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

minor compression gain

Browse Source
This commit is contained in:
Yann Collet
2016-01-31 00:58:06 +01:00
parent a6f54ddb2c
commit e93d6ced17
6 changed files with 95 additions and 57 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/zstd_decompress.c
+26 -20
View File
@@ -426,7 +426,7 @@ size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
break;
}
if (litSize+WILDCOPY_OVERLENGTH > srcSize) /* risk reading beyond src buffer with wildcopy */
if (lhSize+litSize+WILDCOPY_OVERLENGTH > srcSize) /* risk reading beyond src buffer with wildcopy */
{
if (litSize > srcSize-lhSize) return ERROR(corruption_detected);
memcpy(dctx->litBuffer, istart+lhSize, litSize);
@@ -483,10 +483,12 @@ size_t ZSTD_decodeSeqHeaders(int* nbSeq, const BYTE** dumpsPtr, size_t* dumpsLen
size_t dumpsLength;
/* check */
if (srcSize < 5) return ERROR(srcSize_wrong);
if (srcSize < MIN_SEQUENCES_SIZE) return ERROR(srcSize_wrong);
/* SeqHead */
*nbSeq = MEM_readLE16(ip); ip+=2;
if (*nbSeq==0) return 2;
LLtype = *ip >> 6;
Offtype = (*ip >> 4) & 3;
MLtype = (*ip >> 2) & 3;
@@ -589,8 +591,8 @@ size_t ZSTD_decodeSeqHeaders(int* nbSeq, const BYTE** dumpsPtr, size_t* dumpsLen
typedef struct {
size_t litLength;
size_t offset;
size_t matchLength;
size_t offset;
} seq_t;
typedef struct {
@@ -603,7 +605,6 @@ typedef struct {
const BYTE* dumpsEnd;
} seqState_t;
static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState)
{
size_t litLength;
@@ -614,7 +615,7 @@ static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState)
const BYTE* const de = seqState->dumpsEnd;
/* Literal length */
litLength = FSE_decodeSymbol(&(seqState->stateLL), &(seqState->DStream));
litLength = FSE_peakSymbol(&(seqState->stateLL));
prevOffset = litLength ? seq->offset : seqState->prevOffset;
if (litLength == MaxLL) {
U32 add = *dumps++;
@@ -632,17 +633,20 @@ static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState)
1 /*fake*/, 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, /*fake*/ 1, 1, 1, 1, 1 };
U32 offsetCode, nbBits;
offsetCode = FSE_decodeSymbol(&(seqState->stateOffb), &(seqState->DStream)); /* <= maxOff, by table construction */
if (MEM_32bits()) BIT_reloadDStream(&(seqState->DStream));
nbBits = offsetCode - 1;
U32 offsetCode = FSE_peakSymbol(&(seqState->stateOffb)); /* <= maxOff, by table construction */
U32 nbBits = offsetCode - 1;
if (offsetCode==0) nbBits = 0; /* cmove */
offset = offsetPrefix[offsetCode] + BIT_readBits(&(seqState->DStream), nbBits);
if (MEM_32bits()) BIT_reloadDStream(&(seqState->DStream));
if (offsetCode==0) offset = prevOffset; /* cmove */
if (offsetCode==0) offset = prevOffset; /* repcode, cmove */
if (offsetCode | !litLength) seqState->prevOffset = seq->offset; /* cmove */
FSE_decodeSymbol(&(seqState->stateOffb), &(seqState->DStream)); /* update */
}
/* Literal length update */
FSE_decodeSymbol(&(seqState->stateLL), &(seqState->DStream)); /* update */
if (MEM_32bits()) BIT_reloadDStream(&(seqState->DStream));
/* MatchLength */
matchLength = FSE_decodeSymbol(&(seqState->stateML), &(seqState->DStream));
if (matchLength == MaxML) {
@@ -778,7 +782,7 @@ static size_t ZSTD_decompressSequences(
ip += errorCode;
/* Regen sequences */
{
if (nbSeq) {
seq_t sequence;
seqState_t seqState;
@@ -803,16 +807,18 @@ static size_t ZSTD_decompressSequences(
}
/* check if reached exact end */
if ( !BIT_endOfDStream(&(seqState.DStream)) ) return ERROR(corruption_detected); /* DStream should be entirely and exactly consumed; otherwise data is corrupted */
if (nbSeq)
return ERROR(corruption_detected); /* DStream should be entirely and exactly consumed; otherwise data is corrupted */
}
/* last literal segment */
{
size_t lastLLSize = litEnd - litPtr;
if (litPtr > litEnd) return ERROR(corruption_detected);
if (op+lastLLSize > oend) return ERROR(dstSize_tooSmall);
if (op != litPtr) memcpy(op, litPtr, lastLLSize);
op += lastLLSize;
} }
/* last literal segment */
{
size_t lastLLSize = litEnd - litPtr;
if (litPtr > litEnd) return ERROR(corruption_detected); /* too many literals already used */
if (op+lastLLSize > oend) return ERROR(dstSize_tooSmall);
memcpy(op, litPtr, lastLLSize);
op += lastLLSize;
}
return op-ostart;
}