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strengthened bufferless streaming decompression

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This commit is contained in:
Yann Collet
2015-12-05 09:23:53 +01:00
parent 1c2ddba469
commit e47c4e5f8e
4 changed files with 49 additions and 18 deletions
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lib/zstd_compress.c
+11 -11
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@@ -769,12 +769,12 @@ size_t ZSTD_compressBlock_fast_generic(ZSTD_CCtx* zc,
/* init */
ZSTD_resetSeqStore(seqStorePtr);
if (ip < base+4)
if (ip < lowest+4)
{
hashTable[ZSTD_hashPtr(base+1, hBits, mls)] = 1;
hashTable[ZSTD_hashPtr(base+2, hBits, mls)] = 2;
hashTable[ZSTD_hashPtr(base+3, hBits, mls)] = 3;
ip = base+4;
hashTable[ZSTD_hashPtr(lowest+1, hBits, mls)] = zc->dictLimit+1;
hashTable[ZSTD_hashPtr(lowest+2, hBits, mls)] = zc->dictLimit+2;
hashTable[ZSTD_hashPtr(lowest+3, hBits, mls)] = zc->dictLimit+3;
ip = lowest+4;
}
/* Main Search Loop */
@@ -1535,6 +1535,7 @@ size_t ZSTD_compressBlock_lazy_generic(ZSTD_CCtx* ctx,
const BYTE* anchor = istart;
const BYTE* const iend = istart + srcSize;
const BYTE* const ilimit = iend - 8;
const BYTE* const base = ctx->base + ctx->dictLimit;
size_t offset_2=REPCODE_STARTVALUE, offset_1=REPCODE_STARTVALUE;
const U32 maxSearches = 1 << ctx->params.searchLog;
@@ -1547,7 +1548,7 @@ size_t ZSTD_compressBlock_lazy_generic(ZSTD_CCtx* ctx,
/* init */
ZSTD_resetSeqStore(seqStorePtr);
if (((ip-ctx->base) - ctx->dictLimit) < REPCODE_STARTVALUE) ip += REPCODE_STARTVALUE;
if ((ip-base) < REPCODE_STARTVALUE) ip = base + REPCODE_STARTVALUE;
/* Match Loop */
while (ip < ilimit)
@@ -1572,7 +1573,7 @@ size_t ZSTD_compressBlock_lazy_generic(ZSTD_CCtx* ctx,
matchLength = ml2, start = ip, offset=offsetFound;
}
if (matchLength < MINMATCH)
if (matchLength < MINMATCH)
{
ip += ((ip-anchor) >> g_searchStrength) + 1; /* jump faster over incompressible sections */
continue;
@@ -1633,7 +1634,7 @@ size_t ZSTD_compressBlock_lazy_generic(ZSTD_CCtx* ctx,
/* catch up */
if (offset)
{
while ((start>anchor) && (start>ctx->base+offset) && (start[-1] == start[-1-offset])) /* only search for offset within prefix */
while ((start>anchor) && (start>base+offset) && (start[-1] == start[-1-offset])) /* only search for offset within prefix */
{ start--; matchLength++; }
offset_2 = offset_1; offset_1 = offset;
}
@@ -1990,7 +1991,6 @@ size_t ZSTD_compressContinue (ZSTD_CCtx* zc,
void* dst, size_t dstSize,
const void* src, size_t srcSize)
{
U32 adressOverflow = 0;
const BYTE* const ip = (const BYTE*) src;
/* Check if blocks follow each other */
@@ -2001,13 +2001,13 @@ size_t ZSTD_compressContinue (ZSTD_CCtx* zc,
zc->lowLimit = zc->dictLimit;
zc->dictLimit = (U32)(zc->nextSrc - zc->base);
zc->dictBase = zc->base;
if ((size_t)zc->base < delta) adressOverflow = zc->lowLimit;
zc->base -= delta;
zc->nextToUpdate = zc->dictLimit;
if (zc->dictLimit - zc->lowLimit < 8) zc->lowLimit = zc->dictLimit; /* too small extDict */
}
/* preemptive overflow correction */
if (adressOverflow || (zc->lowLimit > (1<<30) ))
if ((zc->base > ip) || (zc->lowLimit > (1<<30) ))
{
U32 correction = zc->lowLimit-1;
ZSTD_reduceIndex(zc, correction);