AuroraMiddleware/zstd
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decide long-offset mode based on offcode statistics

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threshold vaguely estimated
This commit is contained in:
Yann Collet 2018-02-09 12:33:28 -08:00
parent de68c2ff10
commit 64ee732694
1 changed files with 38 additions and 23 deletions
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61
lib/decompress/zstd_decompress.c
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@ -1082,7 +1082,7 @@ size_t ZSTD_execSequence(BYTE* op,
static size_t ZSTD_decompressSequences(
ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset)
{
const BYTE* ip = (const BYTE*)seqStart;
@ -1095,16 +1095,8 @@ static size_t ZSTD_decompressSequences(
const BYTE* const base = (const BYTE*) (dctx->base);
const BYTE* const vBase = (const BYTE*) (dctx->vBase);
const BYTE* const dictEnd = (const BYTE*) (dctx->dictEnd);
int nbSeq;
DEBUGLOG(5, "ZSTD_decompressSequences");
/* Build Decoding Tables */
{ size_t const seqHSize = ZSTD_decodeSeqHeaders(dctx, &nbSeq, ip, seqSize);
DEBUGLOG(5, "ZSTD_decodeSeqHeaders: size=%u, nbSeq=%i",
(U32)seqHSize, nbSeq);
if (ZSTD_isError(seqHSize)) return seqHSize;
ip += seqHSize;
}
DEBUGLOG(5, "ZSTD_decompressSequences");
/* Regen sequences */
if (nbSeq) {
@ -1328,7 +1320,7 @@ size_t ZSTD_execSequenceLong(BYTE* op,
static size_t ZSTD_decompressSequencesLong(
ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
const void* seqStart, size_t seqSize,
const void* seqStart, size_t seqSize, int nbSeq,
const ZSTD_longOffset_e isLongOffset)
{
const BYTE* ip = (const BYTE*)seqStart;
@ -1341,13 +1333,6 @@ static size_t ZSTD_decompressSequencesLong(
const BYTE* const prefixStart = (const BYTE*) (dctx->base);
const BYTE* const dictStart = (const BYTE*) (dctx->vBase);
const BYTE* const dictEnd = (const BYTE*) (dctx->dictEnd);
int nbSeq;
/* Build Decoding Tables */
{ size_t const seqHSize = ZSTD_decodeSeqHeaders(dctx, &nbSeq, ip, seqSize);
if (ZSTD_isError(seqHSize)) return seqHSize;
ip += seqHSize;
}
/* Regen sequences */
if (nbSeq) {
@ -1408,6 +1393,24 @@ static size_t ZSTD_decompressSequencesLong(
}
static unsigned
ZSTD_shareLongOffsets(const FSE_DTable* offTable)
{
U32 const tableLog = ((const FSE_DTableHeader*)offTable)[0].tableLog;
const FSE_decode_t* table = (const FSE_decode_t*)(offTable + 1);
U32 const max = 1 << tableLog;
U32 u, total = 0;
assert(tableLog <= OffFSELog);
for (u=0; u<max; u++)
if (table[u].symbol > 23) total += 1;
total <<= (OffFSELog - tableLog);
return total;
}
static size_t ZSTD_decompressBlock_internal(ZSTD_DCtx* dctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize, const int frame)
@ -1430,11 +1433,23 @@ static size_t ZSTD_decompressBlock_internal(ZSTD_DCtx* dctx,
ip += litCSize;
srcSize -= litCSize;
}
if ( frame /* windowSize exists */
&& (dctx->fParams.windowSize > (1<<24))
&& MEM_64bits() /* x86 benefits less from long mode than x64 */ )
return ZSTD_decompressSequencesLong(dctx, dst, dstCapacity, ip, srcSize, isLongOffset);
return ZSTD_decompressSequences(dctx, dst, dstCapacity, ip, srcSize, isLongOffset);
/* Build Decoding Tables */
{ int nbSeq;
size_t const seqHSize = ZSTD_decodeSeqHeaders(dctx, &nbSeq, ip, srcSize);
if (ZSTD_isError(seqHSize)) return seqHSize;
ip += seqHSize;
srcSize -= seqHSize;
if (dctx->fParams.windowSize > (1<<24)) {
U32 const shareLongOffsets = ZSTD_shareLongOffsets(dctx->entropy.OFTable);
U32 const minShare = MEM_64bits() ? 12 : 20;
if (shareLongOffsets >= minShare)
return ZSTD_decompressSequencesLong(dctx, dst, dstCapacity, ip, srcSize, nbSeq, isLongOffset);
}
return ZSTD_decompressSequences(dctx, dst, dstCapacity, ip, srcSize, nbSeq, isLongOffset);
}
}