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Fix compression failure on incompressible data

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If the destination buffer is the minimum allowed size in
`ZSTD_compressSequences()` (2^17), then if the block isn't compressible
compression might fail with `dstSize_tooSmall`, when it should instead emit
a raw uncompressed block.

Additionally, `ZSTD_compressLiterals()` implicitly called
`ZSTD_noCompressLiterals()` if Huffman compression failed. Make that
explicit.
This commit is contained in:
Nick Terrell 2017-08-03 14:05:01 -07:00
parent ee27f6937c
commit 308047eb5d
1 changed files with 34 additions and 18 deletions
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52
lib/compress/zstd_compress.c
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@ -942,7 +942,7 @@ static size_t ZSTD_compressLiterals (ZSTD_entropyCTables_t * entropy,
else { entropy->hufCTable_repeatMode = HUF_repeat_check; } /* now have a table to reuse */
}
if ((cLitSize==0) | (cLitSize >= srcSize - minGain)) {
if ((cLitSize==0) | (cLitSize >= srcSize - minGain) | ERR_isError(cLitSize)) {
entropy->hufCTable_repeatMode = HUF_repeat_none;
return ZSTD_noCompressLiterals(dst, dstCapacity, src, srcSize);
}
@ -1156,11 +1156,10 @@ MEM_STATIC size_t ZSTD_encodeSequences(void* dst, size_t dstCapacity,
}
}
MEM_STATIC size_t ZSTD_compressSequences (seqStore_t* seqStorePtr,
MEM_STATIC size_t ZSTD_compressSequences_internal(seqStore_t* seqStorePtr,
ZSTD_entropyCTables_t* entropy,
ZSTD_compressionParameters const* cParams,
void* dst, size_t dstCapacity,
size_t srcSize)
void* dst, size_t dstCapacity)
{
const int longOffsets = cParams->windowLog > STREAM_ACCUMULATOR_MIN;
U32 count[MaxSeq+1];
@ -1195,7 +1194,7 @@ MEM_STATIC size_t ZSTD_compressSequences (seqStore_t* seqStorePtr,
if (nbSeq < 0x7F) *op++ = (BYTE)nbSeq;
else if (nbSeq < LONGNBSEQ) op[0] = (BYTE)((nbSeq>>8) + 0x80), op[1] = (BYTE)nbSeq, op+=2;
else op[0]=0xFF, MEM_writeLE16(op+1, (U16)(nbSeq - LONGNBSEQ)), op+=3;
if (nbSeq==0) goto _check_compressibility;
if (nbSeq==0) return op - ostart;
/* seqHead : flags for FSE encoding type */
seqHead = op++;
@ -1244,23 +1243,40 @@ MEM_STATIC size_t ZSTD_compressSequences (seqStore_t* seqStorePtr,
op += streamSize;
}
return op - ostart;
}
/* check compressibility */
_check_compressibility:
{ size_t const minGain = ZSTD_minGain(srcSize);
size_t const maxCSize = srcSize - minGain;
if ((size_t)(op-ostart) >= maxCSize) {
entropy->hufCTable_repeatMode = HUF_repeat_none;
entropy->offcode_repeatMode = FSE_repeat_none;
entropy->matchlength_repeatMode = FSE_repeat_none;
entropy->litlength_repeatMode = FSE_repeat_none;
return 0;
} }
MEM_STATIC size_t ZSTD_compressSequences(seqStore_t* seqStorePtr,
ZSTD_entropyCTables_t* entropy,
ZSTD_compressionParameters const* cParams,
void* dst, size_t dstCapacity,
size_t srcSize)
{
size_t const cSize = ZSTD_compressSequences_internal(seqStorePtr, entropy, cParams,
dst, dstCapacity);
size_t const minGain = ZSTD_minGain(srcSize);
size_t const maxCSize = srcSize - minGain;
/* If the srcSize <= dstCapacity, then there is enough space to write a
* raw uncompressed block. Since we ran out of space, the block must not
* be compressible, so fall back to a raw uncompressed block.
*/
int const uncompressibleError = cSize == ERROR(dstSize_tooSmall) && srcSize <= dstCapacity;
if (ZSTD_isError(cSize) && !uncompressibleError)
return cSize;
/* Check compressibility */
if (cSize >= maxCSize || uncompressibleError) {
entropy->hufCTable_repeatMode = HUF_repeat_none;
entropy->offcode_repeatMode = FSE_repeat_none;
entropy->matchlength_repeatMode = FSE_repeat_none;
entropy->litlength_repeatMode = FSE_repeat_none;
return 0;
}
assert(!ZSTD_isError(cSize));
/* confirm repcodes */
{ int i; for (i=0; i<ZSTD_REP_NUM; i++) seqStorePtr->rep[i] = seqStorePtr->repToConfirm[i]; }
return op - ostart;
return cSize;
}