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small decompression speed improvement

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This commit is contained in:
Yann Collet 2015-10-19 02:36:34 +01:00
parent 107c5755f4
commit c7ae9ffde3
1 changed files with 6 additions and 3 deletions
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9
lib/zstd.c
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@ -114,7 +114,7 @@ static const U32 g_searchStrength = 8;
#define Offbits 5 #define Offbits 5
#define MaxML ((1<<MLbits )-1) #define MaxML ((1<<MLbits )-1)
#define MaxLL ((1<<LLbits )-1) #define MaxLL ((1<<LLbits )-1)
#define MaxOff ((1<<Offbits)-1) #define MaxOff 26
#define LitFSELog 11 #define LitFSELog 11
#define MLFSELog 10 #define MLFSELog 10
#define LLFSELog 10 #define LLFSELog 10
@ -1269,12 +1269,15 @@ static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState)
/* Offset */ /* Offset */
{ {
static const size_t offsetPrefix[MaxOff+1] = { 1, 1, 2, 4, 8, 16, 32, 64, 128, 256,
512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144,
524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432 };
U32 offsetCode, nbBits; U32 offsetCode, nbBits;
offsetCode = FSE_decodeSymbol(&(seqState->stateOffb), &(seqState->DStream)); offsetCode = FSE_decodeSymbol(&(seqState->stateOffb), &(seqState->DStream)); /* <= maxOff, by table construction */
if (MEM_32bits()) BIT_reloadDStream(&(seqState->DStream)); if (MEM_32bits()) BIT_reloadDStream(&(seqState->DStream));
nbBits = offsetCode - 1; nbBits = offsetCode - 1;
if (offsetCode==0) nbBits = 0; /* cmove */ if (offsetCode==0) nbBits = 0; /* cmove */
offset = ((size_t)1 << (nbBits & ((sizeof(offset)*8)-1))) + BIT_readBits(&(seqState->DStream), nbBits); offset = offsetPrefix[offsetCode] + BIT_readBits(&(seqState->DStream), nbBits);
if (MEM_32bits()) BIT_reloadDStream(&(seqState->DStream)); if (MEM_32bits()) BIT_reloadDStream(&(seqState->DStream));
if (offsetCode==0) offset = prevOffset; /* cmove */ if (offsetCode==0) offset = prevOffset; /* cmove */
} }