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Duckstation/dep/zstd/lib/decompress/zstd_decompress_block.c

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dep: Add zstd
2022-08-18 09:30:13 +00:00
/*
* Copyright (c) Yann Collet, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under both the BSD-style license (found in the
* LICENSE file in the root directory of this source tree) and the GPLv2 (found
* in the COPYING file in the root directory of this source tree).
* You may select, at your option, one of the above-listed licenses.
*/
/* zstd_decompress_block :
* this module takes care of decompressing _compressed_ block */
/*-*******************************************************
* Dependencies
*********************************************************/
#include "../common/zstd_deps.h" /* ZSTD_memcpy, ZSTD_memmove, ZSTD_memset */
#include "../common/compiler.h" /* prefetch */
#include "../common/cpu.h" /* bmi2 */
#include "../common/mem.h" /* low level memory routines */
#define FSE_STATIC_LINKING_ONLY
#include "../common/fse.h"
#define HUF_STATIC_LINKING_ONLY
#include "../common/huf.h"
#include "../common/zstd_internal.h"
#include "zstd_decompress_internal.h" /* ZSTD_DCtx */
#include "zstd_ddict.h" /* ZSTD_DDictDictContent */
#include "zstd_decompress_block.h"
/*_*******************************************************
* Macros
**********************************************************/
/* These two optional macros force the use one way or another of the two
* ZSTD_decompressSequences implementations. You can't force in both directions
* at the same time.
*/
#if defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \
defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG)
#error "Cannot force the use of the short and the long ZSTD_decompressSequences variants!"
#endif
/*_*******************************************************
* Memory operations
**********************************************************/
static void ZSTD_copy4(void* dst, const void* src) { ZSTD_memcpy(dst, src, 4); }
/*-*************************************************************
* Block decoding
***************************************************************/
/*! ZSTD_getcBlockSize() :
* Provides the size of compressed block from block header `src` */
size_t ZSTD_getcBlockSize(const void* src, size_t srcSize,
blockProperties_t* bpPtr)
{
RETURN_ERROR_IF(srcSize < ZSTD_blockHeaderSize, srcSize_wrong, "");
{ U32 const cBlockHeader = MEM_readLE24(src);
U32 const cSize = cBlockHeader >> 3;
bpPtr->lastBlock = cBlockHeader & 1;
bpPtr->blockType = (blockType_e)((cBlockHeader >> 1) & 3);
bpPtr->origSize = cSize; /* only useful for RLE */
if (bpPtr->blockType == bt_rle) return 1;
RETURN_ERROR_IF(bpPtr->blockType == bt_reserved, corruption_detected, "");
return cSize;
}
}
/* Allocate buffer for literals, either overlapping current dst, or split between dst and litExtraBuffer, or stored entirely within litExtraBuffer */
static void ZSTD_allocateLiteralsBuffer(ZSTD_DCtx* dctx, void* const dst, const size_t dstCapacity, const size_t litSize,
const streaming_operation streaming, const size_t expectedWriteSize, const unsigned splitImmediately)
{
if (streaming == not_streaming && dstCapacity > ZSTD_BLOCKSIZE_MAX + WILDCOPY_OVERLENGTH + litSize + WILDCOPY_OVERLENGTH)
{
/* room for litbuffer to fit without read faulting */
dctx->litBuffer = (BYTE*)dst + ZSTD_BLOCKSIZE_MAX + WILDCOPY_OVERLENGTH;
dctx->litBufferEnd = dctx->litBuffer + litSize;
dctx->litBufferLocation = ZSTD_in_dst;
}
else if (litSize > ZSTD_LITBUFFEREXTRASIZE)
{
/* won't fit in litExtraBuffer, so it will be split between end of dst and extra buffer */
if (splitImmediately) {
/* won't fit in litExtraBuffer, so it will be split between end of dst and extra buffer */
dctx->litBuffer = (BYTE*)dst + expectedWriteSize - litSize + ZSTD_LITBUFFEREXTRASIZE - WILDCOPY_OVERLENGTH;
dctx->litBufferEnd = dctx->litBuffer + litSize - ZSTD_LITBUFFEREXTRASIZE;
}
else {
/* initially this will be stored entirely in dst during huffman decoding, it will partially shifted to litExtraBuffer after */
dctx->litBuffer = (BYTE*)dst + expectedWriteSize - litSize;
dctx->litBufferEnd = (BYTE*)dst + expectedWriteSize;
}
dctx->litBufferLocation = ZSTD_split;
}
else
{
/* fits entirely within litExtraBuffer, so no split is necessary */
dctx->litBuffer = dctx->litExtraBuffer;
dctx->litBufferEnd = dctx->litBuffer + litSize;
dctx->litBufferLocation = ZSTD_not_in_dst;
}
}
/* Hidden declaration for fullbench */
size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
const void* src, size_t srcSize,
void* dst, size_t dstCapacity, const streaming_operation streaming);
/*! ZSTD_decodeLiteralsBlock() :
* Where it is possible to do so without being stomped by the output during decompression, the literals block will be stored
* in the dstBuffer. If there is room to do so, it will be stored in full in the excess dst space after where the current
* block will be output. Otherwise it will be stored at the end of the current dst blockspace, with a small portion being
* stored in dctx->litExtraBuffer to help keep it "ahead" of the current output write.
*
* @return : nb of bytes read from src (< srcSize )
* note : symbol not declared but exposed for fullbench */
size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
const void* src, size_t srcSize, /* note : srcSize < BLOCKSIZE */
void* dst, size_t dstCapacity, const streaming_operation streaming)
{
DEBUGLOG(5, "ZSTD_decodeLiteralsBlock");
RETURN_ERROR_IF(srcSize < MIN_CBLOCK_SIZE, corruption_detected, "");
{ const BYTE* const istart = (const BYTE*) src;
symbolEncodingType_e const litEncType = (symbolEncodingType_e)(istart[0] & 3);
switch(litEncType)
{
case set_repeat:
DEBUGLOG(5, "set_repeat flag : re-using stats from previous compressed literals block");
RETURN_ERROR_IF(dctx->litEntropy==0, dictionary_corrupted, "");
ZSTD_FALLTHROUGH;
case set_compressed:
RETURN_ERROR_IF(srcSize < 5, corruption_detected, "srcSize >= MIN_CBLOCK_SIZE == 3; here we need up to 5 for case 3");
{ size_t lhSize, litSize, litCSize;
U32 singleStream=0;
U32 const lhlCode = (istart[0] >> 2) & 3;
U32 const lhc = MEM_readLE32(istart);
size_t hufSuccess;
size_t expectedWriteSize = MIN(ZSTD_BLOCKSIZE_MAX, dstCapacity);
switch(lhlCode)
{
case 0: case 1: default: /* note : default is impossible, since lhlCode into [0..3] */
/* 2 - 2 - 10 - 10 */
singleStream = !lhlCode;
lhSize = 3;
litSize = (lhc >> 4) & 0x3FF;
litCSize = (lhc >> 14) & 0x3FF;
break;
case 2:
/* 2 - 2 - 14 - 14 */
lhSize = 4;
litSize = (lhc >> 4) & 0x3FFF;
litCSize = lhc >> 18;
break;
case 3:
/* 2 - 2 - 18 - 18 */
lhSize = 5;
litSize = (lhc >> 4) & 0x3FFFF;
litCSize = (lhc >> 22) + ((size_t)istart[4] << 10);
break;
}
RETURN_ERROR_IF(litSize > 0 && dst == NULL, dstSize_tooSmall, "NULL not handled");
RETURN_ERROR_IF(litSize > ZSTD_BLOCKSIZE_MAX, corruption_detected, "");
RETURN_ERROR_IF(litCSize + lhSize > srcSize, corruption_detected, "");
RETURN_ERROR_IF(expectedWriteSize < litSize , dstSize_tooSmall, "");
ZSTD_allocateLiteralsBuffer(dctx, dst, dstCapacity, litSize, streaming, expectedWriteSize, 0);
/* prefetch huffman table if cold */
if (dctx->ddictIsCold && (litSize > 768 /* heuristic */)) {
PREFETCH_AREA(dctx->HUFptr, sizeof(dctx->entropy.hufTable));
}
if (litEncType==set_repeat) {
if (singleStream) {
hufSuccess = HUF_decompress1X_usingDTable_bmi2(
dctx->litBuffer, litSize, istart+lhSize, litCSize,
dctx->HUFptr, ZSTD_DCtx_get_bmi2(dctx));
} else {
hufSuccess = HUF_decompress4X_usingDTable_bmi2(
dctx->litBuffer, litSize, istart+lhSize, litCSize,
dctx->HUFptr, ZSTD_DCtx_get_bmi2(dctx));
}
} else {
if (singleStream) {
#if defined(HUF_FORCE_DECOMPRESS_X2)
hufSuccess = HUF_decompress1X_DCtx_wksp(
dctx->entropy.hufTable, dctx->litBuffer, litSize,
istart+lhSize, litCSize, dctx->workspace,
sizeof(dctx->workspace));
#else
hufSuccess = HUF_decompress1X1_DCtx_wksp_bmi2(
dctx->entropy.hufTable, dctx->litBuffer, litSize,
istart+lhSize, litCSize, dctx->workspace,
sizeof(dctx->workspace), ZSTD_DCtx_get_bmi2(dctx));
#endif
} else {
hufSuccess = HUF_decompress4X_hufOnly_wksp_bmi2(
dctx->entropy.hufTable, dctx->litBuffer, litSize,
istart+lhSize, litCSize, dctx->workspace,
sizeof(dctx->workspace), ZSTD_DCtx_get_bmi2(dctx));
}
}
if (dctx->litBufferLocation == ZSTD_split)
{
ZSTD_memcpy(dctx->litExtraBuffer, dctx->litBufferEnd - ZSTD_LITBUFFEREXTRASIZE, ZSTD_LITBUFFEREXTRASIZE);
ZSTD_memmove(dctx->litBuffer + ZSTD_LITBUFFEREXTRASIZE - WILDCOPY_OVERLENGTH, dctx->litBuffer, litSize - ZSTD_LITBUFFEREXTRASIZE);
dctx->litBuffer += ZSTD_LITBUFFEREXTRASIZE - WILDCOPY_OVERLENGTH;
dctx->litBufferEnd -= WILDCOPY_OVERLENGTH;
}
RETURN_ERROR_IF(HUF_isError(hufSuccess), corruption_detected, "");
dctx->litPtr = dctx->litBuffer;
dctx->litSize = litSize;
dctx->litEntropy = 1;
if (litEncType==set_compressed) dctx->HUFptr = dctx->entropy.hufTable;
return litCSize + lhSize;
}
case set_basic:
{ size_t litSize, lhSize;
U32 const lhlCode = ((istart[0]) >> 2) & 3;
size_t expectedWriteSize = MIN(ZSTD_BLOCKSIZE_MAX, dstCapacity);
switch(lhlCode)
{
case 0: case 2: default: /* note : default is impossible, since lhlCode into [0..3] */
lhSize = 1;
litSize = istart[0] >> 3;
break;
case 1:
lhSize = 2;
litSize = MEM_readLE16(istart) >> 4;
break;
case 3:
lhSize = 3;
litSize = MEM_readLE24(istart) >> 4;
break;
}
RETURN_ERROR_IF(litSize > 0 && dst == NULL, dstSize_tooSmall, "NULL not handled");
RETURN_ERROR_IF(expectedWriteSize < litSize, dstSize_tooSmall, "");
ZSTD_allocateLiteralsBuffer(dctx, dst, dstCapacity, litSize, streaming, expectedWriteSize, 1);
if (lhSize+litSize+WILDCOPY_OVERLENGTH > srcSize) { /* risk reading beyond src buffer with wildcopy */
RETURN_ERROR_IF(litSize+lhSize > srcSize, corruption_detected, "");
if (dctx->litBufferLocation == ZSTD_split)
{
ZSTD_memcpy(dctx->litBuffer, istart + lhSize, litSize - ZSTD_LITBUFFEREXTRASIZE);
ZSTD_memcpy(dctx->litExtraBuffer, istart + lhSize + litSize - ZSTD_LITBUFFEREXTRASIZE, ZSTD_LITBUFFEREXTRASIZE);
}
else
{
ZSTD_memcpy(dctx->litBuffer, istart + lhSize, litSize);
}
dctx->litPtr = dctx->litBuffer;
dctx->litSize = litSize;
return lhSize+litSize;
}
/* direct reference into compressed stream */
dctx->litPtr = istart+lhSize;
dctx->litSize = litSize;
dctx->litBufferEnd = dctx->litPtr + litSize;
dctx->litBufferLocation = ZSTD_not_in_dst;
return lhSize+litSize;
}
case set_rle:
{ U32 const lhlCode = ((istart[0]) >> 2) & 3;
size_t litSize, lhSize;
size_t expectedWriteSize = MIN(ZSTD_BLOCKSIZE_MAX, dstCapacity);
switch(lhlCode)
{
case 0: case 2: default: /* note : default is impossible, since lhlCode into [0..3] */
lhSize = 1;
litSize = istart[0] >> 3;
break;
case 1:
lhSize = 2;
litSize = MEM_readLE16(istart) >> 4;
break;
case 3:
lhSize = 3;
litSize = MEM_readLE24(istart) >> 4;
RETURN_ERROR_IF(srcSize<4, corruption_detected, "srcSize >= MIN_CBLOCK_SIZE == 3; here we need lhSize+1 = 4");
break;
}
RETURN_ERROR_IF(litSize > 0 && dst == NULL, dstSize_tooSmall, "NULL not handled");
RETURN_ERROR_IF(litSize > ZSTD_BLOCKSIZE_MAX, corruption_detected, "");
RETURN_ERROR_IF(expectedWriteSize < litSize, dstSize_tooSmall, "");
ZSTD_allocateLiteralsBuffer(dctx, dst, dstCapacity, litSize, streaming, expectedWriteSize, 1);
if (dctx->litBufferLocation == ZSTD_split)
{
ZSTD_memset(dctx->litBuffer, istart[lhSize], litSize - ZSTD_LITBUFFEREXTRASIZE);
ZSTD_memset(dctx->litExtraBuffer, istart[lhSize], ZSTD_LITBUFFEREXTRASIZE);
}
else
{
ZSTD_memset(dctx->litBuffer, istart[lhSize], litSize);
}
dctx->litPtr = dctx->litBuffer;
dctx->litSize = litSize;
return lhSize+1;
}
default:
RETURN_ERROR(corruption_detected, "impossible");
}
}
}
/* Default FSE distribution tables.
* These are pre-calculated FSE decoding tables using default distributions as defined in specification :
* https://github.com/facebook/zstd/blob/release/doc/zstd_compression_format.md#default-distributions
* They were generated programmatically with following method :
* - start from default distributions, present in /lib/common/zstd_internal.h
* - generate tables normally, using ZSTD_buildFSETable()
* - printout the content of tables
* - pretify output, report below, test with fuzzer to ensure it's correct */
/* Default FSE distribution table for Literal Lengths */
static const ZSTD_seqSymbol LL_defaultDTable[(1<<LL_DEFAULTNORMLOG)+1] = {
{ 1, 1, 1, LL_DEFAULTNORMLOG}, /* header : fastMode, tableLog */
/* nextState, nbAddBits, nbBits, baseVal */
{ 0, 0, 4, 0}, { 16, 0, 4, 0},
{ 32, 0, 5, 1}, { 0, 0, 5, 3},
{ 0, 0, 5, 4}, { 0, 0, 5, 6},
{ 0, 0, 5, 7}, { 0, 0, 5, 9},
{ 0, 0, 5, 10}, { 0, 0, 5, 12},
{ 0, 0, 6, 14}, { 0, 1, 5, 16},
{ 0, 1, 5, 20}, { 0, 1, 5, 22},
{ 0, 2, 5, 28}, { 0, 3, 5, 32},
{ 0, 4, 5, 48}, { 32, 6, 5, 64},
{ 0, 7, 5, 128}, { 0, 8, 6, 256},
{ 0, 10, 6, 1024}, { 0, 12, 6, 4096},
{ 32, 0, 4, 0}, { 0, 0, 4, 1},
{ 0, 0, 5, 2}, { 32, 0, 5, 4},
{ 0, 0, 5, 5}, { 32, 0, 5, 7},
{ 0, 0, 5, 8}, { 32, 0, 5, 10},
{ 0, 0, 5, 11}, { 0, 0, 6, 13},
{ 32, 1, 5, 16}, { 0, 1, 5, 18},
{ 32, 1, 5, 22}, { 0, 2, 5, 24},
{ 32, 3, 5, 32}, { 0, 3, 5, 40},
{ 0, 6, 4, 64}, { 16, 6, 4, 64},
{ 32, 7, 5, 128}, { 0, 9, 6, 512},
{ 0, 11, 6, 2048}, { 48, 0, 4, 0},
{ 16, 0, 4, 1}, { 32, 0, 5, 2},
{ 32, 0, 5, 3}, { 32, 0, 5, 5},
{ 32, 0, 5, 6}, { 32, 0, 5, 8},
{ 32, 0, 5, 9}, { 32, 0, 5, 11},
{ 32, 0, 5, 12}, { 0, 0, 6, 15},
{ 32, 1, 5, 18}, { 32, 1, 5, 20},
{ 32, 2, 5, 24}, { 32, 2, 5, 28},
{ 32, 3, 5, 40}, { 32, 4, 5, 48},
{ 0, 16, 6,65536}, { 0, 15, 6,32768},
{ 0, 14, 6,16384}, { 0, 13, 6, 8192},
}; /* LL_defaultDTable */
/* Default FSE distribution table for Offset Codes */
static const ZSTD_seqSymbol OF_defaultDTable[(1<<OF_DEFAULTNORMLOG)+1] = {
{ 1, 1, 1, OF_DEFAULTNORMLOG}, /* header : fastMode, tableLog */
/* nextState, nbAddBits, nbBits, baseVal */
{ 0, 0, 5, 0}, { 0, 6, 4, 61},
{ 0, 9, 5, 509}, { 0, 15, 5,32765},
{ 0, 21, 5,2097149}, { 0, 3, 5, 5},
{ 0, 7, 4, 125}, { 0, 12, 5, 4093},
{ 0, 18, 5,262141}, { 0, 23, 5,8388605},
{ 0, 5, 5, 29}, { 0, 8, 4, 253},
{ 0, 14, 5,16381}, { 0, 20, 5,1048573},
{ 0, 2, 5, 1}, { 16, 7, 4, 125},
{ 0, 11, 5, 2045}, { 0, 17, 5,131069},
{ 0, 22, 5,4194301}, { 0, 4, 5, 13},
{ 16, 8, 4, 253}, { 0, 13, 5, 8189},
{ 0, 19, 5,524285}, { 0, 1, 5, 1},
{ 16, 6, 4, 61}, { 0, 10, 5, 1021},
{ 0, 16, 5,65533}, { 0, 28, 5,268435453},
{ 0, 27, 5,134217725}, { 0, 26, 5,67108861},
{ 0, 25, 5,33554429}, { 0, 24, 5,16777213},
}; /* OF_defaultDTable */
/* Default FSE distribution table for Match Lengths */
static const ZSTD_seqSymbol ML_defaultDTable[(1<<ML_DEFAULTNORMLOG)+1] = {
{ 1, 1, 1, ML_DEFAULTNORMLOG}, /* header : fastMode, tableLog */
/* nextState, nbAddBits, nbBits, baseVal */
{ 0, 0, 6, 3}, { 0, 0, 4, 4},
{ 32, 0, 5, 5}, { 0, 0, 5, 6},
{ 0, 0, 5, 8}, { 0, 0, 5, 9},
{ 0, 0, 5, 11}, { 0, 0, 6, 13},
{ 0, 0, 6, 16}, { 0, 0, 6, 19},
{ 0, 0, 6, 22}, { 0, 0, 6, 25},
{ 0, 0, 6, 28}, { 0, 0, 6, 31},
{ 0, 0, 6, 34}, { 0, 1, 6, 37},
{ 0, 1, 6, 41}, { 0, 2, 6, 47},
{ 0, 3, 6, 59}, { 0, 4, 6, 83},
{ 0, 7, 6, 131}, { 0, 9, 6, 515},
{ 16, 0, 4, 4}, { 0, 0, 4, 5},
{ 32, 0, 5, 6}, { 0, 0, 5, 7},
{ 32, 0, 5, 9}, { 0, 0, 5, 10},
{ 0, 0, 6, 12}, { 0, 0, 6, 15},
{ 0, 0, 6, 18}, { 0, 0, 6, 21},
{ 0, 0, 6, 24}, { 0, 0, 6, 27},
{ 0, 0, 6, 30}, { 0, 0, 6, 33},
{ 0, 1, 6, 35}, { 0, 1, 6, 39},
{ 0, 2, 6, 43}, { 0, 3, 6, 51},
{ 0, 4, 6, 67}, { 0, 5, 6, 99},
{ 0, 8, 6, 259}, { 32, 0, 4, 4},
{ 48, 0, 4, 4}, { 16, 0, 4, 5},
{ 32, 0, 5, 7}, { 32, 0, 5, 8},
{ 32, 0, 5, 10}, { 32, 0, 5, 11},
{ 0, 0, 6, 14}, { 0, 0, 6, 17},
{ 0, 0, 6, 20}, { 0, 0, 6, 23},
{ 0, 0, 6, 26}, { 0, 0, 6, 29},
{ 0, 0, 6, 32}, { 0, 16, 6,65539},
{ 0, 15, 6,32771}, { 0, 14, 6,16387},
{ 0, 13, 6, 8195}, { 0, 12, 6, 4099},
{ 0, 11, 6, 2051}, { 0, 10, 6, 1027},
}; /* ML_defaultDTable */
static void ZSTD_buildSeqTable_rle(ZSTD_seqSymbol* dt, U32 baseValue, U8 nbAddBits)
{
void* ptr = dt;
ZSTD_seqSymbol_header* const DTableH = (ZSTD_seqSymbol_header*)ptr;
ZSTD_seqSymbol* const cell = dt + 1;
DTableH->tableLog = 0;
DTableH->fastMode = 0;
cell->nbBits = 0;
cell->nextState = 0;
assert(nbAddBits < 255);
cell->nbAdditionalBits = nbAddBits;
cell->baseValue = baseValue;
}
/* ZSTD_buildFSETable() :
* generate FSE decoding table for one symbol (ll, ml or off)
* cannot fail if input is valid =>
* all inputs are presumed validated at this stage */
FORCE_INLINE_TEMPLATE
void ZSTD_buildFSETable_body(ZSTD_seqSymbol* dt,
const short* normalizedCounter, unsigned maxSymbolValue,
const U32* baseValue, const U8* nbAdditionalBits,
unsigned tableLog, void* wksp, size_t wkspSize)
{
ZSTD_seqSymbol* const tableDecode = dt+1;
U32 const maxSV1 = maxSymbolValue + 1;
U32 const tableSize = 1 << tableLog;
U16* symbolNext = (U16*)wksp;
BYTE* spread = (BYTE*)(symbolNext + MaxSeq + 1);
U32 highThreshold = tableSize - 1;
/* Sanity Checks */
assert(maxSymbolValue <= MaxSeq);
assert(tableLog <= MaxFSELog);
assert(wkspSize >= ZSTD_BUILD_FSE_TABLE_WKSP_SIZE);
(void)wkspSize;
/* Init, lay down lowprob symbols */
{ ZSTD_seqSymbol_header DTableH;
DTableH.tableLog = tableLog;
DTableH.fastMode = 1;
{ S16 const largeLimit= (S16)(1 << (tableLog-1));
U32 s;
for (s=0; s<maxSV1; s++) {
if (normalizedCounter[s]==-1) {
tableDecode[highThreshold--].baseValue = s;
symbolNext[s] = 1;
} else {
if (normalizedCounter[s] >= largeLimit) DTableH.fastMode=0;
assert(normalizedCounter[s]>=0);
symbolNext[s] = (U16)normalizedCounter[s];
} } }
ZSTD_memcpy(dt, &DTableH, sizeof(DTableH));
}
/* Spread symbols */
assert(tableSize <= 512);
/* Specialized symbol spreading for the case when there are
* no low probability (-1 count) symbols. When compressing
* small blocks we avoid low probability symbols to hit this
* case, since header decoding speed matters more.
*/
if (highThreshold == tableSize - 1) {
size_t const tableMask = tableSize-1;
size_t const step = FSE_TABLESTEP(tableSize);
/* First lay down the symbols in order.
* We use a uint64_t to lay down 8 bytes at a time. This reduces branch
* misses since small blocks generally have small table logs, so nearly
* all symbols have counts <= 8. We ensure we have 8 bytes at the end of
* our buffer to handle the over-write.
*/
{
U64 const add = 0x0101010101010101ull;
size_t pos = 0;
U64 sv = 0;
U32 s;
for (s=0; s<maxSV1; ++s, sv += add) {
int i;
int const n = normalizedCounter[s];
MEM_write64(spread + pos, sv);
for (i = 8; i < n; i += 8) {
MEM_write64(spread + pos + i, sv);
}
pos += n;
}
}
/* Now we spread those positions across the table.
* The benefit of doing it in two stages is that we avoid the the
* variable size inner loop, which caused lots of branch misses.
* Now we can run through all the positions without any branch misses.
* We unroll the loop twice, since that is what emperically worked best.
*/
{
size_t position = 0;
size_t s;
size_t const unroll = 2;
assert(tableSize % unroll == 0); /* FSE_MIN_TABLELOG is 5 */
for (s = 0; s < (size_t)tableSize; s += unroll) {
size_t u;
for (u = 0; u < unroll; ++u) {
size_t const uPosition = (position + (u * step)) & tableMask;
tableDecode[uPosition].baseValue = spread[s + u];
}
position = (position + (unroll * step)) & tableMask;
}
assert(position == 0);
}
} else {
U32 const tableMask = tableSize-1;
U32 const step = FSE_TABLESTEP(tableSize);
U32 s, position = 0;
for (s=0; s<maxSV1; s++) {
int i;
int const n = normalizedCounter[s];
for (i=0; i<n; i++) {
tableDecode[position].baseValue = s;
position = (position + step) & tableMask;
while (position > highThreshold) position = (position + step) & tableMask; /* lowprob area */
} }
assert(position == 0); /* position must reach all cells once, otherwise normalizedCounter is incorrect */
}
/* Build Decoding table */
{
U32 u;
for (u=0; u<tableSize; u++) {
U32 const symbol = tableDecode[u].baseValue;
U32 const nextState = symbolNext[symbol]++;
tableDecode[u].nbBits = (BYTE) (tableLog - BIT_highbit32(nextState) );
tableDecode[u].nextState = (U16) ( (nextState << tableDecode[u].nbBits) - tableSize);
assert(nbAdditionalBits[symbol] < 255);
tableDecode[u].nbAdditionalBits = nbAdditionalBits[symbol];
tableDecode[u].baseValue = baseValue[symbol];
}
}
}
/* Avoids the FORCE_INLINE of the _body() function. */
static void ZSTD_buildFSETable_body_default(ZSTD_seqSymbol* dt,
const short* normalizedCounter, unsigned maxSymbolValue,
const U32* baseValue, const U8* nbAdditionalBits,
unsigned tableLog, void* wksp, size_t wkspSize)
{
ZSTD_buildFSETable_body(dt, normalizedCounter, maxSymbolValue,
baseValue, nbAdditionalBits, tableLog, wksp, wkspSize);
}
#if DYNAMIC_BMI2
BMI2_TARGET_ATTRIBUTE static void ZSTD_buildFSETable_body_bmi2(ZSTD_seqSymbol* dt,
const short* normalizedCounter, unsigned maxSymbolValue,
const U32* baseValue, const U8* nbAdditionalBits,
unsigned tableLog, void* wksp, size_t wkspSize)
{
ZSTD_buildFSETable_body(dt, normalizedCounter, maxSymbolValue,
baseValue, nbAdditionalBits, tableLog, wksp, wkspSize);
}
#endif
void ZSTD_buildFSETable(ZSTD_seqSymbol* dt,
const short* normalizedCounter, unsigned maxSymbolValue,
const U32* baseValue, const U8* nbAdditionalBits,
unsigned tableLog, void* wksp, size_t wkspSize, int bmi2)
{
#if DYNAMIC_BMI2
if (bmi2) {
ZSTD_buildFSETable_body_bmi2(dt, normalizedCounter, maxSymbolValue,
baseValue, nbAdditionalBits, tableLog, wksp, wkspSize);
return;
}
#endif
(void)bmi2;
ZSTD_buildFSETable_body_default(dt, normalizedCounter, maxSymbolValue,
baseValue, nbAdditionalBits, tableLog, wksp, wkspSize);
}
/*! ZSTD_buildSeqTable() :
* @return : nb bytes read from src,
* or an error code if it fails */
static size_t ZSTD_buildSeqTable(ZSTD_seqSymbol* DTableSpace, const ZSTD_seqSymbol** DTablePtr,
symbolEncodingType_e type, unsigned max, U32 maxLog,
const void* src, size_t srcSize,
const U32* baseValue, const U8* nbAdditionalBits,
const ZSTD_seqSymbol* defaultTable, U32 flagRepeatTable,
int ddictIsCold, int nbSeq, U32* wksp, size_t wkspSize,
int bmi2)
{
switch(type)
{
case set_rle :
RETURN_ERROR_IF(!srcSize, srcSize_wrong, "");
RETURN_ERROR_IF((*(const BYTE*)src) > max, corruption_detected, "");
{ U32 const symbol = *(const BYTE*)src;
U32 const baseline = baseValue[symbol];
U8 const nbBits = nbAdditionalBits[symbol];
ZSTD_buildSeqTable_rle(DTableSpace, baseline, nbBits);
}
*DTablePtr = DTableSpace;
return 1;
case set_basic :
*DTablePtr = defaultTable;
return 0;
case set_repeat:
RETURN_ERROR_IF(!flagRepeatTable, corruption_detected, "");
/* prefetch FSE table if used */
if (ddictIsCold && (nbSeq > 24 /* heuristic */)) {
const void* const pStart = *DTablePtr;
size_t const pSize = sizeof(ZSTD_seqSymbol) * (SEQSYMBOL_TABLE_SIZE(maxLog));
PREFETCH_AREA(pStart, pSize);
}
return 0;
case set_compressed :
{ unsigned tableLog;
S16 norm[MaxSeq+1];
size_t const headerSize = FSE_readNCount(norm, &max, &tableLog, src, srcSize);
RETURN_ERROR_IF(FSE_isError(headerSize), corruption_detected, "");
RETURN_ERROR_IF(tableLog > maxLog, corruption_detected, "");
ZSTD_buildFSETable(DTableSpace, norm, max, baseValue, nbAdditionalBits, tableLog, wksp, wkspSize, bmi2);
*DTablePtr = DTableSpace;
return headerSize;
}
default :
assert(0);
RETURN_ERROR(GENERIC, "impossible");
}
}
size_t ZSTD_decodeSeqHeaders(ZSTD_DCtx* dctx, int* nbSeqPtr,
const void* src, size_t srcSize)
{
const BYTE* const istart = (const BYTE*)src;
const BYTE* const iend = istart + srcSize;
const BYTE* ip = istart;
int nbSeq;
DEBUGLOG(5, "ZSTD_decodeSeqHeaders");
/* check */
RETURN_ERROR_IF(srcSize < MIN_SEQUENCES_SIZE, srcSize_wrong, "");
/* SeqHead */
nbSeq = *ip++;
if (!nbSeq) {
*nbSeqPtr=0;
RETURN_ERROR_IF(srcSize != 1, srcSize_wrong, "");
return 1;
}
if (nbSeq > 0x7F) {
if (nbSeq == 0xFF) {
RETURN_ERROR_IF(ip+2 > iend, srcSize_wrong, "");
nbSeq = MEM_readLE16(ip) + LONGNBSEQ;
ip+=2;
} else {
RETURN_ERROR_IF(ip >= iend, srcSize_wrong, "");
nbSeq = ((nbSeq-0x80)<<8) + *ip++;
}
}
*nbSeqPtr = nbSeq;
/* FSE table descriptors */
RETURN_ERROR_IF(ip+1 > iend, srcSize_wrong, ""); /* minimum possible size: 1 byte for symbol encoding types */
{ symbolEncodingType_e const LLtype = (symbolEncodingType_e)(*ip >> 6);
symbolEncodingType_e const OFtype = (symbolEncodingType_e)((*ip >> 4) & 3);
symbolEncodingType_e const MLtype = (symbolEncodingType_e)((*ip >> 2) & 3);
ip++;
/* Build DTables */
{ size_t const llhSize = ZSTD_buildSeqTable(dctx->entropy.LLTable, &dctx->LLTptr,
LLtype, MaxLL, LLFSELog,
ip, iend-ip,
LL_base, LL_bits,
LL_defaultDTable, dctx->fseEntropy,
dctx->ddictIsCold, nbSeq,
dctx->workspace, sizeof(dctx->workspace),
ZSTD_DCtx_get_bmi2(dctx));
RETURN_ERROR_IF(ZSTD_isError(llhSize), corruption_detected, "ZSTD_buildSeqTable failed");
ip += llhSize;
}
{ size_t const ofhSize = ZSTD_buildSeqTable(dctx->entropy.OFTable, &dctx->OFTptr,
OFtype, MaxOff, OffFSELog,
ip, iend-ip,
OF_base, OF_bits,
OF_defaultDTable, dctx->fseEntropy,
dctx->ddictIsCold, nbSeq,
dctx->workspace, sizeof(dctx->workspace),
ZSTD_DCtx_get_bmi2(dctx));
RETURN_ERROR_IF(ZSTD_isError(ofhSize), corruption_detected, "ZSTD_buildSeqTable failed");
ip += ofhSize;
}
{ size_t const mlhSize = ZSTD_buildSeqTable(dctx->entropy.MLTable, &dctx->MLTptr,
MLtype, MaxML, MLFSELog,
ip, iend-ip,
ML_base, ML_bits,
ML_defaultDTable, dctx->fseEntropy,
dctx->ddictIsCold, nbSeq,
dctx->workspace, sizeof(dctx->workspace),
ZSTD_DCtx_get_bmi2(dctx));
RETURN_ERROR_IF(ZSTD_isError(mlhSize), corruption_detected, "ZSTD_buildSeqTable failed");
ip += mlhSize;
}
}
return ip-istart;
}
typedef struct {
size_t litLength;
size_t matchLength;
size_t offset;
} seq_t;
typedef struct {
size_t state;
const ZSTD_seqSymbol* table;
} ZSTD_fseState;
typedef struct {
BIT_DStream_t DStream;
ZSTD_fseState stateLL;
ZSTD_fseState stateOffb;
ZSTD_fseState stateML;
size_t prevOffset[ZSTD_REP_NUM];
} seqState_t;
/*! ZSTD_overlapCopy8() :
* Copies 8 bytes from ip to op and updates op and ip where ip <= op.
* If the offset is < 8 then the offset is spread to at least 8 bytes.
*
* Precondition: *ip <= *op
* Postcondition: *op - *op >= 8
*/
HINT_INLINE void ZSTD_overlapCopy8(BYTE** op, BYTE const** ip, size_t offset) {
assert(*ip <= *op);
if (offset < 8) {
/* close range match, overlap */
static const U32 dec32table[] = { 0, 1, 2, 1, 4, 4, 4, 4 }; /* added */
static const int dec64table[] = { 8, 8, 8, 7, 8, 9,10,11 }; /* subtracted */
int const sub2 = dec64table[offset];
(*op)[0] = (*ip)[0];
(*op)[1] = (*ip)[1];
(*op)[2] = (*ip)[2];
(*op)[3] = (*ip)[3];
*ip += dec32table[offset];
ZSTD_copy4(*op+4, *ip);
*ip -= sub2;
} else {
ZSTD_copy8(*op, *ip);
}
*ip += 8;
*op += 8;
assert(*op - *ip >= 8);
}
/*! ZSTD_safecopy() :
* Specialized version of memcpy() that is allowed to READ up to WILDCOPY_OVERLENGTH past the input buffer
* and write up to 16 bytes past oend_w (op >= oend_w is allowed).
* This function is only called in the uncommon case where the sequence is near the end of the block. It
* should be fast for a single long sequence, but can be slow for several short sequences.
*
* @param ovtype controls the overlap detection
* - ZSTD_no_overlap: The source and destination are guaranteed to be at least WILDCOPY_VECLEN bytes apart.
* - ZSTD_overlap_src_before_dst: The src and dst may overlap and may be any distance apart.
* The src buffer must be before the dst buffer.
*/
static void ZSTD_safecopy(BYTE* op, const BYTE* const oend_w, BYTE const* ip, ptrdiff_t length, ZSTD_overlap_e ovtype) {
ptrdiff_t const diff = op - ip;
BYTE* const oend = op + length;
assert((ovtype == ZSTD_no_overlap && (diff <= -8 || diff >= 8 || op >= oend_w)) ||
(ovtype == ZSTD_overlap_src_before_dst && diff >= 0));
if (length < 8) {
/* Handle short lengths. */
while (op < oend) *op++ = *ip++;
return;
}
if (ovtype == ZSTD_overlap_src_before_dst) {
/* Copy 8 bytes and ensure the offset >= 8 when there can be overlap. */
assert(length >= 8);
ZSTD_overlapCopy8(&op, &ip, diff);
length -= 8;
assert(op - ip >= 8);
assert(op <= oend);
}
if (oend <= oend_w) {
/* No risk of overwrite. */
ZSTD_wildcopy(op, ip, length, ovtype);
return;
}
if (op <= oend_w) {
/* Wildcopy until we get close to the end. */
assert(oend > oend_w);
ZSTD_wildcopy(op, ip, oend_w - op, ovtype);
ip += oend_w - op;
op += oend_w - op;
}
/* Handle the leftovers. */
while (op < oend) *op++ = *ip++;
}
/* ZSTD_safecopyDstBeforeSrc():
* This version allows overlap with dst before src, or handles the non-overlap case with dst after src
* Kept separate from more common ZSTD_safecopy case to avoid performance impact to the safecopy common case */
static void ZSTD_safecopyDstBeforeSrc(BYTE* op, BYTE const* ip, ptrdiff_t length) {
ptrdiff_t const diff = op - ip;
BYTE* const oend = op + length;
if (length < 8 || diff > -8) {
/* Handle short lengths, close overlaps, and dst not before src. */
while (op < oend) *op++ = *ip++;
return;
}
if (op <= oend - WILDCOPY_OVERLENGTH && diff < -WILDCOPY_VECLEN) {
ZSTD_wildcopy(op, ip, oend - WILDCOPY_OVERLENGTH - op, ZSTD_no_overlap);
ip += oend - WILDCOPY_OVERLENGTH - op;
op += oend - WILDCOPY_OVERLENGTH - op;
}
/* Handle the leftovers. */
while (op < oend) *op++ = *ip++;
}
/* ZSTD_execSequenceEnd():
* This version handles cases that are near the end of the output buffer. It requires
* more careful checks to make sure there is no overflow. By separating out these hard
* and unlikely cases, we can speed up the common cases.
*
* NOTE: This function needs to be fast for a single long sequence, but doesn't need
* to be optimized for many small sequences, since those fall into ZSTD_execSequence().
*/
FORCE_NOINLINE
size_t ZSTD_execSequenceEnd(BYTE* op,
BYTE* const oend, seq_t sequence,
const BYTE** litPtr, const BYTE* const litLimit,
const BYTE* const prefixStart, const BYTE* const virtualStart, const BYTE* const dictEnd)
{
BYTE* const oLitEnd = op + sequence.litLength;
size_t const sequenceLength = sequence.litLength + sequence.matchLength;
const BYTE* const iLitEnd = *litPtr + sequence.litLength;
const BYTE* match = oLitEnd - sequence.offset;
BYTE* const oend_w = oend - WILDCOPY_OVERLENGTH;
/* bounds checks : careful of address space overflow in 32-bit mode */
RETURN_ERROR_IF(sequenceLength > (size_t)(oend - op), dstSize_tooSmall, "last match must fit within dstBuffer");
RETURN_ERROR_IF(sequence.litLength > (size_t)(litLimit - *litPtr), corruption_detected, "try to read beyond literal buffer");
assert(op < op + sequenceLength);
assert(oLitEnd < op + sequenceLength);
/* copy literals */
ZSTD_safecopy(op, oend_w, *litPtr, sequence.litLength, ZSTD_no_overlap);
op = oLitEnd;
*litPtr = iLitEnd;
/* copy Match */
if (sequence.offset > (size_t)(oLitEnd - prefixStart)) {
/* offset beyond prefix */
RETURN_ERROR_IF(sequence.offset > (size_t)(oLitEnd - virtualStart), corruption_detected, "");
match = dictEnd - (prefixStart - match);
if (match + sequence.matchLength <= dictEnd) {
ZSTD_memmove(oLitEnd, match, sequence.matchLength);
return sequenceLength;
}
/* span extDict & currentPrefixSegment */
{ size_t const length1 = dictEnd - match;
ZSTD_memmove(oLitEnd, match, length1);
op = oLitEnd + length1;
sequence.matchLength -= length1;
match = prefixStart;
}
}
ZSTD_safecopy(op, oend_w, match, sequence.matchLength, ZSTD_overlap_src_before_dst);
return sequenceLength;
}
/* ZSTD_execSequenceEndSplitLitBuffer():
* This version is intended to be used during instances where the litBuffer is still split. It is kept separate to avoid performance impact for the good case.
*/
FORCE_NOINLINE
size_t ZSTD_execSequenceEndSplitLitBuffer(BYTE* op,
BYTE* const oend, const BYTE* const oend_w, seq_t sequence,
const BYTE** litPtr, const BYTE* const litLimit,
const BYTE* const prefixStart, const BYTE* const virtualStart, const BYTE* const dictEnd)
{
BYTE* const oLitEnd = op + sequence.litLength;
size_t const sequenceLength = sequence.litLength + sequence.matchLength;
const BYTE* const iLitEnd = *litPtr + sequence.litLength;
const BYTE* match = oLitEnd - sequence.offset;
/* bounds checks : careful of address space overflow in 32-bit mode */
RETURN_ERROR_IF(sequenceLength > (size_t)(oend - op), dstSize_tooSmall, "last match must fit within dstBuffer");
RETURN_ERROR_IF(sequence.litLength > (size_t)(litLimit - *litPtr), corruption_detected, "try to read beyond literal buffer");
assert(op < op + sequenceLength);
assert(oLitEnd < op + sequenceLength);
/* copy literals */
RETURN_ERROR_IF(op > *litPtr && op < *litPtr + sequence.litLength, dstSize_tooSmall, "output should not catch up to and overwrite literal buffer");
ZSTD_safecopyDstBeforeSrc(op, *litPtr, sequence.litLength);
op = oLitEnd;
*litPtr = iLitEnd;
/* copy Match */
if (sequence.offset > (size_t)(oLitEnd - prefixStart)) {
/* offset beyond prefix */
RETURN_ERROR_IF(sequence.offset > (size_t)(oLitEnd - virtualStart), corruption_detected, "");
match = dictEnd - (prefixStart - match);
if (match + sequence.matchLength <= dictEnd) {
ZSTD_memmove(oLitEnd, match, sequence.matchLength);
return sequenceLength;
}
/* span extDict & currentPrefixSegment */
{ size_t const length1 = dictEnd - match;
ZSTD_memmove(oLitEnd, match, length1);
op = oLitEnd + length1;
sequence.matchLength -= length1;
match = prefixStart;
}
}
ZSTD_safecopy(op, oend_w, match, sequence.matchLength, ZSTD_overlap_src_before_dst);
return sequenceLength;
}
HINT_INLINE
size_t ZSTD_execSequence(BYTE* op,
BYTE* const oend, seq_t sequence,
const BYTE** litPtr, const BYTE* const litLimit,
const BYTE* const prefixStart, const BYTE* const virtualStart, const BYTE* const dictEnd)
{
BYTE* const oLitEnd = op + sequence.litLength;
size_t const sequenceLength = sequence.litLength + sequence.matchLength;
BYTE* const oMatchEnd = op + sequenceLength; /* risk : address space overflow (32-bits) */
BYTE* const oend_w = oend - WILDCOPY_OVERLENGTH; /* risk : address space underflow on oend=NULL */
const BYTE* const iLitEnd = *litPtr + sequence.litLength;
const BYTE* match = oLitEnd - sequence.offset;
assert(op != NULL /* Precondition */);
assert(oend_w < oend /* No underflow */);
/* Handle edge cases in a slow path:
* - Read beyond end of literals
* - Match end is within WILDCOPY_OVERLIMIT of oend
* - 32-bit mode and the match length overflows
*/
if (UNLIKELY(
iLitEnd > litLimit ||
oMatchEnd > oend_w ||
(MEM_32bits() && (size_t)(oend - op) < sequenceLength + WILDCOPY_OVERLENGTH)))
return ZSTD_execSequenceEnd(op, oend, sequence, litPtr, litLimit, prefixStart, virtualStart, dictEnd);
/* Assumptions (everything else goes into ZSTD_execSequenceEnd()) */
assert(op <= oLitEnd /* No overflow */);
assert(oLitEnd < oMatchEnd /* Non-zero match & no overflow */);
assert(oMatchEnd <= oend /* No underflow */);
assert(iLitEnd <= litLimit /* Literal length is in bounds */);
assert(oLitEnd <= oend_w /* Can wildcopy literals */);
assert(oMatchEnd <= oend_w /* Can wildcopy matches */);
/* Copy Literals:
* Split out litLength <= 16 since it is nearly always true. +1.6% on gcc-9.
* We likely don't need the full 32-byte wildcopy.
*/
assert(WILDCOPY_OVERLENGTH >= 16);
ZSTD_copy16(op, (*litPtr));
if (UNLIKELY(sequence.litLength > 16)) {
ZSTD_wildcopy(op + 16, (*litPtr) + 16, sequence.litLength - 16, ZSTD_no_overlap);
}
op = oLitEnd;
*litPtr = iLitEnd; /* update for next sequence */
/* Copy Match */
if (sequence.offset > (size_t)(oLitEnd - prefixStart)) {
/* offset beyond prefix -> go into extDict */
RETURN_ERROR_IF(UNLIKELY(sequence.offset > (size_t)(oLitEnd - virtualStart)), corruption_detected, "");
match = dictEnd + (match - prefixStart);
if (match + sequence.matchLength <= dictEnd) {
ZSTD_memmove(oLitEnd, match, sequence.matchLength);
return sequenceLength;
}
/* span extDict & currentPrefixSegment */
{ size_t const length1 = dictEnd - match;
ZSTD_memmove(oLitEnd, match, length1);
op = oLitEnd + length1;
sequence.matchLength -= length1;
match = prefixStart;
}
}
/* Match within prefix of 1 or more bytes */
assert(op <= oMatchEnd);
assert(oMatchEnd <= oend_w);
assert(match >= prefixStart);
assert(sequence.matchLength >= 1);
/* Nearly all offsets are >= WILDCOPY_VECLEN bytes, which means we can use wildcopy
* without overlap checking.
*/
if (LIKELY(sequence.offset >= WILDCOPY_VECLEN)) {
/* We bet on a full wildcopy for matches, since we expect matches to be
* longer than literals (in general). In silesia, ~10% of matches are longer
* than 16 bytes.
*/
ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength, ZSTD_no_overlap);
return sequenceLength;
}
assert(sequence.offset < WILDCOPY_VECLEN);
/* Copy 8 bytes and spread the offset to be >= 8. */
ZSTD_overlapCopy8(&op, &match, sequence.offset);
/* If the match length is > 8 bytes, then continue with the wildcopy. */
if (sequence.matchLength > 8) {
assert(op < oMatchEnd);
ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength - 8, ZSTD_overlap_src_before_dst);
}
return sequenceLength;
}
HINT_INLINE
size_t ZSTD_execSequenceSplitLitBuffer(BYTE* op,
BYTE* const oend, const BYTE* const oend_w, seq_t sequence,
const BYTE** litPtr, const BYTE* const litLimit,
const BYTE* const prefixStart, const BYTE* const virtualStart, const BYTE* const dictEnd)
{
BYTE* const oLitEnd = op + sequence.litLength;
size_t const sequenceLength = sequence.litLength + sequence.matchLength;
BYTE* const oMatchEnd = op + sequenceLength; /* risk : address space overflow (32-bits) */
const BYTE* const iLitEnd = *litPtr + sequence.litLength;
const BYTE* match = oLitEnd - sequence.offset;
assert(op != NULL /* Precondition */);
assert(oend_w < oend /* No underflow */);
/* Handle edge cases in a slow path:
* - Read beyond end of literals
* - Match end is within WILDCOPY_OVERLIMIT of oend
* - 32-bit mode and the match length overflows
*/
if (UNLIKELY(
iLitEnd > litLimit ||
oMatchEnd > oend_w ||
(MEM_32bits() && (size_t)(oend - op) < sequenceLength + WILDCOPY_OVERLENGTH)))
return ZSTD_execSequenceEndSplitLitBuffer(op, oend, oend_w, sequence, litPtr, litLimit, prefixStart, virtualStart, dictEnd);
/* Assumptions (everything else goes into ZSTD_execSequenceEnd()) */
assert(op <= oLitEnd /* No overflow */);
assert(oLitEnd < oMatchEnd /* Non-zero match & no overflow */);
assert(oMatchEnd <= oend /* No underflow */);
assert(iLitEnd <= litLimit /* Literal length is in bounds */);
assert(oLitEnd <= oend_w /* Can wildcopy literals */);
assert(oMatchEnd <= oend_w /* Can wildcopy matches */);
/* Copy Literals:
* Split out litLength <= 16 since it is nearly always true. +1.6% on gcc-9.
* We likely don't need the full 32-byte wildcopy.
*/
assert(WILDCOPY_OVERLENGTH >= 16);
ZSTD_copy16(op, (*litPtr));
if (UNLIKELY(sequence.litLength > 16)) {
ZSTD_wildcopy(op+16, (*litPtr)+16, sequence.litLength-16, ZSTD_no_overlap);
}
op = oLitEnd;
*litPtr = iLitEnd; /* update for next sequence */
/* Copy Match */
if (sequence.offset > (size_t)(oLitEnd - prefixStart)) {
/* offset beyond prefix -> go into extDict */
RETURN_ERROR_IF(UNLIKELY(sequence.offset > (size_t)(oLitEnd - virtualStart)), corruption_detected, "");
match = dictEnd + (match - prefixStart);
if (match + sequence.matchLength <= dictEnd) {
ZSTD_memmove(oLitEnd, match, sequence.matchLength);
return sequenceLength;
}
/* span extDict & currentPrefixSegment */
{ size_t const length1 = dictEnd - match;
ZSTD_memmove(oLitEnd, match, length1);
op = oLitEnd + length1;
sequence.matchLength -= length1;
match = prefixStart;
} }
/* Match within prefix of 1 or more bytes */
assert(op <= oMatchEnd);
assert(oMatchEnd <= oend_w);
assert(match >= prefixStart);
assert(sequence.matchLength >= 1);
/* Nearly all offsets are >= WILDCOPY_VECLEN bytes, which means we can use wildcopy
* without overlap checking.
*/
if (LIKELY(sequence.offset >= WILDCOPY_VECLEN)) {
/* We bet on a full wildcopy for matches, since we expect matches to be
* longer than literals (in general). In silesia, ~10% of matches are longer
* than 16 bytes.
*/
ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength, ZSTD_no_overlap);
return sequenceLength;
}
assert(sequence.offset < WILDCOPY_VECLEN);
/* Copy 8 bytes and spread the offset to be >= 8. */
ZSTD_overlapCopy8(&op, &match, sequence.offset);
/* If the match length is > 8 bytes, then continue with the wildcopy. */
if (sequence.matchLength > 8) {
assert(op < oMatchEnd);
ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength-8, ZSTD_overlap_src_before_dst);
}
return sequenceLength;
}
static void
ZSTD_initFseState(ZSTD_fseState* DStatePtr, BIT_DStream_t* bitD, const ZSTD_seqSymbol* dt)
{
const void* ptr = dt;
const ZSTD_seqSymbol_header* const DTableH = (const ZSTD_seqSymbol_header*)ptr;
DStatePtr->state = BIT_readBits(bitD, DTableH->tableLog);
DEBUGLOG(6, "ZSTD_initFseState : val=%u using %u bits",
(U32)DStatePtr->state, DTableH->tableLog);
BIT_reloadDStream(bitD);
DStatePtr->table = dt + 1;
}
FORCE_INLINE_TEMPLATE void
ZSTD_updateFseStateWithDInfo(ZSTD_fseState* DStatePtr, BIT_DStream_t* bitD, U16 nextState, U32 nbBits)
{
size_t const lowBits = BIT_readBits(bitD, nbBits);
DStatePtr->state = nextState + lowBits;
}
/* We need to add at most (ZSTD_WINDOWLOG_MAX_32 - 1) bits to read the maximum
* offset bits. But we can only read at most (STREAM_ACCUMULATOR_MIN_32 - 1)
* bits before reloading. This value is the maximum number of bytes we read
* after reloading when we are decoding long offsets.
*/
#define LONG_OFFSETS_MAX_EXTRA_BITS_32 \
(ZSTD_WINDOWLOG_MAX_32 > STREAM_ACCUMULATOR_MIN_32 \
? ZSTD_WINDOWLOG_MAX_32 - STREAM_ACCUMULATOR_MIN_32 \
: 0)
typedef enum { ZSTD_lo_isRegularOffset, ZSTD_lo_isLongOffset=1 } ZSTD_longOffset_e;
FORCE_INLINE_TEMPLATE seq_t
ZSTD_decodeSequence(seqState_t* seqState, const ZSTD_longOffset_e longOffsets)
{
seq_t seq;
const ZSTD_seqSymbol* const llDInfo = seqState->stateLL.table + seqState->stateLL.state;
const ZSTD_seqSymbol* const mlDInfo = seqState->stateML.table + seqState->stateML.state;
const ZSTD_seqSymbol* const ofDInfo = seqState->stateOffb.table + seqState->stateOffb.state;
seq.matchLength = mlDInfo->baseValue;
seq.litLength = llDInfo->baseValue;
{ U32 const ofBase = ofDInfo->baseValue;
BYTE const llBits = llDInfo->nbAdditionalBits;
BYTE const mlBits = mlDInfo->nbAdditionalBits;
BYTE const ofBits = ofDInfo->nbAdditionalBits;
BYTE const totalBits = llBits+mlBits+ofBits;
U16 const llNext = llDInfo->nextState;
U16 const mlNext = mlDInfo->nextState;
U16 const ofNext = ofDInfo->nextState;
U32 const llnbBits = llDInfo->nbBits;
U32 const mlnbBits = mlDInfo->nbBits;
U32 const ofnbBits = ofDInfo->nbBits;
/*
* As gcc has better branch and block analyzers, sometimes it is only
* valuable to mark likelyness for clang, it gives around 3-4% of
* performance.
*/
/* sequence */
{ size_t offset;
#if defined(__clang__)
if (LIKELY(ofBits > 1)) {
#else
if (ofBits > 1) {
#endif
ZSTD_STATIC_ASSERT(ZSTD_lo_isLongOffset == 1);
ZSTD_STATIC_ASSERT(LONG_OFFSETS_MAX_EXTRA_BITS_32 == 5);
assert(ofBits <= MaxOff);
if (MEM_32bits() && longOffsets && (ofBits >= STREAM_ACCUMULATOR_MIN_32)) {
U32 const extraBits = ofBits - MIN(ofBits, 32 - seqState->DStream.bitsConsumed);
offset = ofBase + (BIT_readBitsFast(&seqState->DStream, ofBits - extraBits) << extraBits);
BIT_reloadDStream(&seqState->DStream);
if (extraBits) offset += BIT_readBitsFast(&seqState->DStream, extraBits);
assert(extraBits <= LONG_OFFSETS_MAX_EXTRA_BITS_32); /* to avoid another reload */
} else {
offset = ofBase + BIT_readBitsFast(&seqState->DStream, ofBits/*>0*/); /* <= (ZSTD_WINDOWLOG_MAX-1) bits */
if (MEM_32bits()) BIT_reloadDStream(&seqState->DStream);
}
seqState->prevOffset[2] = seqState->prevOffset[1];
seqState->prevOffset[1] = seqState->prevOffset[0];
seqState->prevOffset[0] = offset;
} else {
U32 const ll0 = (llDInfo->baseValue == 0);
if (LIKELY((ofBits == 0))) {
offset = seqState->prevOffset[ll0];
seqState->prevOffset[1] = seqState->prevOffset[!ll0];
seqState->prevOffset[0] = offset;
} else {
offset = ofBase + ll0 + BIT_readBitsFast(&seqState->DStream, 1);
{ size_t temp = (offset==3) ? seqState->prevOffset[0] - 1 : seqState->prevOffset[offset];
temp += !temp; /* 0 is not valid; input is corrupted; force offset to 1 */
if (offset != 1) seqState->prevOffset[2] = seqState->prevOffset[1];
seqState->prevOffset[1] = seqState->prevOffset[0];
seqState->prevOffset[0] = offset = temp;
} } }
seq.offset = offset;
}
#if defined(__clang__)
if (UNLIKELY(mlBits > 0))
#else
if (mlBits > 0)
#endif
seq.matchLength += BIT_readBitsFast(&seqState->DStream, mlBits/*>0*/);
if (MEM_32bits() && (mlBits+llBits >= STREAM_ACCUMULATOR_MIN_32-LONG_OFFSETS_MAX_EXTRA_BITS_32))
BIT_reloadDStream(&seqState->DStream);
if (MEM_64bits() && UNLIKELY(totalBits >= STREAM_ACCUMULATOR_MIN_64-(LLFSELog+MLFSELog+OffFSELog)))
BIT_reloadDStream(&seqState->DStream);
/* Ensure there are enough bits to read the rest of data in 64-bit mode. */
ZSTD_STATIC_ASSERT(16+LLFSELog+MLFSELog+OffFSELog < STREAM_ACCUMULATOR_MIN_64);
#if defined(__clang__)
if (UNLIKELY(llBits > 0))
#else
if (llBits > 0)
#endif
seq.litLength += BIT_readBitsFast(&seqState->DStream, llBits/*>0*/);
if (MEM_32bits())
BIT_reloadDStream(&seqState->DStream);
DEBUGLOG(6, "seq: litL=%u, matchL=%u, offset=%u",
(U32)seq.litLength, (U32)seq.matchLength, (U32)seq.offset);
ZSTD_updateFseStateWithDInfo(&seqState->stateLL, &seqState->DStream, llNext, llnbBits); /* <= 9 bits */
ZSTD_updateFseStateWithDInfo(&seqState->stateML, &seqState->DStream, mlNext, mlnbBits); /* <= 9 bits */
if (MEM_32bits()) BIT_reloadDStream(&seqState->DStream); /* <= 18 bits */
ZSTD_updateFseStateWithDInfo(&seqState->stateOffb, &seqState->DStream, ofNext, ofnbBits); /* <= 8 bits */
}
return seq;
}
#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
MEM_STATIC int ZSTD_dictionaryIsActive(ZSTD_DCtx const* dctx, BYTE const* prefixStart, BYTE const* oLitEnd)
{
size_t const windowSize = dctx->fParams.windowSize;
/* No dictionary used. */
if (dctx->dictContentEndForFuzzing == NULL) return 0;
/* Dictionary is our prefix. */
if (prefixStart == dctx->dictContentBeginForFuzzing) return 1;
/* Dictionary is not our ext-dict. */
if (dctx->dictEnd != dctx->dictContentEndForFuzzing) return 0;
/* Dictionary is not within our window size. */
if ((size_t)(oLitEnd - prefixStart) >= windowSize) return 0;
/* Dictionary is active. */
return 1;
}
MEM_STATIC void ZSTD_assertValidSequence(
ZSTD_DCtx const* dctx,
BYTE const* op, BYTE const* oend,
seq_t const seq,
BYTE const* prefixStart, BYTE const* virtualStart)
{
#if DEBUGLEVEL >= 1
size_t const windowSize = dctx->fParams.windowSize;
size_t const sequenceSize = seq.litLength + seq.matchLength;
BYTE const* const oLitEnd = op + seq.litLength;
DEBUGLOG(6, "Checking sequence: litL=%u matchL=%u offset=%u",
(U32)seq.litLength, (U32)seq.matchLength, (U32)seq.offset);
assert(op <= oend);
assert((size_t)(oend - op) >= sequenceSize);
assert(sequenceSize <= ZSTD_BLOCKSIZE_MAX);
if (ZSTD_dictionaryIsActive(dctx, prefixStart, oLitEnd)) {
size_t const dictSize = (size_t)((char const*)dctx->dictContentEndForFuzzing - (char const*)dctx->dictContentBeginForFuzzing);
/* Offset must be within the dictionary. */
assert(seq.offset <= (size_t)(oLitEnd - virtualStart));
assert(seq.offset <= windowSize + dictSize);
} else {
/* Offset must be within our window. */
assert(seq.offset <= windowSize);
}
#else
(void)dctx, (void)op, (void)oend, (void)seq, (void)prefixStart, (void)virtualStart;
#endif
}
#endif
#ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG
FORCE_INLINE_TEMPLATE size_t
DONT_VECTORIZE
ZSTD_decompressSequences_bodySplitLitBuffer( ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
const BYTE* ip = (const BYTE*)seqStart;
const BYTE* const iend = ip + seqSize;
BYTE* const ostart = (BYTE*)dst;
BYTE* const oend = ostart + maxDstSize;
BYTE* op = ostart;
const BYTE* litPtr = dctx->litPtr;
const BYTE* litBufferEnd = dctx->litBufferEnd;
const BYTE* const prefixStart = (const BYTE*) (dctx->prefixStart);
const BYTE* const vBase = (const BYTE*) (dctx->virtualStart);
const BYTE* const dictEnd = (const BYTE*) (dctx->dictEnd);
DEBUGLOG(5, "ZSTD_decompressSequences_bodySplitLitBuffer");
(void)frame;
/* Regen sequences */
if (nbSeq) {
seqState_t seqState;
dctx->fseEntropy = 1;
{ U32 i; for (i=0; i<ZSTD_REP_NUM; i++) seqState.prevOffset[i] = dctx->entropy.rep[i]; }
RETURN_ERROR_IF(
ERR_isError(BIT_initDStream(&seqState.DStream, ip, iend-ip)),
corruption_detected, "");
ZSTD_initFseState(&seqState.stateLL, &seqState.DStream, dctx->LLTptr);
ZSTD_initFseState(&seqState.stateOffb, &seqState.DStream, dctx->OFTptr);
ZSTD_initFseState(&seqState.stateML, &seqState.DStream, dctx->MLTptr);
assert(dst != NULL);
ZSTD_STATIC_ASSERT(
BIT_DStream_unfinished < BIT_DStream_completed &&
BIT_DStream_endOfBuffer < BIT_DStream_completed &&
BIT_DStream_completed < BIT_DStream_overflow);
/* decompress without overrunning litPtr begins */
{
seq_t sequence = ZSTD_decodeSequence(&seqState, isLongOffset);
/* Align the decompression loop to 32 + 16 bytes.
*
* zstd compiled with gcc-9 on an Intel i9-9900k shows 10% decompression
* speed swings based on the alignment of the decompression loop. This
* performance swing is caused by parts of the decompression loop falling
* out of the DSB. The entire decompression loop should fit in the DSB,
* when it can't we get much worse performance. You can measure if you've
* hit the good case or the bad case with this perf command for some
* compressed file test.zst:
*
* perf stat -e cycles -e instructions -e idq.all_dsb_cycles_any_uops \
* -e idq.all_mite_cycles_any_uops -- ./zstd -tq test.zst
*
* If you see most cycles served out of the MITE you've hit the bad case.
* If you see most cycles served out of the DSB you've hit the good case.
* If it is pretty even then you may be in an okay case.
*
* This issue has been reproduced on the following CPUs:
* - Kabylake: Macbook Pro (15-inch, 2019) 2.4 GHz Intel Core i9
* Use Instruments->Counters to get DSB/MITE cycles.
* I never got performance swings, but I was able to
* go from the good case of mostly DSB to half of the
* cycles served from MITE.
* - Coffeelake: Intel i9-9900k
* - Coffeelake: Intel i7-9700k
*
* I haven't been able to reproduce the instability or DSB misses on any
* of the following CPUS:
* - Haswell
* - Broadwell: Intel(R) Xeon(R) CPU E5-2680 v4 @ 2.40GH
* - Skylake
*
* Alignment is done for each of the three major decompression loops:
* - ZSTD_decompressSequences_bodySplitLitBuffer - presplit section of the literal buffer
* - ZSTD_decompressSequences_bodySplitLitBuffer - postsplit section of the literal buffer
* - ZSTD_decompressSequences_body
* Alignment choices are made to minimize large swings on bad cases and influence on performance
* from changes external to this code, rather than to overoptimize on the current commit.
*
* If you are seeing performance stability this script can help test.
* It tests on 4 commits in zstd where I saw performance change.
*
* https://gist.github.com/terrelln/9889fc06a423fd5ca6e99351564473f4
*/
#if defined(__GNUC__) && defined(__x86_64__)
__asm__(".p2align 6");
# if __GNUC__ >= 7
/* good for gcc-7, gcc-9, and gcc-11 */
__asm__("nop");
__asm__(".p2align 5");
__asm__("nop");
__asm__(".p2align 4");
# if __GNUC__ == 8 || __GNUC__ == 10
/* good for gcc-8 and gcc-10 */
__asm__("nop");
__asm__(".p2align 3");
# endif
# endif
#endif
/* Handle the initial state where litBuffer is currently split between dst and litExtraBuffer */
for (; litPtr + sequence.litLength <= dctx->litBufferEnd; ) {
size_t const oneSeqSize = ZSTD_execSequenceSplitLitBuffer(op, oend, litPtr + sequence.litLength - WILDCOPY_OVERLENGTH, sequence, &litPtr, litBufferEnd, prefixStart, vBase, dictEnd);
#if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE)
assert(!ZSTD_isError(oneSeqSize));
if (frame) ZSTD_assertValidSequence(dctx, op, oend, sequence, prefixStart, vBase);
#endif
if (UNLIKELY(ZSTD_isError(oneSeqSize)))
return oneSeqSize;
DEBUGLOG(6, "regenerated sequence size : %u", (U32)oneSeqSize);
op += oneSeqSize;
if (UNLIKELY(!--nbSeq))
break;
BIT_reloadDStream(&(seqState.DStream));
sequence = ZSTD_decodeSequence(&seqState, isLongOffset);
}
/* If there are more sequences, they will need to read literals from litExtraBuffer; copy over the remainder from dst and update litPtr and litEnd */
if (nbSeq > 0) {
const size_t leftoverLit = dctx->litBufferEnd - litPtr;
if (leftoverLit)
{
RETURN_ERROR_IF(leftoverLit > (size_t)(oend - op), dstSize_tooSmall, "remaining lit must fit within dstBuffer");
ZSTD_safecopyDstBeforeSrc(op, litPtr, leftoverLit);
sequence.litLength -= leftoverLit;
op += leftoverLit;
}
litPtr = dctx->litExtraBuffer;
litBufferEnd = dctx->litExtraBuffer + ZSTD_LITBUFFEREXTRASIZE;
dctx->litBufferLocation = ZSTD_not_in_dst;
{
size_t const oneSeqSize = ZSTD_execSequence(op, oend, sequence, &litPtr, litBufferEnd, prefixStart, vBase, dictEnd);
#if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE)
assert(!ZSTD_isError(oneSeqSize));
if (frame) ZSTD_assertValidSequence(dctx, op, oend, sequence, prefixStart, vBase);
#endif
if (UNLIKELY(ZSTD_isError(oneSeqSize)))
return oneSeqSize;
DEBUGLOG(6, "regenerated sequence size : %u", (U32)oneSeqSize);
op += oneSeqSize;
if (--nbSeq)
BIT_reloadDStream(&(seqState.DStream));
}
}
}
if (nbSeq > 0) /* there is remaining lit from extra buffer */
{
#if defined(__GNUC__) && defined(__x86_64__)
__asm__(".p2align 6");
__asm__("nop");
# if __GNUC__ != 7
/* worse for gcc-7 better for gcc-8, gcc-9, and gcc-10 and clang */
__asm__(".p2align 4");
__asm__("nop");
__asm__(".p2align 3");
# elif __GNUC__ >= 11
__asm__(".p2align 3");
# else
__asm__(".p2align 5");
__asm__("nop");
__asm__(".p2align 3");
# endif
#endif
for (; ; ) {
seq_t const sequence = ZSTD_decodeSequence(&seqState, isLongOffset);
size_t const oneSeqSize = ZSTD_execSequence(op, oend, sequence, &litPtr, litBufferEnd, prefixStart, vBase, dictEnd);
#if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE)
assert(!ZSTD_isError(oneSeqSize));
if (frame) ZSTD_assertValidSequence(dctx, op, oend, sequence, prefixStart, vBase);
#endif
if (UNLIKELY(ZSTD_isError(oneSeqSize)))
return oneSeqSize;
DEBUGLOG(6, "regenerated sequence size : %u", (U32)oneSeqSize);
op += oneSeqSize;
if (UNLIKELY(!--nbSeq))
break;
BIT_reloadDStream(&(seqState.DStream));
}
}
/* check if reached exact end */
DEBUGLOG(5, "ZSTD_decompressSequences_bodySplitLitBuffer: after decode loop, remaining nbSeq : %i", nbSeq);
RETURN_ERROR_IF(nbSeq, corruption_detected, "");
RETURN_ERROR_IF(BIT_reloadDStream(&seqState.DStream) < BIT_DStream_completed, corruption_detected, "");
/* save reps for next block */
{ U32 i; for (i=0; i<ZSTD_REP_NUM; i++) dctx->entropy.rep[i] = (U32)(seqState.prevOffset[i]); }
}
/* last literal segment */
if (dctx->litBufferLocation == ZSTD_split) /* split hasn't been reached yet, first get dst then copy litExtraBuffer */
{
size_t const lastLLSize = litBufferEnd - litPtr;
RETURN_ERROR_IF(lastLLSize > (size_t)(oend - op), dstSize_tooSmall, "");
if (op != NULL) {
ZSTD_memmove(op, litPtr, lastLLSize);
op += lastLLSize;
}
litPtr = dctx->litExtraBuffer;
litBufferEnd = dctx->litExtraBuffer + ZSTD_LITBUFFEREXTRASIZE;
dctx->litBufferLocation = ZSTD_not_in_dst;
}
{ size_t const lastLLSize = litBufferEnd - litPtr;
RETURN_ERROR_IF(lastLLSize > (size_t)(oend-op), dstSize_tooSmall, "");
if (op != NULL) {
ZSTD_memcpy(op, litPtr, lastLLSize);
op += lastLLSize;
}
}
return op-ostart;
}
FORCE_INLINE_TEMPLATE size_t
DONT_VECTORIZE
ZSTD_decompressSequences_body(ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
const BYTE* ip = (const BYTE*)seqStart;
const BYTE* const iend = ip + seqSize;
BYTE* const ostart = (BYTE*)dst;
BYTE* const oend = dctx->litBufferLocation == ZSTD_not_in_dst ? ostart + maxDstSize : dctx->litBuffer;
BYTE* op = ostart;
const BYTE* litPtr = dctx->litPtr;
const BYTE* const litEnd = litPtr + dctx->litSize;
const BYTE* const prefixStart = (const BYTE*)(dctx->prefixStart);
const BYTE* const vBase = (const BYTE*)(dctx->virtualStart);
const BYTE* const dictEnd = (const BYTE*)(dctx->dictEnd);
DEBUGLOG(5, "ZSTD_decompressSequences_body");
(void)frame;
/* Regen sequences */
if (nbSeq) {
seqState_t seqState;
dctx->fseEntropy = 1;
{ U32 i; for (i = 0; i < ZSTD_REP_NUM; i++) seqState.prevOffset[i] = dctx->entropy.rep[i]; }
RETURN_ERROR_IF(
ERR_isError(BIT_initDStream(&seqState.DStream, ip, iend - ip)),
corruption_detected, "");
ZSTD_initFseState(&seqState.stateLL, &seqState.DStream, dctx->LLTptr);
ZSTD_initFseState(&seqState.stateOffb, &seqState.DStream, dctx->OFTptr);
ZSTD_initFseState(&seqState.stateML, &seqState.DStream, dctx->MLTptr);
assert(dst != NULL);
ZSTD_STATIC_ASSERT(
BIT_DStream_unfinished < BIT_DStream_completed &&
BIT_DStream_endOfBuffer < BIT_DStream_completed &&
BIT_DStream_completed < BIT_DStream_overflow);
#if defined(__GNUC__) && defined(__x86_64__)
__asm__(".p2align 6");
__asm__("nop");
# if __GNUC__ >= 7
__asm__(".p2align 5");
__asm__("nop");
__asm__(".p2align 3");
# else
__asm__(".p2align 4");
__asm__("nop");
__asm__(".p2align 3");
# endif
#endif
for ( ; ; ) {
seq_t const sequence = ZSTD_decodeSequence(&seqState, isLongOffset);
size_t const oneSeqSize = ZSTD_execSequence(op, oend, sequence, &litPtr, litEnd, prefixStart, vBase, dictEnd);
#if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE)
assert(!ZSTD_isError(oneSeqSize));
if (frame) ZSTD_assertValidSequence(dctx, op, oend, sequence, prefixStart, vBase);
#endif
if (UNLIKELY(ZSTD_isError(oneSeqSize)))
return oneSeqSize;
DEBUGLOG(6, "regenerated sequence size : %u", (U32)oneSeqSize);
op += oneSeqSize;
if (UNLIKELY(!--nbSeq))
break;
BIT_reloadDStream(&(seqState.DStream));
}
/* check if reached exact end */
DEBUGLOG(5, "ZSTD_decompressSequences_body: after decode loop, remaining nbSeq : %i", nbSeq);
RETURN_ERROR_IF(nbSeq, corruption_detected, "");
RETURN_ERROR_IF(BIT_reloadDStream(&seqState.DStream) < BIT_DStream_completed, corruption_detected, "");
/* save reps for next block */
{ U32 i; for (i=0; i<ZSTD_REP_NUM; i++) dctx->entropy.rep[i] = (U32)(seqState.prevOffset[i]); }
}
/* last literal segment */
{ size_t const lastLLSize = litEnd - litPtr;
RETURN_ERROR_IF(lastLLSize > (size_t)(oend-op), dstSize_tooSmall, "");
if (op != NULL) {
ZSTD_memcpy(op, litPtr, lastLLSize);
op += lastLLSize;
}
}
return op-ostart;
}
static size_t
ZSTD_decompressSequences_default(ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
return ZSTD_decompressSequences_body(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
static size_t
ZSTD_decompressSequencesSplitLitBuffer_default(ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
return ZSTD_decompressSequences_bodySplitLitBuffer(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
#endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG */
#ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT
FORCE_INLINE_TEMPLATE size_t
ZSTD_prefetchMatch(size_t prefetchPos, seq_t const sequence,
const BYTE* const prefixStart, const BYTE* const dictEnd)
{
prefetchPos += sequence.litLength;
{ const BYTE* const matchBase = (sequence.offset > prefetchPos) ? dictEnd : prefixStart;
const BYTE* const match = matchBase + prefetchPos - sequence.offset; /* note : this operation can overflow when seq.offset is really too large, which can only happen when input is corrupted.
* No consequence though : memory address is only used for prefetching, not for dereferencing */
PREFETCH_L1(match); PREFETCH_L1(match+CACHELINE_SIZE); /* note : it's safe to invoke PREFETCH() on any memory address, including invalid ones */
}
return prefetchPos + sequence.matchLength;
}
/* This decoding function employs prefetching
* to reduce latency impact of cache misses.
* It's generally employed when block contains a significant portion of long-distance matches
* or when coupled with a "cold" dictionary */
FORCE_INLINE_TEMPLATE size_t
ZSTD_decompressSequencesLong_body(
ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
const BYTE* ip = (const BYTE*)seqStart;
const BYTE* const iend = ip + seqSize;
BYTE* const ostart = (BYTE*)dst;
BYTE* const oend = dctx->litBufferLocation == ZSTD_in_dst ? dctx->litBuffer : ostart + maxDstSize;
BYTE* op = ostart;
const BYTE* litPtr = dctx->litPtr;
const BYTE* litBufferEnd = dctx->litBufferEnd;
const BYTE* const prefixStart = (const BYTE*) (dctx->prefixStart);
const BYTE* const dictStart = (const BYTE*) (dctx->virtualStart);
const BYTE* const dictEnd = (const BYTE*) (dctx->dictEnd);
(void)frame;
/* Regen sequences */
if (nbSeq) {
#define STORED_SEQS 8
#define STORED_SEQS_MASK (STORED_SEQS-1)
#define ADVANCED_SEQS STORED_SEQS
seq_t sequences[STORED_SEQS];
int const seqAdvance = MIN(nbSeq, ADVANCED_SEQS);
seqState_t seqState;
int seqNb;
size_t prefetchPos = (size_t)(op-prefixStart); /* track position relative to prefixStart */
dctx->fseEntropy = 1;
{ int i; for (i=0; i<ZSTD_REP_NUM; i++) seqState.prevOffset[i] = dctx->entropy.rep[i]; }
assert(dst != NULL);
assert(iend >= ip);
RETURN_ERROR_IF(
ERR_isError(BIT_initDStream(&seqState.DStream, ip, iend-ip)),
corruption_detected, "");
ZSTD_initFseState(&seqState.stateLL, &seqState.DStream, dctx->LLTptr);
ZSTD_initFseState(&seqState.stateOffb, &seqState.DStream, dctx->OFTptr);
ZSTD_initFseState(&seqState.stateML, &seqState.DStream, dctx->MLTptr);
/* prepare in advance */
for (seqNb=0; (BIT_reloadDStream(&seqState.DStream) <= BIT_DStream_completed) && (seqNb<seqAdvance); seqNb++) {
seq_t const sequence = ZSTD_decodeSequence(&seqState, isLongOffset);
prefetchPos = ZSTD_prefetchMatch(prefetchPos, sequence, prefixStart, dictEnd);
sequences[seqNb] = sequence;
}
RETURN_ERROR_IF(seqNb<seqAdvance, corruption_detected, "");
/* decompress without stomping litBuffer */
for (; (BIT_reloadDStream(&(seqState.DStream)) <= BIT_DStream_completed) && (seqNb < nbSeq); seqNb++) {
seq_t sequence = ZSTD_decodeSequence(&seqState, isLongOffset);
size_t oneSeqSize;
if (dctx->litBufferLocation == ZSTD_split && litPtr + sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK].litLength > dctx->litBufferEnd)
{
/* lit buffer is reaching split point, empty out the first buffer and transition to litExtraBuffer */
const size_t leftoverLit = dctx->litBufferEnd - litPtr;
if (leftoverLit)
{
RETURN_ERROR_IF(leftoverLit > (size_t)(oend - op), dstSize_tooSmall, "remaining lit must fit within dstBuffer");
ZSTD_safecopyDstBeforeSrc(op, litPtr, leftoverLit);
sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK].litLength -= leftoverLit;
op += leftoverLit;
}
litPtr = dctx->litExtraBuffer;
litBufferEnd = dctx->litExtraBuffer + ZSTD_LITBUFFEREXTRASIZE;
dctx->litBufferLocation = ZSTD_not_in_dst;
oneSeqSize = ZSTD_execSequence(op, oend, sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK], &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd);
#if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE)
assert(!ZSTD_isError(oneSeqSize));
if (frame) ZSTD_assertValidSequence(dctx, op, oend, sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK], prefixStart, dictStart);
#endif
if (ZSTD_isError(oneSeqSize)) return oneSeqSize;
prefetchPos = ZSTD_prefetchMatch(prefetchPos, sequence, prefixStart, dictEnd);
sequences[seqNb & STORED_SEQS_MASK] = sequence;
op += oneSeqSize;
}
else
{
/* lit buffer is either wholly contained in first or second split, or not split at all*/
oneSeqSize = dctx->litBufferLocation == ZSTD_split ?
ZSTD_execSequenceSplitLitBuffer(op, oend, litPtr + sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK].litLength - WILDCOPY_OVERLENGTH, sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK], &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd) :
ZSTD_execSequence(op, oend, sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK], &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd);
#if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE)
assert(!ZSTD_isError(oneSeqSize));
if (frame) ZSTD_assertValidSequence(dctx, op, oend, sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK], prefixStart, dictStart);
#endif
if (ZSTD_isError(oneSeqSize)) return oneSeqSize;
prefetchPos = ZSTD_prefetchMatch(prefetchPos, sequence, prefixStart, dictEnd);
sequences[seqNb & STORED_SEQS_MASK] = sequence;
op += oneSeqSize;
}
}
RETURN_ERROR_IF(seqNb<nbSeq, corruption_detected, "");
/* finish queue */
seqNb -= seqAdvance;
for ( ; seqNb<nbSeq ; seqNb++) {
seq_t *sequence = &(sequences[seqNb&STORED_SEQS_MASK]);
if (dctx->litBufferLocation == ZSTD_split && litPtr + sequence->litLength > dctx->litBufferEnd)
{
const size_t leftoverLit = dctx->litBufferEnd - litPtr;
if (leftoverLit)
{
RETURN_ERROR_IF(leftoverLit > (size_t)(oend - op), dstSize_tooSmall, "remaining lit must fit within dstBuffer");
ZSTD_safecopyDstBeforeSrc(op, litPtr, leftoverLit);
sequence->litLength -= leftoverLit;
op += leftoverLit;
}
litPtr = dctx->litExtraBuffer;
litBufferEnd = dctx->litExtraBuffer + ZSTD_LITBUFFEREXTRASIZE;
dctx->litBufferLocation = ZSTD_not_in_dst;
{
size_t const oneSeqSize = ZSTD_execSequence(op, oend, *sequence, &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd);
#if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE)
assert(!ZSTD_isError(oneSeqSize));
if (frame) ZSTD_assertValidSequence(dctx, op, oend, sequences[seqNb&STORED_SEQS_MASK], prefixStart, dictStart);
#endif
if (ZSTD_isError(oneSeqSize)) return oneSeqSize;
op += oneSeqSize;
}
}
else
{
size_t const oneSeqSize = dctx->litBufferLocation == ZSTD_split ?
ZSTD_execSequenceSplitLitBuffer(op, oend, litPtr + sequence->litLength - WILDCOPY_OVERLENGTH, *sequence, &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd) :
ZSTD_execSequence(op, oend, *sequence, &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd);
#if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE)
assert(!ZSTD_isError(oneSeqSize));
if (frame) ZSTD_assertValidSequence(dctx, op, oend, sequences[seqNb&STORED_SEQS_MASK], prefixStart, dictStart);
#endif
if (ZSTD_isError(oneSeqSize)) return oneSeqSize;
op += oneSeqSize;
}
}
/* save reps for next block */
{ U32 i; for (i=0; i<ZSTD_REP_NUM; i++) dctx->entropy.rep[i] = (U32)(seqState.prevOffset[i]); }
}
/* last literal segment */
if (dctx->litBufferLocation == ZSTD_split) /* first deplete literal buffer in dst, then copy litExtraBuffer */
{
size_t const lastLLSize = litBufferEnd - litPtr;
RETURN_ERROR_IF(lastLLSize > (size_t)(oend - op), dstSize_tooSmall, "");
if (op != NULL) {
ZSTD_memmove(op, litPtr, lastLLSize);
op += lastLLSize;
}
litPtr = dctx->litExtraBuffer;
litBufferEnd = dctx->litExtraBuffer + ZSTD_LITBUFFEREXTRASIZE;
}
{ size_t const lastLLSize = litBufferEnd - litPtr;
RETURN_ERROR_IF(lastLLSize > (size_t)(oend-op), dstSize_tooSmall, "");
if (op != NULL) {
ZSTD_memmove(op, litPtr, lastLLSize);
op += lastLLSize;
}
}
return op-ostart;
}
static size_t
ZSTD_decompressSequencesLong_default(ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
return ZSTD_decompressSequencesLong_body(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
#endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT */
#if DYNAMIC_BMI2
#ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG
static BMI2_TARGET_ATTRIBUTE size_t
DONT_VECTORIZE
ZSTD_decompressSequences_bmi2(ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
return ZSTD_decompressSequences_body(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
static BMI2_TARGET_ATTRIBUTE size_t
DONT_VECTORIZE
ZSTD_decompressSequencesSplitLitBuffer_bmi2(ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
return ZSTD_decompressSequences_bodySplitLitBuffer(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
#endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG */
#ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT
static BMI2_TARGET_ATTRIBUTE size_t
ZSTD_decompressSequencesLong_bmi2(ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
return ZSTD_decompressSequencesLong_body(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
#endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT */
#endif /* DYNAMIC_BMI2 */
typedef size_t (*ZSTD_decompressSequences_t)(
ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame);
#ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG
static size_t
ZSTD_decompressSequences(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
DEBUGLOG(5, "ZSTD_decompressSequences");
#if DYNAMIC_BMI2
if (ZSTD_DCtx_get_bmi2(dctx)) {
return ZSTD_decompressSequences_bmi2(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
#endif
return ZSTD_decompressSequences_default(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
static size_t
ZSTD_decompressSequencesSplitLitBuffer(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
DEBUGLOG(5, "ZSTD_decompressSequencesSplitLitBuffer");
#if DYNAMIC_BMI2
if (ZSTD_DCtx_get_bmi2(dctx)) {
return ZSTD_decompressSequencesSplitLitBuffer_bmi2(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
#endif
return ZSTD_decompressSequencesSplitLitBuffer_default(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
#endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG */
#ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT
/* ZSTD_decompressSequencesLong() :
* decompression function triggered when a minimum share of offsets is considered "long",
* aka out of cache.
* note : "long" definition seems overloaded here, sometimes meaning "wider than bitstream register", and sometimes meaning "farther than memory cache distance".
* This function will try to mitigate main memory latency through the use of prefetching */
static size_t
ZSTD_decompressSequencesLong(ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset,
const int frame)
{
DEBUGLOG(5, "ZSTD_decompressSequencesLong");
#if DYNAMIC_BMI2
if (ZSTD_DCtx_get_bmi2(dctx)) {
return ZSTD_decompressSequencesLong_bmi2(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
#endif
return ZSTD_decompressSequencesLong_default(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
}
#endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT */
#if !defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \
!defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG)
/* ZSTD_getLongOffsetsShare() :
* condition : offTable must be valid
* @return : "share" of long offsets (arbitrarily defined as > (1<<23))
* compared to maximum possible of (1<<OffFSELog) */
static unsigned
ZSTD_getLongOffsetsShare(const ZSTD_seqSymbol* offTable)
{
const void* ptr = offTable;
U32 const tableLog = ((const ZSTD_seqSymbol_header*)ptr)[0].tableLog;
const ZSTD_seqSymbol* table = offTable + 1;
U32 const max = 1 << tableLog;
U32 u, total = 0;
DEBUGLOG(5, "ZSTD_getLongOffsetsShare: (tableLog=%u)", tableLog);
assert(max <= (1 << OffFSELog)); /* max not too large */
for (u=0; u<max; u++) {
if (table[u].nbAdditionalBits > 22) total += 1;
}
assert(tableLog <= OffFSELog);
total <<= (OffFSELog - tableLog); /* scale to OffFSELog */
return total;
}
#endif
size_t
ZSTD_decompressBlock_internal(ZSTD_DCtx* dctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize, const int frame, const streaming_operation streaming)
{ /* blockType == blockCompressed */
const BYTE* ip = (const BYTE*)src;
/* isLongOffset must be true if there are long offsets.
* Offsets are long if they are larger than 2^STREAM_ACCUMULATOR_MIN.
* We don't expect that to be the case in 64-bit mode.
* In block mode, window size is not known, so we have to be conservative.
* (note: but it could be evaluated from current-lowLimit)
*/
ZSTD_longOffset_e const isLongOffset = (ZSTD_longOffset_e)(MEM_32bits() && (!frame || (dctx->fParams.windowSize > (1ULL << STREAM_ACCUMULATOR_MIN))));
DEBUGLOG(5, "ZSTD_decompressBlock_internal (size : %u)", (U32)srcSize);
RETURN_ERROR_IF(srcSize >= ZSTD_BLOCKSIZE_MAX, srcSize_wrong, "");
/* Decode literals section */
{ size_t const litCSize = ZSTD_decodeLiteralsBlock(dctx, src, srcSize, dst, dstCapacity, streaming);
DEBUGLOG(5, "ZSTD_decodeLiteralsBlock : %u", (U32)litCSize);
if (ZSTD_isError(litCSize)) return litCSize;
ip += litCSize;
srcSize -= litCSize;
}
/* Build Decoding Tables */
{
/* These macros control at build-time which decompressor implementation
* we use. If neither is defined, we do some inspection and dispatch at
* runtime.
*/
#if !defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \
!defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG)
int usePrefetchDecoder = dctx->ddictIsCold;
#endif
int nbSeq;
size_t const seqHSize = ZSTD_decodeSeqHeaders(dctx, &nbSeq, ip, srcSize);
if (ZSTD_isError(seqHSize)) return seqHSize;
ip += seqHSize;
srcSize -= seqHSize;
RETURN_ERROR_IF(dst == NULL && nbSeq > 0, dstSize_tooSmall, "NULL not handled");
#if !defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \
!defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG)
if ( !usePrefetchDecoder
&& (!frame || (dctx->fParams.windowSize > (1<<24)))
&& (nbSeq>ADVANCED_SEQS) ) { /* could probably use a larger nbSeq limit */
U32 const shareLongOffsets = ZSTD_getLongOffsetsShare(dctx->OFTptr);
U32 const minShare = MEM_64bits() ? 7 : 20; /* heuristic values, correspond to 2.73% and 7.81% */
usePrefetchDecoder = (shareLongOffsets >= minShare);
}
#endif
dctx->ddictIsCold = 0;
#if !defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \
!defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG)
if (usePrefetchDecoder)
#endif
#ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT
return ZSTD_decompressSequencesLong(dctx, dst, dstCapacity, ip, srcSize, nbSeq, isLongOffset, frame);
#endif
#ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG
/* else */
if (dctx->litBufferLocation == ZSTD_split)
return ZSTD_decompressSequencesSplitLitBuffer(dctx, dst, dstCapacity, ip, srcSize, nbSeq, isLongOffset, frame);
else
return ZSTD_decompressSequences(dctx, dst, dstCapacity, ip, srcSize, nbSeq, isLongOffset, frame);
#endif
}
}
void ZSTD_checkContinuity(ZSTD_DCtx* dctx, const void* dst, size_t dstSize)
{
if (dst != dctx->previousDstEnd && dstSize > 0) { /* not contiguous */
dctx->dictEnd = dctx->previousDstEnd;
dctx->virtualStart = (const char*)dst - ((const char*)(dctx->previousDstEnd) - (const char*)(dctx->prefixStart));
dctx->prefixStart = dst;
dctx->previousDstEnd = dst;
}
}
size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize)
{
size_t dSize;
ZSTD_checkContinuity(dctx, dst, dstCapacity);
dSize = ZSTD_decompressBlock_internal(dctx, dst, dstCapacity, src, srcSize, /* frame */ 0, not_streaming);
dctx->previousDstEnd = (char*)dst + dSize;
return dSize;
}
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