ddidderr/zstd-rs
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

improved decoding speed (660)

Browse Source
This commit is contained in:
Yann Collet
2016-03-23 13:57:49 +01:00
parent fd69225086
commit afab02098a
2 changed files with 15 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/bitstream.h
+10 -2
View File
@@ -285,6 +285,14 @@ MEM_STATIC size_t BIT_initDStream(BIT_DStream_t* bitD, const void* srcBuffer, si
return srcSize; return srcSize;
} }
MEM_STATIC size_t BIT_consumeFirstBits(size_t* bitDPtr, U32 const nbBits)
{
static const unsigned mask[] = { 0, 1, 3, 7, 0xF, 0x1F, 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF, 0x1FFFF, 0x3FFFF, 0x7FFFF, 0xFFFFF, 0x1FFFFF, 0x3FFFFF, 0x7FFFFF, 0xFFFFFF, 0x1FFFFFF, 0x3FFFFFF }; /* up to 26 bits */
size_t const result = *bitDPtr & mask[nbBits];
*bitDPtr >>= nbBits;
return result;
}
/*! BIT_lookBits() : /*! BIT_lookBits() :
* Provides next n bits from local register. * Provides next n bits from local register.
* local register is not modified (bits are still present for next read/look). * local register is not modified (bits are still present for next read/look).
@@ -318,7 +326,7 @@ MEM_STATIC void BIT_skipBits(BIT_DStream_t* bitD, U32 nbBits)
*/ */
MEM_STATIC size_t BIT_readBits(BIT_DStream_t* bitD, U32 nbBits) MEM_STATIC size_t BIT_readBits(BIT_DStream_t* bitD, U32 nbBits)
{ {
size_t value = BIT_lookBits(bitD, nbBits); size_t const value = BIT_lookBits(bitD, nbBits);
BIT_skipBits(bitD, nbBits); BIT_skipBits(bitD, nbBits);
return value; return value;
} }
@@ -327,7 +335,7 @@ MEM_STATIC size_t BIT_readBits(BIT_DStream_t* bitD, U32 nbBits)
* unsafe version; only works only if nbBits >= 1 */ * unsafe version; only works only if nbBits >= 1 */
MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, U32 nbBits) MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, U32 nbBits)
{ {
size_t value = BIT_lookBitsFast(bitD, nbBits); size_t const value = BIT_lookBitsFast(bitD, nbBits);
BIT_skipBits(bitD, nbBits); BIT_skipBits(bitD, nbBits);
return value; return value;
} }
lib/zstd_decompress.c
+5 -3
View File
@@ -652,16 +652,18 @@ static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState, const U32 mls)
0x8000, 0x10000, 0x20000, 0x40000, 0x80000, 0x100000, 0x200000, 0x400000, 0x8000, 0x10000, 0x20000, 0x40000, 0x80000, 0x100000, 0x200000, 0x400000,
0x800000, 0x1000000, 0x2000000, 0x4000000, /*fake*/ 1, 1, 1, 1 }; 0x800000, 0x1000000, 0x2000000, 0x4000000, /*fake*/ 1, 1, 1, 1 };
seq->litLength = LL_base[llCode] + BIT_readBits(&(seqState->DStream), llBits); size_t allBits = BIT_readBits(&(seqState->DStream), llBits+mlBits+ofBits);
seq->matchLength = ML_base[mlCode] + BIT_readBits(&(seqState->DStream), mlBits) + mls;
/* Offset */ /* Offset */
{ size_t const offset = ofCode ? OF_base[ofCode] + BIT_readBits(&(seqState->DStream), ofBits) : { size_t const offset = ofCode ? OF_base[ofCode] + BIT_consumeFirstBits(&allBits, ofBits) :
llCode ? seq->offset : seqState->prevOffset; llCode ? seq->offset : seqState->prevOffset;
if (ofCode | !llCode) seqState->prevOffset = seq->offset; /* cmove */ if (ofCode | !llCode) seqState->prevOffset = seq->offset; /* cmove */
seq->offset = offset; seq->offset = offset;
} }
seq->matchLength = ML_base[mlCode] + BIT_consumeFirstBits(&allBits, mlBits) + mls;
seq->litLength = LL_base[llCode] + BIT_consumeFirstBits(&allBits, llBits);
/* ANS state update */ /* ANS state update */
FSE_updateState(&(seqState->stateLL), &(seqState->DStream)); FSE_updateState(&(seqState->stateLL), &(seqState->DStream));
FSE_updateState(&(seqState->stateML), &(seqState->DStream)); FSE_updateState(&(seqState->stateML), &(seqState->DStream));