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feat(rust): port FSE entropy decoding

Browse Source 
Move FSE normalized-count parsing, Huffman statistics decoding, FSE table
construction, and FSE stream decompression into Rust. The C source files now
only retain the headers needed by the existing build configuration.

The implementation keeps the public C ABI and verifies C-generated balanced,
skewed, and Huffman-statistics streams. Compression and the higher-level frame
decoder remain C for now.

Test Plan:
- cargo fmt --check
- cargo test --all-targets
- cargo clippy --all-targets -- -D warnings
- cargo build --release
- compile both C shims with -Werror and -Wredundant-decls

Refs: rust/README.md
This commit is contained in:
ddidderr
2026-07-10 20:04:26 +02:00
parent 554a30da41
commit a0f2b2a14c
6 changed files with 1264 additions and 652 deletions
Download Patch File Download Diff File Expand all files Collapse all files
rust/README.md
+8 -4
View File
@@ -17,10 +17,14 @@ zstd ABI:
- `errors`, `debug`, `xxhash`, and `zstd_common` provide common exported ABI
functions and state.
- `common` contains shared frame constants and internal data types.
All entropy coding, compression, decompression, dictionary, legacy, runtime,
and CLI translation units are still C at this initial stage. They must move
before the rewrite is complete. Keeping that boundary explicit prevents a
passing hybrid build from being mistaken for the final all-Rust result.
- Entropy coding
- `entropy_common` reads FSE normalized counts and Huffman statistics.
- `fse_decompress` builds FSE decoding tables and decodes FSE streams.
The remaining compression, general decompression, dictionary, legacy, runtime,
and CLI translation units are still C. They must move before the rewrite is
complete. Keeping that boundary explicit prevents a passing hybrid build from
being mistaken for the final all-Rust result.
## Compatibility boundary
rust/src/entropy_common.rs
+597
View File
@@ -0,0 +1,597 @@
#![allow(non_snake_case)]
use crate::bits::{ZSTD_countTrailingZeros32, ZSTD_highbit32};
use crate::errors::{ERR_getErrorName, ERR_isError, ZstdErrorCode, ERROR};
use crate::mem::{MEM_readLE32, BYTE, U32};
use std::os::raw::{c_char, c_int, c_short, c_uint, c_void};
pub const FSE_VERSION_MAJOR: u32 = 0;
pub const FSE_VERSION_MINOR: u32 = 9;
pub const FSE_VERSION_RELEASE: u32 = 0;
pub const FSE_VERSION_NUMBER: u32 =
FSE_VERSION_MAJOR * 100 * 100 + FSE_VERSION_MINOR * 100 + FSE_VERSION_RELEASE;
pub const FSE_MIN_TABLELOG: u32 = 5;
pub const FSE_TABLELOG_ABSOLUTE_MAX: u32 = 15;
pub const HUF_TABLELOG_MAX: u32 = 12;
pub const HUF_FLAGS_BMI2: c_int = 1 << 0;
// FSE_DECOMPRESS_WKSP_SIZE_U32(6, HUF_TABLELOG_MAX-1) from fse.h / huf.h
const HUF_READ_STATS_WORKSPACE_SIZE_U32: usize = 219;
#[no_mangle]
pub extern "C" fn FSE_versionNumber() -> c_uint {
FSE_VERSION_NUMBER
}
#[no_mangle]
pub extern "C" fn FSE_isError(code: usize) -> c_uint {
ERR_isError(code) as c_uint
}
#[no_mangle]
pub extern "C" fn FSE_getErrorName(code: usize) -> *const c_char {
ERR_getErrorName(code)
}
#[no_mangle]
pub extern "C" fn HUF_isError(code: usize) -> c_uint {
ERR_isError(code) as c_uint
}
#[no_mangle]
pub extern "C" fn HUF_getErrorName(code: usize) -> *const c_char {
ERR_getErrorName(code)
}
fn fse_read_ncount_body(
normalized_counter: *mut c_short,
max_sv_ptr: *mut c_uint,
table_log_ptr: *mut c_uint,
header_buffer: *const c_void,
hb_size: usize,
) -> usize {
unsafe {
if hb_size < 8 {
let mut buffer = [0u8; 8];
if hb_size > 0 {
std::ptr::copy_nonoverlapping(
header_buffer as *const u8,
buffer.as_mut_ptr(),
hb_size,
);
}
let count_size = FSE_readNCount(
normalized_counter,
max_sv_ptr,
table_log_ptr,
buffer.as_ptr() as *const c_void,
buffer.len(),
);
if ERR_isError(count_size) {
return count_size;
}
if count_size > hb_size {
return ERROR(ZstdErrorCode::CorruptionDetected);
}
return count_size;
}
let istart = header_buffer as *const BYTE;
let iend = istart.add(hb_size);
let mut ip = istart;
let max_sv1 = *max_sv_ptr + 1;
// Zero frequency table for all symbols up to maxSVPtr.
std::ptr::write_bytes(normalized_counter, 0, (*max_sv_ptr as usize) + 1);
let mut bit_stream = MEM_readLE32(ip as *const c_void);
let mut nb_bits = ((bit_stream & 0xF) + FSE_MIN_TABLELOG) as i32;
if nb_bits as u32 > FSE_TABLELOG_ABSOLUTE_MAX {
return ERROR(ZstdErrorCode::TableLogTooLarge);
}
bit_stream >>= 4;
let mut bit_count: i32 = 4;
*table_log_ptr = nb_bits as c_uint;
let mut remaining = (1 << nb_bits) + 1;
let mut threshold = 1 << nb_bits;
nb_bits += 1;
let mut charnum: u32 = 0;
let mut previous0 = false;
loop {
if previous0 {
let mut repeats =
(ZSTD_countTrailingZeros32((!bit_stream) | 0x8000_0000) >> 1) as i32;
while repeats >= 12 {
charnum += 3 * 12;
if ip <= iend.sub(7) {
ip = ip.add(3);
} else {
bit_count -= 8 * (iend.offset_from(ip) as i32 - 7);
bit_count &= 31;
ip = iend.sub(4);
}
bit_stream = MEM_readLE32(ip as *const c_void) >> bit_count;
repeats = (ZSTD_countTrailingZeros32((!bit_stream) | 0x8000_0000) >> 1) as i32;
}
charnum += 3 * repeats as u32;
bit_stream >>= 2 * repeats;
bit_count += 2 * repeats;
debug_assert!((bit_stream & 3) < 3);
charnum += bit_stream & 3;
bit_count += 2;
if charnum >= max_sv1 {
break;
}
if ip <= iend.sub(7) || ip.add((bit_count >> 3) as usize) <= iend.sub(4) {
debug_assert!((bit_count >> 3) <= 3);
ip = ip.add((bit_count >> 3) as usize);
bit_count &= 7;
} else {
bit_count -= 8 * (iend.offset_from(ip) as i32 - 4);
bit_count &= 31;
ip = iend.sub(4);
}
bit_stream = MEM_readLE32(ip as *const c_void) >> bit_count;
}
{
let max = (2 * threshold - 1) - remaining;
let mut count: i32;
if (bit_stream & ((threshold as u32) - 1)) < max as u32 {
count = (bit_stream & ((threshold as u32) - 1)) as i32;
bit_count += nb_bits - 1;
} else {
count = (bit_stream & ((2 * threshold as u32) - 1)) as i32;
if count >= threshold {
count -= max;
}
bit_count += nb_bits;
}
count -= 1;
if count >= 0 {
remaining -= count;
} else {
debug_assert!(count == -1);
remaining += count;
}
*normalized_counter.add(charnum as usize) = count as c_short;
charnum += 1;
previous0 = count == 0;
debug_assert!(threshold > 1);
if remaining < threshold {
if remaining <= 1 {
break;
}
nb_bits = ZSTD_highbit32(remaining as u32) as i32 + 1;
threshold = 1 << (nb_bits - 1);
}
if charnum >= max_sv1 {
break;
}
if ip <= iend.sub(7) || ip.add((bit_count >> 3) as usize) <= iend.sub(4) {
ip = ip.add((bit_count >> 3) as usize);
bit_count &= 7;
} else {
bit_count -= 8 * (iend.offset_from(ip) as i32 - 4);
bit_count &= 31;
ip = iend.sub(4);
}
bit_stream = MEM_readLE32(ip as *const c_void) >> bit_count;
}
}
if remaining != 1 {
return ERROR(ZstdErrorCode::CorruptionDetected);
}
if charnum > max_sv1 {
return ERROR(ZstdErrorCode::MaxSymbolValueTooSmall);
}
if bit_count > 32 {
return ERROR(ZstdErrorCode::CorruptionDetected);
}
*max_sv_ptr = charnum - 1;
ip = ip.add(((bit_count + 7) >> 3) as usize);
ip.offset_from(istart) as usize
}
}
#[no_mangle]
pub unsafe extern "C" fn FSE_readNCount_bmi2(
normalized_counter: *mut c_short,
max_sv_ptr: *mut c_uint,
table_log_ptr: *mut c_uint,
header_buffer: *const c_void,
hb_size: usize,
_bmi2: c_int,
) -> usize {
fse_read_ncount_body(
normalized_counter,
max_sv_ptr,
table_log_ptr,
header_buffer,
hb_size,
)
}
#[no_mangle]
pub unsafe extern "C" fn FSE_readNCount(
normalized_counter: *mut c_short,
max_sv_ptr: *mut c_uint,
table_log_ptr: *mut c_uint,
header_buffer: *const c_void,
hb_size: usize,
) -> usize {
FSE_readNCount_bmi2(
normalized_counter,
max_sv_ptr,
table_log_ptr,
header_buffer,
hb_size,
0,
)
}
#[allow(clippy::too_many_arguments)]
fn huf_read_stats_body(
huff_weight: *mut BYTE,
hw_size: usize,
rank_stats: *mut U32,
nb_symbols_ptr: *mut U32,
table_log_ptr: *mut U32,
src: *const c_void,
src_size: usize,
work_space: *mut c_void,
wksp_size: usize,
bmi2: c_int,
) -> usize {
unsafe {
if src_size == 0 {
return ERROR(ZstdErrorCode::SrcSizeWrong);
}
let mut ip = src as *const BYTE;
let mut i_size = *ip as usize;
let o_size: usize;
if i_size >= 128 {
o_size = i_size - 127;
i_size = o_size.div_ceil(2);
if i_size + 1 > src_size {
return ERROR(ZstdErrorCode::SrcSizeWrong);
}
if o_size >= hw_size {
return ERROR(ZstdErrorCode::CorruptionDetected);
}
ip = ip.add(1);
let mut n = 0usize;
while n < o_size {
*huff_weight.add(n) = *ip.add(n / 2) >> 4;
*huff_weight.add(n + 1) = *ip.add(n / 2) & 15;
n += 2;
}
} else {
if i_size + 1 > src_size {
return ERROR(ZstdErrorCode::SrcSizeWrong);
}
let dec = crate::fse_decompress::FSE_decompress_wksp_bmi2(
huff_weight as *mut c_void,
hw_size - 1,
ip.add(1) as *const c_void,
i_size,
6,
work_space,
wksp_size,
bmi2,
);
if ERR_isError(dec) {
return dec;
}
o_size = dec;
}
std::ptr::write_bytes(rank_stats, 0, (HUF_TABLELOG_MAX as usize) + 1);
let mut weight_total: U32 = 0;
for n in 0..o_size {
let w = *huff_weight.add(n) as U32;
if w > HUF_TABLELOG_MAX {
return ERROR(ZstdErrorCode::CorruptionDetected);
}
*rank_stats.add(w as usize) += 1;
weight_total += (1u32 << w) >> 1;
}
if weight_total == 0 {
return ERROR(ZstdErrorCode::CorruptionDetected);
}
let table_log = ZSTD_highbit32(weight_total) + 1;
if table_log > HUF_TABLELOG_MAX {
return ERROR(ZstdErrorCode::CorruptionDetected);
}
*table_log_ptr = table_log;
{
let total = 1u32 << table_log;
let rest = total - weight_total;
let verif = 1u32 << ZSTD_highbit32(rest);
let last_weight = ZSTD_highbit32(rest) + 1;
if verif != rest {
return ERROR(ZstdErrorCode::CorruptionDetected);
}
*huff_weight.add(o_size) = last_weight as BYTE;
*rank_stats.add(last_weight as usize) += 1;
}
let r1 = *rank_stats.add(1);
if r1 < 2 || (r1 & 1) != 0 {
return ERROR(ZstdErrorCode::CorruptionDetected);
}
*nb_symbols_ptr = (o_size + 1) as U32;
i_size + 1
}
}
#[no_mangle]
pub unsafe extern "C" fn HUF_readStats_wksp(
huff_weight: *mut BYTE,
hw_size: usize,
rank_stats: *mut U32,
nb_symbols_ptr: *mut U32,
table_log_ptr: *mut U32,
src: *const c_void,
src_size: usize,
work_space: *mut c_void,
wksp_size: usize,
flags: c_int,
) -> usize {
let bmi2 = if (flags & HUF_FLAGS_BMI2) != 0 { 1 } else { 0 };
huf_read_stats_body(
huff_weight,
hw_size,
rank_stats,
nb_symbols_ptr,
table_log_ptr,
src,
src_size,
work_space,
wksp_size,
bmi2,
)
}
#[no_mangle]
pub unsafe extern "C" fn HUF_readStats(
huff_weight: *mut BYTE,
hw_size: usize,
rank_stats: *mut U32,
nb_symbols_ptr: *mut U32,
table_log_ptr: *mut U32,
src: *const c_void,
src_size: usize,
) -> usize {
let mut wksp = [0u32; HUF_READ_STATS_WORKSPACE_SIZE_U32];
HUF_readStats_wksp(
huff_weight,
hw_size,
rank_stats,
nb_symbols_ptr,
table_log_ptr,
src,
src_size,
wksp.as_mut_ptr() as *mut c_void,
std::mem::size_of_val(&wksp),
0,
)
}
#[cfg(test)]
mod tests {
use super::*;
fn bytes(hex: &str) -> Vec<u8> {
assert_eq!(hex.len() % 2, 0);
hex.as_bytes()
.chunks_exact(2)
.map(|pair| {
let digit = |byte: u8| match byte {
b'0'..=b'9' => byte - b'0',
b'a'..=b'f' => byte - b'a' + 10,
_ => panic!("invalid hex digit"),
};
(digit(pair[0]) << 4) | digit(pair[1])
})
.collect()
}
#[test]
fn fse_version_matches_public_header() {
assert_eq!(FSE_versionNumber(), 900);
}
#[test]
fn fse_read_ncount_matches_reference_header_and_short_prefix_errors() {
// Written by FSE_writeNCount() in the pristine C implementation.
let header = [0xd1u8, 0x28, 0x4a, 0xa9, 0x7c];
let mut normalized = [0x7fffi16; 7];
let mut max_symbol = 6u32;
let mut table_log = 0u32;
let result = unsafe {
FSE_readNCount(
normalized.as_mut_ptr(),
&mut max_symbol,
&mut table_log,
header.as_ptr() as *const c_void,
header.len(),
)
};
assert_eq!(result, header.len());
assert_eq!(max_symbol, 6);
assert_eq!(table_log, 6);
assert_eq!(normalized, [12, 9, 9, 9, 9, 8, 8]);
for prefix_size in 0..header.len() {
normalized.fill(0x7fff);
max_symbol = 6;
table_log = 0;
let result = unsafe {
FSE_readNCount(
normalized.as_mut_ptr(),
&mut max_symbol,
&mut table_log,
header.as_ptr() as *const c_void,
prefix_size,
)
};
assert_eq!(result, ERROR(ZstdErrorCode::CorruptionDetected));
}
}
#[test]
fn huf_read_stats_decodes_direct_even_weight_header() {
let source = [129u8, 0x11];
let mut weights = [0u8; 4];
let mut ranks = [0u32; HUF_TABLELOG_MAX as usize + 1];
let mut symbols = 0u32;
let mut table_log = 0u32;
let result = unsafe {
HUF_readStats(
weights.as_mut_ptr(),
weights.len(),
ranks.as_mut_ptr(),
&mut symbols,
&mut table_log,
source.as_ptr() as *const c_void,
source.len(),
)
};
assert_eq!(result, source.len());
assert_eq!(symbols, 3);
assert_eq!(table_log, 2);
assert_eq!(&weights[..symbols as usize], &[1, 1, 2]);
assert_eq!(ranks[1], 2);
assert_eq!(ranks[2], 1);
}
#[test]
fn huf_read_stats_decodes_direct_odd_weight_header() {
let source = [128u8, 0x1f];
let mut weights = [0u8; 2];
let mut ranks = [0u32; HUF_TABLELOG_MAX as usize + 1];
let mut symbols = 0u32;
let mut table_log = 0u32;
let result = unsafe {
HUF_readStats(
weights.as_mut_ptr(),
weights.len(),
ranks.as_mut_ptr(),
&mut symbols,
&mut table_log,
source.as_ptr() as *const c_void,
source.len(),
)
};
assert_eq!(result, source.len());
assert_eq!(symbols, 2);
assert_eq!(table_log, 1);
assert_eq!(weights, [1, 1]);
assert_eq!(ranks[1], 2);
}
#[test]
fn huf_read_stats_rejects_empty_truncated_and_invalid_trees() {
let mut weights = [0u8; 4];
let mut ranks = [0u32; HUF_TABLELOG_MAX as usize + 1];
let mut symbols = 0u32;
let mut table_log = 0u32;
let empty = unsafe {
HUF_readStats(
weights.as_mut_ptr(),
weights.len(),
ranks.as_mut_ptr(),
&mut symbols,
&mut table_log,
std::ptr::null(),
0,
)
};
assert_eq!(empty, ERROR(ZstdErrorCode::SrcSizeWrong));
let truncated_source = [130u8, 0x11];
let truncated = unsafe {
HUF_readStats(
weights.as_mut_ptr(),
weights.len(),
ranks.as_mut_ptr(),
&mut symbols,
&mut table_log,
truncated_source.as_ptr() as *const c_void,
truncated_source.len(),
)
};
assert_eq!(truncated, ERROR(ZstdErrorCode::SrcSizeWrong));
let invalid_tree_source = [128u8, 0x20];
let invalid_tree = unsafe {
HUF_readStats(
weights.as_mut_ptr(),
weights.len(),
ranks.as_mut_ptr(),
&mut symbols,
&mut table_log,
invalid_tree_source.as_ptr() as *const c_void,
invalid_tree_source.len(),
)
};
assert_eq!(invalid_tree, ERROR(ZstdErrorCode::CorruptionDetected));
}
#[test]
fn huf_read_stats_decodes_fse_compressed_reference_c_header() {
// Produced by HUF_writeCTable_wksp() from the pristine C implementation.
let source = bytes("181010c4a87a61c89e4674d3cb1ee70281b784d34794aa614a");
let expected_weights = bytes(
"0204060306050404040506030604020606020406030605040404050603060402\
0606020406030605040404050603060401060601040603060504030405060306",
);
let expected_ranks = [0u32, 2, 5, 9, 18, 8, 22, 0, 0, 0, 0, 0, 0];
for flags in [0, HUF_FLAGS_BMI2] {
let mut weights = [0u8; 256];
let mut ranks = [0u32; HUF_TABLELOG_MAX as usize + 1];
let mut symbols = 0u32;
let mut table_log = 0u32;
let mut workspace = [0u32; HUF_READ_STATS_WORKSPACE_SIZE_U32];
let result = unsafe {
HUF_readStats_wksp(
weights.as_mut_ptr(),
weights.len(),
ranks.as_mut_ptr(),
&mut symbols,
&mut table_log,
source.as_ptr() as *const c_void,
source.len(),
workspace.as_mut_ptr() as *mut c_void,
std::mem::size_of_val(&workspace),
flags,
)
};
assert_eq!(result, source.len());
assert_eq!(symbols, expected_weights.len() as u32);
assert_eq!(table_log, 10);
assert_eq!(&weights[..symbols as usize], expected_weights);
assert_eq!(ranks, expected_ranks);
}
}
}
rust/src/fse_decompress.rs
+653
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@@ -0,0 +1,653 @@
#![allow(non_snake_case)]
use crate::bits::ZSTD_highbit32;
use crate::bitstream::*;
use crate::errors::{ERR_isError, ZstdErrorCode, ERROR};
use crate::mem::MEM_write64;
use std::os::raw::{c_int, c_uint, c_void};
pub const FSE_MAX_SYMBOL_VALUE: u32 = 255;
pub const FSE_MAX_TABLELOG: u32 = 12;
#[repr(C)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct FSE_DTableHeader {
pub tableLog: u16,
pub fastMode: u16,
}
#[repr(C)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct FSE_decode_t {
pub newState: u16,
pub symbol: u8,
pub nbBits: u8,
}
/// `FSE_DTable` is an opaque `unsigned` in the C API. Its first word stores
/// `FSE_DTableHeader`, followed by `1 << tableLog` `FSE_decode_t` entries.
#[repr(C, align(4))]
pub struct FSE_DTable {
pub header: FSE_DTableHeader,
}
#[repr(C)]
pub struct FSE_DState_t {
pub state: usize,
pub table: *const c_void,
}
#[repr(C)]
pub struct FSE_DecompressWksp {
pub ncount: [i16; (FSE_MAX_SYMBOL_VALUE + 1) as usize],
}
#[inline]
fn FSE_TABLESTEP(table_size: usize) -> usize {
(table_size >> 1) + (table_size >> 3) + 3
}
#[inline]
fn fse_build_dtable_wksp_size(table_log: u32, max_symbol_value: u32) -> Option<usize> {
let table_size = 1usize.checked_shl(table_log)?;
let symbols_size = 2usize.checked_mul(max_symbol_value as usize + 1)?;
symbols_size.checked_add(table_size)?.checked_add(8)
}
#[inline]
fn fse_dtable_size(table_log: u32) -> Option<usize> {
let table_size = 1usize.checked_shl(table_log)?;
(table_size + 1).checked_mul(std::mem::size_of::<FSE_DTable>())
}
#[inline]
fn fse_decompress_wksp_size(table_log: u32, max_symbol_value: u32) -> Option<usize> {
let dtable_u32 = (1usize.checked_shl(table_log)?).checked_add(1)?;
let build_size = fse_build_dtable_wksp_size(table_log, max_symbol_value)?;
let build_u32 = build_size.checked_add(3)? / 4;
// Keep the extra trailing word from FSE_DECOMPRESS_WKSP_SIZE_U32.
let ncount_u32 = ((FSE_MAX_SYMBOL_VALUE as usize + 1) >> 1) + 1;
dtable_u32
.checked_add(1)?
.checked_add(build_u32)?
.checked_add(ncount_u32)?
.checked_mul(4)
}
unsafe fn FSE_buildDTable_internal(
dt: *mut FSE_DTable,
normalized_counter: *const i16,
max_symbol_value: u32,
table_log: u32,
work_space: *mut c_void,
wksp_size: usize,
) -> usize {
let required_wksp = match fse_build_dtable_wksp_size(table_log, max_symbol_value) {
Some(size) => size,
None => return ERROR(ZstdErrorCode::MaxSymbolValueTooLarge),
};
if required_wksp > wksp_size {
return ERROR(ZstdErrorCode::MaxSymbolValueTooLarge);
}
if max_symbol_value > FSE_MAX_SYMBOL_VALUE {
return ERROR(ZstdErrorCode::MaxSymbolValueTooLarge);
}
if table_log > FSE_MAX_TABLELOG {
return ERROR(ZstdErrorCode::TableLogTooLarge);
}
if table_log == 0 {
return ERROR(ZstdErrorCode::Generic);
}
let table_decode = (dt as *mut u8).add(std::mem::size_of::<FSE_DTable>()) as *mut FSE_decode_t;
let symbol_next = work_space as *mut u16;
let spread = symbol_next.add(max_symbol_value as usize + 1) as *mut u8;
let max_sv1 = max_symbol_value + 1;
let table_size = 1usize << table_log;
let mut high_threshold = table_size - 1;
let mut low_probability_count = 0usize;
let mut fast_mode = 1u16;
let large_limit = (1u32 << (table_log - 1)) as i16;
for symbol in 0..max_sv1 {
let count = *normalized_counter.add(symbol as usize);
if count == -1 {
if low_probability_count == table_size {
return ERROR(ZstdErrorCode::Generic);
}
let target = table_size - 1 - low_probability_count;
(*table_decode.add(target)).symbol = symbol as u8;
*symbol_next.add(symbol as usize) = 1;
low_probability_count += 1;
high_threshold = if low_probability_count == table_size {
usize::MAX
} else {
table_size - 1 - low_probability_count
};
} else {
if count >= large_limit {
fast_mode = 0;
}
*symbol_next.add(symbol as usize) = count as u16;
}
}
std::ptr::write(
dt,
FSE_DTable {
header: FSE_DTableHeader {
tableLog: table_log as u16,
fastMode: fast_mode,
},
},
);
if high_threshold == table_size - 1 {
let table_mask = table_size - 1;
let step = FSE_TABLESTEP(table_size);
let mut pos = 0usize;
let mut repeated_symbol = 0u64;
for symbol in 0..max_sv1 {
let count = *normalized_counter.add(symbol as usize);
if count < 0 {
return ERROR(ZstdErrorCode::Generic);
}
let count = count as usize;
MEM_write64(spread.add(pos) as *mut c_void, repeated_symbol);
for offset in (8..count).step_by(8) {
MEM_write64(spread.add(pos + offset) as *mut c_void, repeated_symbol);
}
pos += count;
repeated_symbol = repeated_symbol.wrapping_add(0x0101_0101_0101_0101);
}
let mut position = 0usize;
for symbol_index in (0..table_size).step_by(2) {
for unroll in 0..2 {
let target = (position + unroll * step) & table_mask;
(*table_decode.add(target)).symbol = *spread.add(symbol_index + unroll);
}
position = (position + 2 * step) & table_mask;
}
debug_assert_eq!(position, 0);
} else {
let table_mask = table_size - 1;
let step = FSE_TABLESTEP(table_size);
let mut position = 0usize;
for symbol in 0..max_sv1 {
let count = *normalized_counter.add(symbol as usize);
for _ in 0..count.max(0) as usize {
(*table_decode.add(position)).symbol = symbol as u8;
position = (position + step) & table_mask;
while position > high_threshold {
position = (position + step) & table_mask;
}
}
}
if position != 0 {
return ERROR(ZstdErrorCode::Generic);
}
}
for index in 0..table_size {
let symbol = (*table_decode.add(index)).symbol;
let next_state_ptr = symbol_next.add(symbol as usize);
let next_state = *next_state_ptr as u32;
*next_state_ptr = (*next_state_ptr).wrapping_add(1);
if next_state == 0 {
return ERROR(ZstdErrorCode::Generic);
}
let nb_bits = table_log - ZSTD_highbit32(next_state);
(*table_decode.add(index)).nbBits = nb_bits as u8;
(*table_decode.add(index)).newState =
((next_state << nb_bits).wrapping_sub(table_size as u32)) as u16;
}
0
}
#[no_mangle]
pub unsafe extern "C" fn FSE_buildDTable_wksp(
dt: *mut FSE_DTable,
normalized_counter: *const i16,
max_symbol_value: c_uint,
table_log: c_uint,
work_space: *mut c_void,
wksp_size: usize,
) -> usize {
FSE_buildDTable_internal(
dt,
normalized_counter,
max_symbol_value,
table_log,
work_space,
wksp_size,
)
}
unsafe fn FSE_initDState(
state: *mut FSE_DState_t,
bit_stream: *mut BIT_DStream_t,
dt: *const FSE_DTable,
) {
(*state).state = BIT_readBits(bit_stream, (*dt).header.tableLog as u32);
BIT_reloadDStream(bit_stream);
(*state).table = dt.add(1) as *const c_void;
}
unsafe fn FSE_decodeSymbol(state: *mut FSE_DState_t, bit_stream: *mut BIT_DStream_t) -> u8 {
let entry = &*((*state).table as *const FSE_decode_t).add((*state).state);
let low_bits = BIT_readBits(bit_stream, entry.nbBits as u32);
(*state).state = entry.newState as usize + low_bits;
entry.symbol
}
unsafe fn FSE_decodeSymbolFast(state: *mut FSE_DState_t, bit_stream: *mut BIT_DStream_t) -> u8 {
let entry = &*((*state).table as *const FSE_decode_t).add((*state).state);
let low_bits = BIT_readBitsFast(bit_stream, entry.nbBits as u32);
(*state).state = entry.newState as usize + low_bits;
entry.symbol
}
#[inline]
unsafe fn fse_decode_symbol(
state: *mut FSE_DState_t,
bit_stream: *mut BIT_DStream_t,
fast: bool,
) -> u8 {
if fast {
FSE_decodeSymbolFast(state, bit_stream)
} else {
FSE_decodeSymbol(state, bit_stream)
}
}
unsafe fn FSE_decompress_usingDTable_generic(
dst: *mut c_void,
max_dst_size: usize,
c_src: *const c_void,
c_src_size: usize,
dt: *const FSE_DTable,
fast: bool,
) -> usize {
let mut bit_stream = std::mem::zeroed::<BIT_DStream_t>();
let init_result = BIT_initDStream(&mut bit_stream, c_src, c_src_size);
if ERR_isError(init_result) {
return init_result;
}
let mut state1 = FSE_DState_t {
state: 0,
table: std::ptr::null(),
};
let mut state2 = FSE_DState_t {
state: 0,
table: std::ptr::null(),
};
FSE_initDState(&mut state1, &mut bit_stream, dt);
FSE_initDState(&mut state2, &mut bit_stream, dt);
if BIT_reloadDStream(&mut bit_stream) == BIT_DStream_status::Overflow {
return ERROR(ZstdErrorCode::CorruptionDetected);
}
let output = dst as *mut u8;
let mut output_pos = 0usize;
while BIT_reloadDStream(&mut bit_stream) == BIT_DStream_status::Unfinished
&& output_pos < max_dst_size.saturating_sub(3)
{
*output.add(output_pos) = fse_decode_symbol(&mut state1, &mut bit_stream, fast);
output_pos += 1;
if FSE_MAX_TABLELOG * 2 + 7 > usize::BITS {
BIT_reloadDStream(&mut bit_stream);
}
*output.add(output_pos) = fse_decode_symbol(&mut state2, &mut bit_stream, fast);
output_pos += 1;
if FSE_MAX_TABLELOG * 4 + 7 > usize::BITS
&& BIT_reloadDStream(&mut bit_stream) != BIT_DStream_status::Unfinished
{
break;
}
*output.add(output_pos) = fse_decode_symbol(&mut state1, &mut bit_stream, fast);
output_pos += 1;
if FSE_MAX_TABLELOG * 2 + 7 > usize::BITS {
BIT_reloadDStream(&mut bit_stream);
}
*output.add(output_pos) = fse_decode_symbol(&mut state2, &mut bit_stream, fast);
output_pos += 1;
}
loop {
if max_dst_size.saturating_sub(output_pos) < 2 {
return ERROR(ZstdErrorCode::DstSizeTooSmall);
}
*output.add(output_pos) = fse_decode_symbol(&mut state1, &mut bit_stream, fast);
output_pos += 1;
if BIT_reloadDStream(&mut bit_stream) == BIT_DStream_status::Overflow {
*output.add(output_pos) = fse_decode_symbol(&mut state2, &mut bit_stream, fast);
output_pos += 1;
break;
}
if max_dst_size.saturating_sub(output_pos) < 2 {
return ERROR(ZstdErrorCode::DstSizeTooSmall);
}
*output.add(output_pos) = fse_decode_symbol(&mut state2, &mut bit_stream, fast);
output_pos += 1;
if BIT_reloadDStream(&mut bit_stream) == BIT_DStream_status::Overflow {
*output.add(output_pos) = fse_decode_symbol(&mut state1, &mut bit_stream, fast);
output_pos += 1;
break;
}
}
output_pos
}
#[allow(clippy::too_many_arguments)]
unsafe fn FSE_decompress_wksp_body(
dst: *mut c_void,
dst_capacity: usize,
c_src: *const c_void,
mut c_src_size: usize,
max_log: u32,
work_space: *mut c_void,
wksp_size: usize,
bmi2: c_int,
) -> usize {
if wksp_size < std::mem::size_of::<FSE_DecompressWksp>() {
return ERROR(ZstdErrorCode::Generic);
}
let input_start = c_src as *const u8;
let wksp = work_space as *mut FSE_DecompressWksp;
let dtable =
(work_space as *mut u8).add(std::mem::size_of::<FSE_DecompressWksp>()) as *mut FSE_DTable;
let mut table_log = 0u32;
let mut max_symbol_value = FSE_MAX_SYMBOL_VALUE;
let ncount_length = crate::entropy_common::FSE_readNCount_bmi2(
(*wksp).ncount.as_mut_ptr(),
&mut max_symbol_value,
&mut table_log,
c_src,
c_src_size,
bmi2,
);
if ERR_isError(ncount_length) {
return ncount_length;
}
if table_log > max_log {
return ERROR(ZstdErrorCode::TableLogTooLarge);
}
if ncount_length > c_src_size {
return ERROR(ZstdErrorCode::CorruptionDetected);
}
let required_size = match fse_decompress_wksp_size(table_log, max_symbol_value) {
Some(size) => size,
None => return ERROR(ZstdErrorCode::TableLogTooLarge),
};
if required_size > wksp_size {
return ERROR(ZstdErrorCode::TableLogTooLarge);
}
let dtable_size = fse_dtable_size(table_log).expect("validated FSE table dimensions fit usize");
let build_offset = std::mem::size_of::<FSE_DecompressWksp>() + dtable_size;
let build_workspace = (work_space as *mut u8).add(build_offset) as *mut c_void;
let build_workspace_size = wksp_size - build_offset;
let build_result = FSE_buildDTable_internal(
dtable,
(*wksp).ncount.as_ptr(),
max_symbol_value,
table_log,
build_workspace,
build_workspace_size,
);
if ERR_isError(build_result) {
return build_result;
}
let payload = input_start.add(ncount_length);
c_src_size -= ncount_length;
FSE_decompress_usingDTable_generic(
dst,
dst_capacity,
payload as *const c_void,
c_src_size,
dtable,
(*dtable).header.fastMode != 0,
)
}
#[no_mangle]
pub unsafe extern "C" fn FSE_decompress_wksp_bmi2(
dst: *mut c_void,
dst_capacity: usize,
c_src: *const c_void,
c_src_size: usize,
max_log: c_uint,
work_space: *mut c_void,
wksp_size: usize,
bmi2: c_int,
) -> usize {
FSE_decompress_wksp_body(
dst,
dst_capacity,
c_src,
c_src_size,
max_log,
work_space,
wksp_size,
bmi2,
)
}
#[cfg(test)]
mod tests {
use super::*;
fn dtable_storage(table_log: u32) -> Vec<u32> {
vec![0; 1 + (1usize << table_log)]
}
fn bytes(hex: &str) -> Vec<u8> {
assert_eq!(hex.len() % 2, 0);
hex.as_bytes()
.chunks_exact(2)
.map(|pair| {
let digit = |byte: u8| match byte {
b'0'..=b'9' => byte - b'0',
b'a'..=b'f' => byte - b'a' + 10,
_ => panic!("invalid hex digit"),
};
(digit(pair[0]) << 4) | digit(pair[1])
})
.collect()
}
fn decompress(compressed: &[u8], capacity: usize) -> (usize, Vec<u8>) {
let mut output = vec![0u8; capacity];
let mut workspace = vec![0u32; 6000];
let result = unsafe {
FSE_decompress_wksp_bmi2(
output.as_mut_ptr() as *mut c_void,
output.len(),
compressed.as_ptr() as *const c_void,
compressed.len(),
FSE_MAX_TABLELOG,
workspace.as_mut_ptr() as *mut c_void,
workspace.len() * 4,
0,
)
};
(result, output)
}
#[test]
fn abi_layout_matches_fse_h() {
assert_eq!(std::mem::size_of::<FSE_DTable>(), 4);
assert_eq!(std::mem::align_of::<FSE_DTable>(), 4);
assert_eq!(std::mem::size_of::<FSE_decode_t>(), 4);
assert_eq!(std::mem::size_of::<FSE_DecompressWksp>(), 512);
}
#[test]
fn build_dtable_advances_each_symbol_state() {
let normalized = [8i16, 8, 8, 8];
let mut table = dtable_storage(5);
let mut workspace = vec![0u32; 64];
let result = unsafe {
FSE_buildDTable_wksp(
table.as_mut_ptr() as *mut FSE_DTable,
normalized.as_ptr(),
3,
5,
workspace.as_mut_ptr() as *mut c_void,
workspace.len() * 4,
)
};
assert_eq!(result, 0);
let header = unsafe { &*(table.as_ptr() as *const FSE_DTableHeader) };
assert_eq!(
*header,
FSE_DTableHeader {
tableLog: 5,
fastMode: 1
}
);
let entries = unsafe {
std::slice::from_raw_parts(
table.as_ptr().add(1) as *const FSE_decode_t,
1 << header.tableLog,
)
};
for symbol in 0..4u8 {
let mut states: Vec<u16> = entries
.iter()
.filter(|entry| entry.symbol == symbol)
.map(|entry| {
assert_eq!(entry.nbBits, 2);
entry.newState
})
.collect();
states.sort_unstable();
assert_eq!(states, [0, 4, 8, 12, 16, 20, 24, 28]);
}
}
#[test]
fn build_dtable_places_low_probability_symbols_at_end() {
let normalized = [-1i16, -1, 15, 15];
let mut table = dtable_storage(5);
let mut workspace = vec![0u32; 64];
let result = unsafe {
FSE_buildDTable_wksp(
table.as_mut_ptr() as *mut FSE_DTable,
normalized.as_ptr(),
3,
5,
workspace.as_mut_ptr() as *mut c_void,
workspace.len() * 4,
)
};
assert_eq!(result, 0);
let entries =
unsafe { std::slice::from_raw_parts(table.as_ptr().add(1) as *const FSE_decode_t, 32) };
assert_eq!(entries[31].symbol, 0);
assert_eq!(entries[30].symbol, 1);
assert_eq!(entries[31].nbBits, 5);
assert_eq!(entries[31].newState, 0);
assert_eq!(entries[30].nbBits, 5);
assert_eq!(entries[30].newState, 0);
}
#[test]
fn build_dtable_reports_workspace_and_dimension_errors() {
let normalized = [32i16];
let mut table = dtable_storage(5);
let mut workspace = [0u32; 1];
let too_small = unsafe {
FSE_buildDTable_wksp(
table.as_mut_ptr() as *mut FSE_DTable,
normalized.as_ptr(),
0,
5,
workspace.as_mut_ptr() as *mut c_void,
workspace.len() * 4,
)
};
assert_eq!(too_small, ERROR(ZstdErrorCode::MaxSymbolValueTooLarge));
let mut large_workspace = vec![0u32; 4096];
let table_log_too_large = unsafe {
FSE_buildDTable_wksp(
table.as_mut_ptr() as *mut FSE_DTable,
normalized.as_ptr(),
0,
FSE_MAX_TABLELOG + 1,
large_workspace.as_mut_ptr() as *mut c_void,
large_workspace.len() * 4,
)
};
assert_eq!(table_log_too_large, ERROR(ZstdErrorCode::TableLogTooLarge));
}
#[test]
fn decompression_workspace_size_matches_c_macro() {
assert_eq!(fse_build_dtable_wksp_size(6, 11), Some(96));
assert_eq!(fse_decompress_wksp_size(6, 11), Some(876));
assert_eq!(fse_dtable_size(6), Some(260));
}
#[test]
fn decompresses_balanced_reference_c_stream() {
// Generated by the pristine HEAD implementation using a 257-byte,
// seven-symbol input and FSE_compress_usingCTable().
let compressed = bytes(
"d1284aa97cd5fce4cd4fdefce4cd4fdefce4cd4fdefce4cd4fdefce4cd4fdefc\
e4cd4fdefce4cd4fdefce4cd4fdefce4cd4fdefce4cd4fdefce4cd4fdefce4cd\
4fdefce4cd4fdefce4cd4fdefce4cd4fdefce4cd4fdefce4cd4fdefce4cd4fde\
c415",
);
let expected: Vec<u8> = (0..257).map(|index| (index % 7) as u8).collect();
let (result, output) = decompress(&compressed, expected.len());
assert_eq!(result, expected.len());
assert_eq!(output, expected);
}
#[test]
fn decompresses_skewed_reference_c_stream_and_reports_small_output() {
// Exercises low-probability symbols and the non-fast decode path.
let compressed = bytes(
"0100800c000000003dc2200147143cc008a2061471b400828c42a4a2871844e090\
820e18429481428e2a40a0518858d41103093852e001460835a0c8a1051034142\
20bf00f",
);
let expected: Vec<u8> = (0..511)
.map(|index| {
if index % 10 != 0 {
3
} else {
(index % 17) as u8
}
})
.collect();
let (result, output) = decompress(&compressed, expected.len());
assert_eq!(result, expected.len());
assert_eq!(output, expected);
let (too_small, _) = decompress(&compressed, expected.len() - 1);
assert_eq!(too_small, ERROR(ZstdErrorCode::DstSizeTooSmall));
}
}
rust/src/lib.rs
+2
View File
@@ -5,7 +5,9 @@ pub mod bitstream;
pub mod common;
pub mod cpu;
pub mod debug;
pub mod entropy_common;
pub mod errors;
pub mod fse_decompress;
pub mod mem;
pub mod xxhash;
pub mod zstd_common;