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Update zstd to 1.5.4.

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This commit is contained in:
Bartosz Taudul
2023-02-10 20:25:40 +01:00
parent 69d0510255
commit 0d6fb703b4
66 changed files with 4541 additions and 3026 deletions
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zstd/decompress/zstd_decompress_block.c
+186 -65
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@@ -1,5 +1,5 @@
/*
* Copyright (c) Yann Collet, Facebook, Inc.
* Copyright (c) Meta Platforms, Inc. and affiliates.
* All rights reserved.
*
* This source code is licensed under both the BSD-style license (found in the
@@ -20,12 +20,12 @@
#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"
#include "../common/bits.h" /* ZSTD_highbit32 */
/*_*******************************************************
* Macros
@@ -89,7 +89,7 @@ static void ZSTD_allocateLiteralsBuffer(ZSTD_DCtx* dctx, void* const dst, const
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 */
/* initially this will be stored entirely in dst during huffman decoding, it will partially be shifted to litExtraBuffer after */
dctx->litBuffer = (BYTE*)dst + expectedWriteSize - litSize;
dctx->litBufferEnd = (BYTE*)dst + expectedWriteSize;
}
@@ -134,13 +134,16 @@ size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
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");
RETURN_ERROR_IF(srcSize < 5, corruption_detected, "srcSize >= MIN_CBLOCK_SIZE == 2; 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);
int const flags = 0
| (ZSTD_DCtx_get_bmi2(dctx) ? HUF_flags_bmi2 : 0)
| (dctx->disableHufAsm ? HUF_flags_disableAsm : 0);
switch(lhlCode)
{
case 0: case 1: default: /* note : default is impossible, since lhlCode into [0..3] */
@@ -165,6 +168,10 @@ size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
}
RETURN_ERROR_IF(litSize > 0 && dst == NULL, dstSize_tooSmall, "NULL not handled");
RETURN_ERROR_IF(litSize > ZSTD_BLOCKSIZE_MAX, corruption_detected, "");
if (!singleStream)
RETURN_ERROR_IF(litSize < MIN_LITERALS_FOR_4_STREAMS, literals_headerWrong,
"Not enough literals (%zu) for the 4-streams mode (min %u)",
litSize, MIN_LITERALS_FOR_4_STREAMS);
RETURN_ERROR_IF(litCSize + lhSize > srcSize, corruption_detected, "");
RETURN_ERROR_IF(expectedWriteSize < litSize , dstSize_tooSmall, "");
ZSTD_allocateLiteralsBuffer(dctx, dst, dstCapacity, litSize, streaming, expectedWriteSize, 0);
@@ -176,13 +183,14 @@ size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
if (litEncType==set_repeat) {
if (singleStream) {
hufSuccess = HUF_decompress1X_usingDTable_bmi2(
hufSuccess = HUF_decompress1X_usingDTable(
dctx->litBuffer, litSize, istart+lhSize, litCSize,
dctx->HUFptr, ZSTD_DCtx_get_bmi2(dctx));
dctx->HUFptr, flags);
} else {
hufSuccess = HUF_decompress4X_usingDTable_bmi2(
assert(litSize >= MIN_LITERALS_FOR_4_STREAMS);
hufSuccess = HUF_decompress4X_usingDTable(
dctx->litBuffer, litSize, istart+lhSize, litCSize,
dctx->HUFptr, ZSTD_DCtx_get_bmi2(dctx));
dctx->HUFptr, flags);
}
} else {
if (singleStream) {
@@ -190,18 +198,18 @@ size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
hufSuccess = HUF_decompress1X_DCtx_wksp(
dctx->entropy.hufTable, dctx->litBuffer, litSize,
istart+lhSize, litCSize, dctx->workspace,
sizeof(dctx->workspace));
sizeof(dctx->workspace), flags);
#else
hufSuccess = HUF_decompress1X1_DCtx_wksp_bmi2(
hufSuccess = HUF_decompress1X1_DCtx_wksp(
dctx->entropy.hufTable, dctx->litBuffer, litSize,
istart+lhSize, litCSize, dctx->workspace,
sizeof(dctx->workspace), ZSTD_DCtx_get_bmi2(dctx));
sizeof(dctx->workspace), flags);
#endif
} else {
hufSuccess = HUF_decompress4X_hufOnly_wksp_bmi2(
hufSuccess = HUF_decompress4X_hufOnly_wksp(
dctx->entropy.hufTable, dctx->litBuffer, litSize,
istart+lhSize, litCSize, dctx->workspace,
sizeof(dctx->workspace), ZSTD_DCtx_get_bmi2(dctx));
sizeof(dctx->workspace), flags);
}
}
if (dctx->litBufferLocation == ZSTD_split)
@@ -237,6 +245,7 @@ size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
break;
case 3:
lhSize = 3;
RETURN_ERROR_IF(srcSize<3, corruption_detected, "srcSize >= MIN_CBLOCK_SIZE == 2; here we need lhSize = 3");
litSize = MEM_readLE24(istart) >> 4;
break;
}
@@ -279,12 +288,13 @@ size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
break;
case 1:
lhSize = 2;
RETURN_ERROR_IF(srcSize<3, corruption_detected, "srcSize >= MIN_CBLOCK_SIZE == 2; here we need lhSize+1 = 3");
litSize = MEM_readLE16(istart) >> 4;
break;
case 3:
lhSize = 3;
RETURN_ERROR_IF(srcSize<4, corruption_detected, "srcSize >= MIN_CBLOCK_SIZE == 2; here we need lhSize+1 = 4");
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");
@@ -506,14 +516,15 @@ void ZSTD_buildFSETable_body(ZSTD_seqSymbol* dt,
for (i = 8; i < n; i += 8) {
MEM_write64(spread + pos + i, sv);
}
pos += n;
assert(n>=0);
pos += (size_t)n;
}
}
/* Now we spread those positions across the table.
* The benefit of doing it in two stages is that we avoid the the
* The benefit of doing it in two stages is that we avoid 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.
* We unroll the loop twice, since that is what empirically worked best.
*/
{
size_t position = 0;
@@ -540,7 +551,7 @@ void ZSTD_buildFSETable_body(ZSTD_seqSymbol* dt,
for (i=0; i<n; i++) {
tableDecode[position].baseValue = s;
position = (position + step) & tableMask;
while (position > highThreshold) position = (position + step) & tableMask; /* lowprob area */
while (UNLIKELY(position > highThreshold)) position = (position + step) & tableMask; /* lowprob area */
} }
assert(position == 0); /* position must reach all cells once, otherwise normalizedCounter is incorrect */
}
@@ -551,7 +562,7 @@ void ZSTD_buildFSETable_body(ZSTD_seqSymbol* dt,
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].nbBits = (BYTE) (tableLog - ZSTD_highbit32(nextState) );
tableDecode[u].nextState = (U16) ( (nextState << tableDecode[u].nbBits) - tableSize);
assert(nbAdditionalBits[symbol] < 255);
tableDecode[u].nbAdditionalBits = nbAdditionalBits[symbol];
@@ -964,6 +975,11 @@ size_t ZSTD_execSequence(BYTE* op,
assert(op != NULL /* Precondition */);
assert(oend_w < oend /* No underflow */);
#if defined(__aarch64__)
/* prefetch sequence starting from match that will be used for copy later */
PREFETCH_L1(match);
#endif
/* Handle edge cases in a slow path:
* - Read beyond end of literals
* - Match end is within WILDCOPY_OVERLIMIT of oend
@@ -1154,7 +1170,7 @@ ZSTD_updateFseStateWithDInfo(ZSTD_fseState* DStatePtr, BIT_DStream_t* bitD, U16
}
/* 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)
* offset bits. But we can only read at most STREAM_ACCUMULATOR_MIN_32
* bits before reloading. This value is the maximum number of bytes we read
* after reloading when we are decoding long offsets.
*/
@@ -1169,9 +1185,27 @@ FORCE_INLINE_TEMPLATE seq_t
ZSTD_decodeSequence(seqState_t* seqState, const ZSTD_longOffset_e longOffsets)
{
seq_t seq;
/*
* ZSTD_seqSymbol is a structure with a total of 64 bits wide. So it can be
* loaded in one operation and extracted its fields by simply shifting or
* bit-extracting on aarch64.
* GCC doesn't recognize this and generates more unnecessary ldr/ldrb/ldrh
* operations that cause performance drop. This can be avoided by using this
* ZSTD_memcpy hack.
*/
#if defined(__aarch64__) && (defined(__GNUC__) && !defined(__clang__))
ZSTD_seqSymbol llDInfoS, mlDInfoS, ofDInfoS;
ZSTD_seqSymbol* const llDInfo = &llDInfoS;
ZSTD_seqSymbol* const mlDInfo = &mlDInfoS;
ZSTD_seqSymbol* const ofDInfo = &ofDInfoS;
ZSTD_memcpy(llDInfo, seqState->stateLL.table + seqState->stateLL.state, sizeof(ZSTD_seqSymbol));
ZSTD_memcpy(mlDInfo, seqState->stateML.table + seqState->stateML.state, sizeof(ZSTD_seqSymbol));
ZSTD_memcpy(ofDInfo, seqState->stateOffb.table + seqState->stateOffb.state, sizeof(ZSTD_seqSymbol));
#else
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;
#endif
seq.matchLength = mlDInfo->baseValue;
seq.litLength = llDInfo->baseValue;
{ U32 const ofBase = ofDInfo->baseValue;
@@ -1186,9 +1220,13 @@ ZSTD_decodeSequence(seqState_t* seqState, const ZSTD_longOffset_e longOffsets)
U32 const llnbBits = llDInfo->nbBits;
U32 const mlnbBits = mlDInfo->nbBits;
U32 const ofnbBits = ofDInfo->nbBits;
assert(llBits <= MaxLLBits);
assert(mlBits <= MaxMLBits);
assert(ofBits <= MaxOff);
/*
* As gcc has better branch and block analyzers, sometimes it is only
* valuable to mark likelyness for clang, it gives around 3-4% of
* valuable to mark likeliness for clang, it gives around 3-4% of
* performance.
*/
@@ -1201,13 +1239,16 @@ ZSTD_decodeSequence(seqState_t* seqState, const ZSTD_longOffset_e longOffsets)
#endif
ZSTD_STATIC_ASSERT(ZSTD_lo_isLongOffset == 1);
ZSTD_STATIC_ASSERT(LONG_OFFSETS_MAX_EXTRA_BITS_32 == 5);
assert(ofBits <= MaxOff);
ZSTD_STATIC_ASSERT(STREAM_ACCUMULATOR_MIN_32 > LONG_OFFSETS_MAX_EXTRA_BITS_32);
ZSTD_STATIC_ASSERT(STREAM_ACCUMULATOR_MIN_32 - LONG_OFFSETS_MAX_EXTRA_BITS_32 >= MaxMLBits);
if (MEM_32bits() && longOffsets && (ofBits >= STREAM_ACCUMULATOR_MIN_32)) {
U32 const extraBits = ofBits - MIN(ofBits, 32 - seqState->DStream.bitsConsumed);
/* Always read extra bits, this keeps the logic simple,
* avoids branches, and avoids accidentally reading 0 bits.
*/
U32 const extraBits = LONG_OFFSETS_MAX_EXTRA_BITS_32;
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 */
offset += BIT_readBitsFast(&seqState->DStream, extraBits);
} else {
offset = ofBase + BIT_readBitsFast(&seqState->DStream, ofBits/*>0*/); /* <= (ZSTD_WINDOWLOG_MAX-1) bits */
if (MEM_32bits()) BIT_reloadDStream(&seqState->DStream);
@@ -1552,7 +1593,7 @@ ZSTD_decompressSequences_body(ZSTD_DCtx* dctx,
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");
DEBUGLOG(5, "ZSTD_decompressSequences_body: nbSeq = %d", nbSeq);
(void)frame;
/* Regen sequences */
@@ -1945,34 +1986,79 @@ ZSTD_decompressSequencesLong(ZSTD_DCtx* dctx,
#endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT */
/**
* @returns The total size of the history referencable by zstd, including
* both the prefix and the extDict. At @p op any offset larger than this
* is invalid.
*/
static size_t ZSTD_totalHistorySize(BYTE* op, BYTE const* virtualStart)
{
return (size_t)(op - virtualStart);
}
#if !defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \
!defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG)
/* ZSTD_getLongOffsetsShare() :
typedef struct {
unsigned longOffsetShare;
unsigned maxNbAdditionalBits;
} ZSTD_OffsetInfo;
/* ZSTD_getOffsetInfo() :
* 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)
* compared to maximum possible of (1<<OffFSELog),
* as well as the maximum number additional bits required.
*/
static ZSTD_OffsetInfo
ZSTD_getOffsetInfo(const ZSTD_seqSymbol* offTable, int nbSeq)
{
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);
ZSTD_OffsetInfo info = {0, 0};
/* If nbSeq == 0, then the offTable is uninitialized, but we have
* no sequences, so both values should be 0.
*/
if (nbSeq != 0) {
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;
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(max <= (1 << OffFSELog)); /* max not too large */
for (u=0; u<max; u++) {
info.maxNbAdditionalBits = MAX(info.maxNbAdditionalBits, table[u].nbAdditionalBits);
if (table[u].nbAdditionalBits > 22) info.longOffsetShare += 1;
}
assert(tableLog <= OffFSELog);
info.longOffsetShare <<= (OffFSELog - tableLog); /* scale to OffFSELog */
}
assert(tableLog <= OffFSELog);
total <<= (OffFSELog - tableLog); /* scale to OffFSELog */
return total;
return info;
}
/**
* @returns The maximum offset we can decode in one read of our bitstream, without
* reloading more bits in the middle of the offset bits read. Any offsets larger
* than this must use the long offset decoder.
*/
static size_t ZSTD_maxShortOffset(void)
{
if (MEM_64bits()) {
/* We can decode any offset without reloading bits.
* This might change if the max window size grows.
*/
ZSTD_STATIC_ASSERT(ZSTD_WINDOWLOG_MAX <= 31);
return (size_t)-1;
} else {
/* The maximum offBase is (1 << (STREAM_ACCUMULATOR_MIN + 1)) - 1.
* This offBase would require STREAM_ACCUMULATOR_MIN extra bits.
* Then we have to subtract ZSTD_REP_NUM to get the maximum possible offset.
*/
size_t const maxOffbase = ((size_t)1 << (STREAM_ACCUMULATOR_MIN + 1)) - 1;
size_t const maxOffset = maxOffbase - ZSTD_REP_NUM;
assert(ZSTD_highbit32((U32)maxOffbase) == STREAM_ACCUMULATOR_MIN);
return maxOffset;
}
}
#endif
size_t
ZSTD_decompressBlock_internal(ZSTD_DCtx* dctx,
@@ -1980,20 +2066,21 @@ ZSTD_decompressBlock_internal(ZSTD_DCtx* dctx,
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, "");
/* Note : the wording of the specification
* allows compressed block to be sized exactly ZSTD_BLOCKSIZE_MAX.
* This generally does not happen, as it makes little sense,
* since an uncompressed block would feature same size and have no decompression cost.
* Also, note that decoder from reference libzstd before < v1.5.4
* would consider this edge case as an error.
* As a consequence, avoid generating compressed blocks of size ZSTD_BLOCKSIZE_MAX
* for broader compatibility with the deployed ecosystem of zstd decoders */
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);
DEBUGLOG(5, "ZSTD_decodeLiteralsBlock : cSize=%u, nbLiterals=%zu", (U32)litCSize, dctx->litSize);
if (ZSTD_isError(litCSize)) return litCSize;
ip += litCSize;
srcSize -= litCSize;
@@ -2001,6 +2088,23 @@ ZSTD_decompressBlock_internal(ZSTD_DCtx* dctx,
/* Build Decoding Tables */
{
/* Compute the maximum block size, which must also work when !frame and fParams are unset.
* Additionally, take the min with dstCapacity to ensure that the totalHistorySize fits in a size_t.
*/
size_t const blockSizeMax = MIN(dstCapacity, (frame ? dctx->fParams.blockSizeMax : ZSTD_BLOCKSIZE_MAX));
size_t const totalHistorySize = ZSTD_totalHistorySize((BYTE*)dst + blockSizeMax, (BYTE const*)dctx->virtualStart);
/* isLongOffset must be true if there are long offsets.
* Offsets are long if they are larger than ZSTD_maxShortOffset().
* We don't expect that to be the case in 64-bit mode.
*
* We check here to see if our history is large enough to allow long offsets.
* If it isn't, then we can't possible have (valid) long offsets. If the offset
* is invalid, then it is okay to read it incorrectly.
*
* If isLongOffsets is true, then we will later check our decoding table to see
* if it is even possible to generate long offsets.
*/
ZSTD_longOffset_e isLongOffset = (ZSTD_longOffset_e)(MEM_32bits() && (totalHistorySize > ZSTD_maxShortOffset()));
/* These macros control at build-time which decompressor implementation
* we use. If neither is defined, we do some inspection and dispatch at
* runtime.
@@ -2008,6 +2112,11 @@ ZSTD_decompressBlock_internal(ZSTD_DCtx* dctx,
#if !defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \
!defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG)
int usePrefetchDecoder = dctx->ddictIsCold;
#else
/* Set to 1 to avoid computing offset info if we don't need to.
* Otherwise this value is ignored.
*/
int usePrefetchDecoder = 1;
#endif
int nbSeq;
size_t const seqHSize = ZSTD_decodeSeqHeaders(dctx, &nbSeq, ip, srcSize);
@@ -2017,26 +2126,38 @@ ZSTD_decompressBlock_internal(ZSTD_DCtx* dctx,
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);
/* If we could potentially have long offsets, or we might want to use the prefetch decoder,
* compute information about the share of long offsets, and the maximum nbAdditionalBits.
* NOTE: could probably use a larger nbSeq limit
*/
if (isLongOffset || (!usePrefetchDecoder && (totalHistorySize > (1u << 24)) && (nbSeq > 8))) {
ZSTD_OffsetInfo const info = ZSTD_getOffsetInfo(dctx->OFTptr, nbSeq);
if (isLongOffset && info.maxNbAdditionalBits <= STREAM_ACCUMULATOR_MIN) {
/* If isLongOffset, but the maximum number of additional bits that we see in our table is small
* enough, then we know it is impossible to have too long an offset in this block, so we can
* use the regular offset decoder.
*/
isLongOffset = ZSTD_lo_isRegularOffset;
}
if (!usePrefetchDecoder) {
U32 const minShare = MEM_64bits() ? 7 : 20; /* heuristic values, correspond to 2.73% and 7.81% */
usePrefetchDecoder = (info.longOffsetShare >= minShare);
}
}
#endif
dctx->ddictIsCold = 0;
#if !defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \
!defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG)
if (usePrefetchDecoder)
if (usePrefetchDecoder) {
#else
(void)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 */