULL << (ZSTD_WINDOWLOG_MAX - 1), which is smaller for 32-bit builds. */
+    const MAX_WINDOW_RESIZE: u64 = 1u64 << (ZSTD_WINDOWLOG_MAX - 1);
+
+    match mode {
+        ZSTD_RUST_CPM_UNKNOWN | ZSTD_RUST_CPM_NO_ATTACH_DICT => {}
+        ZSTD_RUST_CPM_CREATE_CDICT => {
+            if dict_size != 0 && src_size == ZSTD_CONTENTSIZE_UNKNOWN {
+                src_size = MIN_SRC_SIZE;
+            }
+        }
+        ZSTD_RUST_CPM_ATTACH_DICT => dict_size = 0,
+        _ => debug_assert!(false, "invalid ZSTD_CParamMode_e"),
+    }
+
+    if src_size <= MAX_WINDOW_RESIZE && (dict_size as u64) <= MAX_WINDOW_RESIZE {
+        let total_size = src_size.wrapping_add(dict_size as u64) as u32;
+        let hash_size_min = 1u32 << ZSTD_HASHLOG_MIN;
+        let src_log = if total_size < hash_size_min {
+            ZSTD_HASHLOG_MIN as u32
+        } else {
+            highbit32(total_size.wrapping_sub(1)) + 1
+        };
+        cparams.windowLog = cparams.windowLog.min(src_log);
+    }
+
+    if src_size != ZSTD_CONTENTSIZE_UNKNOWN {
+        let dict_and_window_log =
+            dict_and_window_log(cparams.windowLog, src_size, dict_size as u64);
+        let cycle_log = cycle_log(cparams.chainLog, cparams.strategy);
+        cparams.hashLog = cparams.hashLog.min(dict_and_window_log + 1);
+        if cycle_log > dict_and_window_log {
+            cparams.chainLog = cparams
+                .chainLog
+                .wrapping_sub(cycle_log - dict_and_window_log);
+        }
+    }
+
+    cparams.windowLog = cparams.windowLog.max(ZSTD_WINDOWLOG_MIN as u32);
+
+    /* The short-cache tags used for fast and dfast CDicts consume eight bits
+     * of each 32-bit index.  This is a fixed private-header constant today;
+     * if it becomes configurable, the C shim must pass it as an explicit
+     * adjustment input rather than silently changing this leaf. */
+    if mode == ZSTD_RUST_CPM_CREATE_CDICT
+        && (cparams.strategy == ZSTD_FAST || cparams.strategy == ZSTD_DFAST)
+    {
+        const SHORT_CACHE_TAG_BITS: u32 = 8;
+        let max_short_cache_hash_log = 32 - SHORT_CACHE_TAG_BITS;
+        cparams.hashLog = cparams.hashLog.min(max_short_cache_hash_log);
+        cparams.chainLog = cparams.chainLog.min(max_short_cache_hash_log);
+    }
+
+    if use_row_match_finder == ZSTD_RUST_PS_AUTO {
+        use_row_match_finder = ZSTD_RUST_PS_ENABLE;
+    }
+    if row_match_finder_used(cparams.strategy, use_row_match_finder) {
+        const ROW_HASH_TAG_BITS: u32 = 8;
+        let row_log = cparams.searchLog.clamp(4, 6);
+        let max_hash_log = (32 - ROW_HASH_TAG_BITS) + row_log;
+        debug_assert!(cparams.hashLog >= row_log);
+        cparams.hashLog = cparams.hashLog.min(max_hash_log);
+    }
+
+    cparams
+}
+
+#[inline]
+fn get_cparam_row_size(src_size_hint: u64, dict_size: usize, mode: c_int) -> u64 {
+    let mut dict_size = dict_size as u64;
+    match mode {
+        ZSTD_RUST_CPM_UNKNOWN | ZSTD_RUST_CPM_NO_ATTACH_DICT | ZSTD_RUST_CPM_CREATE_CDICT => {}
+        ZSTD_RUST_CPM_ATTACH_DICT => dict_size = 0,
+        _ => debug_assert!(false, "invalid ZSTD_CParamMode_e"),
+    }
+    let unknown = src_size_hint == ZSTD_CONTENTSIZE_UNKNOWN;
+    let added_size = if unknown && dict_size > 0 { 500 } else { 0 };
+    if unknown && dict_size == 0 {
+        ZSTD_CONTENTSIZE_UNKNOWN
+    } else {
+        src_size_hint
+            .wrapping_add(dict_size)
+            .wrapping_add(added_size)
+    }
+}
+
+/// Selects a raw compression-level-table entry, without strategy cascading or
+/// source/dictionary adjustment.
+///
+/// A C wrapper must apply its active excluded-compressor cascade to the
+/// returned strategy before calling [`ZSTD_rust_params_adjustCParams`].
+fn select_cparams(
+    compression_level: c_int,
+    src_size_hint: u64,
+    dict_size: usize,
+    mode: c_int,
+) -> ZSTD_compressionParameters {
+    let row_size = get_cparam_row_size(src_size_hint, dict_size, mode);
+    let table_id = usize::from(row_size <= 256 * 1024)
+        + usize::from(row_size <= 128 * 1024)
+        + usize::from(row_size <= 16 * 1024);
+    let row = if compression_level == 0 {
+        ZSTD_CLEVEL_DEFAULT
+    } else if compression_level < 0 {
+        0
+    } else {
+        compression_level.min(ZSTD_MAX_CLEVEL)
+    } as usize;
+
+    let mut cparams = cparams_from_row(DEFAULT_CPARAMS[table_id][row]);
+    if compression_level < 0 {
+        let clamped = compression_level.max(ZSTD_rust_params_minCLevel());
+        cparams.targetLength = (-clamped) as u32;
+    }
+    cparams
+}
+
+#[inline]
+fn make_params(cparams: ZSTD_compressionParameters) -> ZSTD_parameters {
+    ZSTD_parameters {
+        cParams: cparams,
+        fParams: ZSTD_frameParameters {
+            contentSizeFlag: 1,
+            checksumFlag: 0,
+            noDictIDFlag: 0,
+        },
+    }
+}
+
+#[inline]
+fn check_cparams(cparams: ZSTD_compressionParameters) -> usize {
+    if !within_bounds(ZSTD_C_WINDOW_LOG, cparams.windowLog as c_int)
+        || !within_bounds(ZSTD_C_CHAIN_LOG, cparams.chainLog as c_int)
+        || !within_bounds(ZSTD_C_HASH_LOG, cparams.hashLog as c_int)
+        || !within_bounds(ZSTD_C_SEARCH_LOG, cparams.searchLog as c_int)
+        || !within_bounds(ZSTD_C_MIN_MATCH, cparams.minMatch as c_int)
+        || !within_bounds(ZSTD_C_TARGET_LENGTH, cparams.targetLength as c_int)
+        || !within_bounds(ZSTD_C_STRATEGY, cparams.strategy)
+    {
+        ERROR(ZstdErrorCode::ParameterOutOfBound)
+    } else {
+        0
+    }
+}
+
+/// Returns the highest table-backed compression level (`ZSTD_MAX_CLEVEL`).
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_maxCLevel() -> c_int {
+    ZSTD_MAX_CLEVEL
+}
+
+/// Returns the lowest public fast level (`-ZSTD_TARGETLENGTH_MAX`).
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_minCLevel() -> c_int {
+    -ZSTD_TARGETLENGTH_MAX
+}
+
+/// Returns the default compression level from `zstd.h`.
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_defaultCLevel() -> c_int {
+    ZSTD_CLEVEL_DEFAULT
+}
+
+/// Returns bounds for the seven core compression parameters and compression
+/// level.  Other `ZSTD_cParameter` cases remain C-owned.
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_getBounds(param: c_int) -> ZSTD_bounds {
+    bounds(param)
+}
+
+/// Checks the seven fields of `ZSTD_compressionParameters`.
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_checkCParams(cparams: ZSTD_compressionParameters) -> usize {
+    check_cparams(cparams)
+}
+
+/// Clamps the seven fields of `ZSTD_compressionParameters` to public bounds.
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_clampCParams(
+    cparams: ZSTD_compressionParameters,
+) -> ZSTD_compressionParameters {
+    clamp_cparams(cparams)
+}
+
+/// C ABI for `ZSTD_cycleLog()`.
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_cycleLog(hashLog: u32, strategy: c_int) -> u32 {
+    cycle_log(hashLog, strategy)
+}
+
+/// C ABI for private `ZSTD_getCParamRowSize()`.
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_getCParamRowSize(
+    srcSizeHint: u64,
+    dictSize: usize,
+    mode: c_int,
+) -> u64 {
+    get_cparam_row_size(srcSizeHint, dictSize, mode)
+}
+
+/// Returns the unadjusted compression-level-table entry.
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_selectCParams(
+    compressionLevel: c_int,
+    srcSizeHint: u64,
+    dictSize: usize,
+    mode: c_int,
+) -> ZSTD_compressionParameters {
+    select_cparams(compressionLevel, srcSizeHint, dictSize, mode)
+}
+
+/// Adjusts a validated, strategy-resolved C parameter set.
+///
+/// See [`adjust_cparams`] for the required C-side policy step.
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_adjustCParams(
+    cparams: ZSTD_compressionParameters,
+    srcSize: u64,
+    dictSize: usize,
+    mode: c_int,
+    useRowMatchFinder: c_int,
+) -> ZSTD_compressionParameters {
+    adjust_cparams(cparams, srcSize, dictSize, mode, useRowMatchFinder)
+}
+
+/// Builds `ZSTD_parameters` with the public default frame parameters.
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_makeParams(
+    cparams: ZSTD_compressionParameters,
+) -> ZSTD_parameters {
+    make_params(cparams)
+}
+
+/// Runtime sizes needed to reproduce `ZSTD_sizeof_matchState()` without
+/// exposing private C structures to Rust.
+///
+/// `asanRedzoneSize` is `ZSTD_CWKSP_ASAN_REDZONE_SIZE` when workspace
+/// poisoning is enabled and zero otherwise. `matchTSize` and `optimalTSize`
+/// must be `sizeof(ZSTD_match_t)` and `sizeof(ZSTD_optimal_t)` respectively.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default)]
+pub struct ZSTD_rustMatchStateSizing {
+    pub hashLog3Max: u32,
+    pub matchTSize: usize,
+    pub optimalTSize: usize,
+    pub asanRedzoneSize: usize,
+}
+
+/// C-only layout inputs for `ZSTD_estimateCDictSize_advanced()`.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default)]
+pub struct ZSTD_rustCDictSizing {
+    pub cdictSize: usize,
+    pub hufWorkspaceSize: usize,
+    pub hashLog3Max: u32,
+    pub matchTSize: usize,
+    pub optimalTSize: usize,
+    pub asanRedzoneSize: usize,
+}
+
+#[inline]
+fn cwksp_alloc_size(size: usize, asan_redzone_size: usize) -> usize {
+    if size == 0 {
+        0
+    } else {
+        size.wrapping_add(asan_redzone_size.wrapping_mul(2))
+    }
+}
+
+#[inline]
+fn cwksp_align(size: usize, alignment: usize) -> usize {
+    debug_assert!(alignment.is_power_of_two());
+    size.wrapping_add(alignment - 1) & !(alignment - 1)
+}
+
+#[inline]
+fn cwksp_aligned64_alloc_size(size: usize, asan_redzone_size: usize) -> usize {
+    cwksp_alloc_size(cwksp_align(size, 64), asan_redzone_size)
+}
+
+#[inline]
+fn shift_size(log: u32) -> usize {
+    debug_assert!(log < usize::BITS);
+    1usize << log
+}
+
+#[inline]
+fn allocate_chain_table(strategy: c_int, use_row_match_finder: c_int, for_dds_dict: bool) -> bool {
+    for_dds_dict
+        || (strategy != ZSTD_FAST && !row_match_finder_used(strategy, use_row_match_finder))
+}
+
+fn estimate_match_state_size(
+    cparams: ZSTD_compressionParameters,
+    use_row_match_finder: c_int,
+    enable_dedicated_dict_search: bool,
+    for_cctx: bool,
+    sizing: ZSTD_rustMatchStateSizing,
+) -> usize {
+    if check_cparams(cparams) != 0 || use_row_match_finder == ZSTD_RUST_PS_AUTO {
+        return 0;
+    }
+
+    let chain_size = if allocate_chain_table(
+        cparams.strategy,
+        use_row_match_finder,
+        enable_dedicated_dict_search && !for_cctx,
+    ) {
+        shift_size(cparams.chainLog)
+    } else {
+        0
+    };
+    let hash_size = shift_size(cparams.hashLog);
+    let hash_log_3 = if for_cctx && cparams.minMatch == 3 {
+        cparams.windowLog.min(sizing.hashLog3Max)
+    } else {
+        0
+    };
+    let hash3_size = if hash_log_3 == 0 {
+        0
+    } else {
+        shift_size(hash_log_3)
+    };
+    let table_space = chain_size
+        .wrapping_mul(size_of::<u32>())
+        .wrapping_add(hash_size.wrapping_mul(size_of::<u32>()))
+        .wrapping_add(hash3_size.wrapping_mul(size_of::<u32>()));
+
+    let redzone = sizing.asanRedzoneSize;
+    let opt_potential_space = cwksp_aligned64_alloc_size((52 + 1) * size_of::<u32>(), redzone)
+        .wrapping_add(cwksp_aligned64_alloc_size(
+            (35 + 1) * size_of::<u32>(),
+            redzone,
+        ))
+        .wrapping_add(cwksp_aligned64_alloc_size(
+            (31 + 1) * size_of::<u32>(),
+            redzone,
+        ))
+        .wrapping_add(cwksp_aligned64_alloc_size(
+            (1 << 8) * size_of::<u32>(),
+            redzone,
+        ))
+        .wrapping_add(cwksp_aligned64_alloc_size(
+            4099usize.wrapping_mul(sizing.matchTSize),
+            redzone,
+        ))
+        .wrapping_add(cwksp_aligned64_alloc_size(
+            4099usize.wrapping_mul(sizing.optimalTSize),
+            redzone,
+        ));
+    let lazy_additional_space = if row_match_finder_used(cparams.strategy, use_row_match_finder) {
+        cwksp_aligned64_alloc_size(hash_size, redzone)
+    } else {
+        0
+    };
+    let opt_space = if for_cctx && cparams.strategy >= ZSTD_BTOPT {
+        opt_potential_space
+    } else {
+        0
+    };
+    let slack_space = 2 * 64;
+
+    table_space
+        .wrapping_add(opt_space)
+        .wrapping_add(slack_space)
+        .wrapping_add(lazy_additional_space)
+}
+
+/// Pure leaf for private `ZSTD_sizeof_matchState()`.
+///
+/// `useRowMatchFinder` must already be resolved to enable or disable.  A NULL
+/// `sizing` pointer or invalid C parameters returns zero; C never supplies
+/// either in a valid estimator call.
+#[no_mangle]
+pub unsafe extern "C" fn ZSTD_rust_params_estimateMatchStateSize(
+    cparams: ZSTD_compressionParameters,
+    useRowMatchFinder: c_int,
+    enableDedicatedDictSearch: c_int,
+    forCCtx: u32,
+    sizing: *const ZSTD_rustMatchStateSizing,
+) -> usize {
+    if sizing.is_null() {
+        return 0;
+    }
+    let sizing = unsafe { *sizing };
+    estimate_match_state_size(
+        cparams,
+        useRowMatchFinder,
+        enableDedicatedDictSearch != 0,
+        forCCtx != 0,
+        sizing,
+    )
+}
+
+#[inline]
+fn max_nb_seq(block_size: usize, min_match: u32, use_sequence_producer: bool) -> usize {
+    let divider = if min_match == 3 || use_sequence_producer {
+        3
+    } else {
+        4
+    };
+    block_size / divider
+}
+
+/// Pure leaf for private `ZSTD_maxNbSeq()`.
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_maxNbSeq(
+    blockSize: usize,
+    minMatch: u32,
+    useSequenceProducer: c_int,
+) -> usize {
+    max_nb_seq(blockSize, minMatch, useSequenceProducer != 0)
+}
+
+/// Pure leaf for private `ZSTD_resolveMaxBlockSize()`.
+#[no_mangle]
+pub extern "C" fn ZSTD_rust_params_resolveMaxBlockSize(maxBlockSize: usize) -> usize {
+    if maxBlockSize == 0 {
+        ZSTD_BLOCKSIZE_MAX
+    } else {
+        maxBlockSize
+    }
+}
+
+fn estimate_cdict_size_from_cparams(
+    dict_size: usize,
+    cparams: ZSTD_compressionParameters,
+    dict_load_method: c_int,
+    sizing: ZSTD_rustCDictSizing,
+) -> usize {
+    if check_cparams(cparams) != 0 {
+        return 0;
+    }
+    let match_state_sizing = ZSTD_rustMatchStateSizing {
+        hashLog3Max: sizing.hashLog3Max,
+        matchTSize: sizing.matchTSize,
+        optimalTSize: sizing.optimalTSize,
+        asanRedzoneSize: sizing.asanRedzoneSize,
+    };
+    let row_match_finder = resolve_row_match_finder(ZSTD_RUST_PS_AUTO, cparams);
+    let copied_dict_space = if dict_load_method == 1 {
+        0
+    } else {
+        cwksp_alloc_size(
+            cwksp_align(dict_size, size_of::<usize>()),
+            sizing.asanRedzoneSize,
+        )
+    };
+    cwksp_alloc_size(sizing.cdictSize, sizing.asanRedzoneSize)
+        .wrapping_add(cwksp_alloc_size(
+            sizing.hufWorkspaceSize,
+            sizing.asanRedzoneSize,
+        ))
+        .wrapping_add(estimate_match_state_size(
+            cparams,
+            row_match_finder,
+            true,
+            false,
+            match_state_sizing,
+        ))
+        .wrapping_add(copied_dict_space)
+}
+
+/// Parameter-only leaf for `ZSTD_estimateCDictSize_advanced()`.
+///
+/// C retains ownership of `sizeof(ZSTD_CDict)`, HUF workspace configuration,
+/// and sanitizer workspace policy, then passes them in `sizing`. A NULL sizing
+/// pointer returns zero.
+#[no_mangle]
+pub unsafe extern "C" fn ZSTD_rust_params_estimateCDictSizeFromCParams(
+    dictSize: usize,
+    cparams: ZSTD_compressionParameters,
+    dictLoadMethod: c_int,
+    sizing: *const ZSTD_rustCDictSizing,
+) -> usize {
+    if sizing.is_null() {
+        return 0;
+    }
+    estimate_cdict_size_from_cparams(dictSize, cparams, dictLoadMethod, unsafe { *sizing })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::errors::ERR_isError;
+    use std::mem::{align_of, size_of};
+
+    fn adjust_public(
+        cparams: ZSTD_compressionParameters,
+        src_size: u64,
+        dict_size: usize,
+    ) -> ZSTD_compressionParameters {
+        let src_size = if src_size == 0 {
+            ZSTD_CONTENTSIZE_UNKNOWN
+        } else {
+            src_size
+        };
+        adjust_cparams(
+            clamp_cparams(cparams),
+            src_size,
+            dict_size,
+            ZSTD_RUST_CPM_UNKNOWN,
+            ZSTD_RUST_PS_AUTO,
+        )
+    }
+
+    #[test]
+    fn abi_parameter_layouts_match_zstd_h() {
+        assert_eq!(
+            size_of::<ZSTD_compressionParameters>(),
+            7 * size_of::<u32>()
+        );
+        assert_eq!(align_of::<ZSTD_compressionParameters>(), align_of::<u32>());
+        assert_eq!(size_of::<ZSTD_frameParameters>(), 3 * size_of::<c_int>());
+        assert_eq!(size_of::<ZSTD_parameters>(), 10 * size_of::<u32>());
+        assert_eq!(
+            size_of::<ZSTD_bounds>(),
+            size_of::<usize>() + 2 * size_of::<c_int>()
+        );
+    }
+
+    #[test]
+    fn level_tables_match_representative_clevels_entries() {
+        let large = select_cparams(3, ZSTD_CONTENTSIZE_UNKNOWN, 0, ZSTD_RUST_CPM_UNKNOWN);
+        assert_eq!(
+            large,
+            ZSTD_compressionParameters {
+                windowLog: 21,
+                chainLog: 16,
+                hashLog: 17,
+                searchLog: 1,
+                minMatch: 5,
+                targetLength: 0,
+                strategy: ZSTD_DFAST,
+            }
+        );
+
+        let small = select_cparams(3, 16 * 1024, 0, ZSTD_RUST_CPM_UNKNOWN);
+        assert_eq!(
+            small,
+            ZSTD_compressionParameters {
+                windowLog: 14,
+                chainLog: 14,
+                hashLog: 15,
+                searchLog: 2,
+                minMatch: 4,
+                targetLength: 0,
+                strategy: ZSTD_DFAST,
+            }
+        );
+
+        let fast = select_cparams(-5, ZSTD_CONTENTSIZE_UNKNOWN, 0, ZSTD_RUST_CPM_UNKNOWN);
+        assert_eq!(fast.strategy, ZSTD_FAST);
+        assert_eq!(fast.targetLength, 5);
+        assert_eq!(
+            select_cparams(999, ZSTD_CONTENTSIZE_UNKNOWN, 0, ZSTD_RUST_CPM_UNKNOWN),
+            select_cparams(22, ZSTD_CONTENTSIZE_UNKNOWN, 0, ZSTD_RUST_CPM_UNKNOWN)
+        );
+    }
+
+    #[test]
+    fn adjustment_clamps_and_downsizes_like_the_c_leaf() {
+        let input = ZSTD_compressionParameters {
+            windowLog: 31,
+            chainLog: 30,
+            hashLog: 30,
+            searchLog: 1,
+            minMatch: 3,
+            targetLength: 0,
+            strategy: ZSTD_BTOPT,
+        };
+        let adjusted = adjust_public(input, 1, 0);
+        assert_eq!(adjusted.windowLog, 10);
+        /* C applies WINDOWLOG_ABSOLUTEMIN only after it has used the smaller
+         * temporary window to downsize the hash and chain logs. */
+        assert_eq!(adjusted.hashLog, 7);
+        assert_eq!(adjusted.chainLog, 7);
+        assert_eq!(ZSTD_rust_params_checkCParams(adjusted), 0);
+
+        let clamped = ZSTD_rust_params_clampCParams(ZSTD_compressionParameters {
+            windowLog: u32::MAX,
+            chainLog: 0,
+            hashLog: 0,
+            searchLog: 0,
+            minMatch: 0,
+            targetLength: u32::MAX,
+            strategy: 99,
+        });
+        assert_eq!(clamped.windowLog, ZSTD_WINDOWLOG_MIN as u32);
+        assert_eq!(clamped.chainLog, ZSTD_CHAINLOG_MIN as u32);
+        assert_eq!(clamped.hashLog, ZSTD_HASHLOG_MIN as u32);
+        assert_eq!(clamped.searchLog, ZSTD_SEARCHLOG_MIN as u32);
+        assert_eq!(clamped.minMatch, ZSTD_MINMATCH_MIN as u32);
+        assert_eq!(clamped.targetLength, ZSTD_TARGETLENGTH_MIN as u32);
+        assert_eq!(clamped.strategy, ZSTD_BTULTRA2);
+    }
+
+    #[test]
+    fn checking_and_bounds_preserve_the_public_error_contract() {
+        let valid = select_cparams(1, ZSTD_CONTENTSIZE_UNKNOWN, 0, ZSTD_RUST_CPM_UNKNOWN);
+        assert_eq!(check_cparams(valid), 0);
+        let mut invalid = valid;
+        invalid.minMatch = 2;
+        assert!(ERR_isError(check_cparams(invalid)));
+        let bounds = ZSTD_rust_params_getBounds(ZSTD_C_HASH_LOG);
+        assert_eq!(bounds.error, 0);
+        assert_eq!(bounds.lowerBound, 6);
+        assert_eq!(bounds.upperBound, 30);
+        assert!(ERR_isError(ZSTD_rust_params_getBounds(-1).error));
+    }
+
+    #[test]
+    fn params_default_frame_flags_match_c() {
+        let cparams = select_cparams(5, ZSTD_CONTENTSIZE_UNKNOWN, 0, ZSTD_RUST_CPM_UNKNOWN);
+        let params = ZSTD_rust_params_makeParams(cparams);
+        assert_eq!(params.cParams, cparams);
+        assert_eq!(params.fParams.contentSizeFlag, 1);
+        assert_eq!(params.fParams.checksumFlag, 0);
+        assert_eq!(params.fParams.noDictIDFlag, 0);
+    }
+
+    #[test]
+    fn row_size_preserves_unknown_dictionary_overflow_semantics() {
+        assert_eq!(
+            get_cparam_row_size(ZSTD_CONTENTSIZE_UNKNOWN, 0, ZSTD_RUST_CPM_UNKNOWN),
+            ZSTD_CONTENTSIZE_UNKNOWN
+        );
+        assert_eq!(
+            get_cparam_row_size(ZSTD_CONTENTSIZE_UNKNOWN, 1, ZSTD_RUST_CPM_UNKNOWN),
+            500
+        );
+        assert_eq!(
+            get_cparam_row_size(128 * 1024, 1, ZSTD_RUST_CPM_ATTACH_DICT),
+            128 * 1024
+        );
+    }
+
+    #[test]
+    fn match_state_sizing_reproduces_table_and_row_rules() {
+        let sizing = ZSTD_rustMatchStateSizing {
+            hashLog3Max: 17,
+            matchTSize: 16,
+            optimalTSize: 32,
+            asanRedzoneSize: 0,
+        };
+        let fast = ZSTD_compressionParameters {
+            windowLog: 10,
+            chainLog: 10,
+            hashLog: 10,
+            searchLog: 1,
+            minMatch: 4,
+            targetLength: 0,
+            strategy: ZSTD_FAST,
+        };
+        assert_eq!(
+            estimate_match_state_size(fast, ZSTD_RUST_PS_DISABLE, false, true, sizing),
+            4096 + 128
+        );
+
+        let row = ZSTD_compressionParameters {
+            windowLog: 15,
+            chainLog: 10,
+            hashLog: 10,
+            searchLog: 4,
+            minMatch: 4,
+            targetLength: 0,
+            strategy: ZSTD_GREEDY,
+        };
+        assert_eq!(
+            estimate_match_state_size(row, ZSTD_RUST_PS_ENABLE, false, true, sizing),
+            4096 + 1024 + 128
+        );
+        assert_eq!(ZSTD_rust_params_maxNbSeq(100, 3, 0), 33);
+        assert_eq!(ZSTD_rust_params_maxNbSeq(100, 4, 0), 25);
+        assert_eq!(ZSTD_rust_params_resolveMaxBlockSize(0), 128 * 1024);
+    }
+}