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ZSTD_execSequence() accepts match in last 7 bytes

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The zstd reference compressor will not emit a match in the last 7
bytes of a block.  The decompressor will also not accept a match
in the last 7 bytes.  This patch makes the decompressor accept a
match in the last 7 bytes.
This commit is contained in:
Nick Terrell 2016-10-21 16:55:26 -07:00
parent 52c1bf93fe
commit eb7873a048
2 changed files with 59 additions and 1 deletions
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10
lib/common/zstd_internal.h
View File

@ -31,6 +31,16 @@
# endif /* __STDC_VERSION__ */
#endif
#ifdef _MSC_VER
# define FORCE_NOINLINE static __declspec(noinline)
#else
# ifdef __GNUC__
# define FORCE_NOINLINE static __attribute__((__noinline__))
# else
# define FORCE_NOINLINE static
# endif
#endif
/*-*************************************
* Dependencies

50
lib/decompress/zstd_decompress.c
View File

@ -840,6 +840,53 @@ static seq_t ZSTD_decodeSequence(seqState_t* seqState)
}
FORCE_NOINLINE
size_t ZSTD_execSequenceLast7(BYTE* op,
BYTE* const oend, seq_t sequence,
const BYTE** litPtr, const BYTE* const litLimit_w,
const BYTE* const base, const BYTE* const vBase, const BYTE* const dictEnd)
{
BYTE* const oLitEnd = op + sequence.litLength;
size_t const sequenceLength = sequence.litLength + sequence.matchLength;
BYTE* const oMatchEnd = op + sequenceLength; /* risk : address space overflow (32-bits) */
BYTE* const oend_w = oend - WILDCOPY_OVERLENGTH;
const BYTE* const iLitEnd = *litPtr + sequence.litLength;
const BYTE* match = oLitEnd - sequence.offset;
/* check */
if (oMatchEnd>oend) return ERROR(dstSize_tooSmall); /* last match must start at a minimum distance of WILDCOPY_OVERLENGTH from oend */
if (iLitEnd > litLimit_w) return ERROR(corruption_detected); /* over-read beyond lit buffer */
if (oLitEnd <= oend_w) return ERROR(GENERIC); /* Precondition */
/* copy literals */
if (op < oend_w) {
ZSTD_wildcopy(op, *litPtr, oend_w - op);
*litPtr += oend_w - op;
op = oend_w;
}
while (op < oLitEnd) *op++ = *(*litPtr)++;
/* copy Match */
if (sequence.offset > (size_t)(oLitEnd - base)) {
/* offset beyond prefix */
if (sequence.offset > (size_t)(oLitEnd - vBase)) return ERROR(corruption_detected);
match = dictEnd - (base-match);
if (match + sequence.matchLength <= dictEnd) {
memmove(oLitEnd, match, sequence.matchLength);
return sequenceLength;
}
/* span extDict & currentPrefixSegment */
{ size_t const length1 = dictEnd - match;
memmove(oLitEnd, match, length1);
op = oLitEnd + length1;
sequence.matchLength -= length1;
match = base;
} }
while (op < oMatchEnd) *op++ = *match++;
return sequenceLength;
}
FORCE_INLINE
size_t ZSTD_execSequence(BYTE* op,
BYTE* const oend, seq_t sequence,
@ -854,8 +901,9 @@ size_t ZSTD_execSequence(BYTE* op,
const BYTE* match = oLitEnd - sequence.offset;
/* check */
if ((oLitEnd>oend_w) | (oMatchEnd>oend)) return ERROR(dstSize_tooSmall); /* last match must start at a minimum distance of WILDCOPY_OVERLENGTH from oend */
if (oMatchEnd>oend) return ERROR(dstSize_tooSmall); /* last match must start at a minimum distance of WILDCOPY_OVERLENGTH from oend */
if (iLitEnd > litLimit_w) return ERROR(corruption_detected); /* over-read beyond lit buffer */
if (oLitEnd>oend_w) return ZSTD_execSequenceLast7(op, oend, sequence, litPtr, litLimit_w, base, vBase, dictEnd);
/* copy Literals */
ZSTD_copy8(op, *litPtr);