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refactored decompression

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This commit is contained in:
Yann Collet 2015-11-19 17:13:19 +01:00
parent 110cc14bab
commit b3a2af970e
1 changed files with 81 additions and 79 deletions
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160
lib/zstd_decompress.c
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@ -35,8 +35,9 @@
*****************************************************************/
/*!
* HEAPMODE :
* Select how default functions will allocate memory for their context,
* Select how default compression functions will allocate memory for their hash table,
* in memory stack (0, fastest), or in memory heap (1, requires malloc())
* Note that compression context is fairly large, as a consequence heap memory is recommended.
*/
#ifndef ZSTD_HEAPMODE
# define ZSTD_HEAPMODE 1
@ -392,10 +393,6 @@ typedef struct {
} seqState_t;
/** ZSTD_decodeSequence
* Decode the next sequence, defined as nbLiterals, PtrToLiterals, nbMatches, Offset
* @seq : store sequence into this seq_t
*/
static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState)
{
size_t litLength;
@ -461,18 +458,18 @@ static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState)
FORCE_INLINE size_t ZSTD_execSequence(BYTE* op,
seq_t sequence,
BYTE* const oend, seq_t sequence,
const BYTE** litPtr, const BYTE* const litLimit_8,
BYTE* const base, BYTE* const vBase, BYTE* const dictEnd,
BYTE* const oend)
BYTE* const base, BYTE* const vBase, BYTE* const dictEnd)
{
static const int dec32table[] = {0, 1, 2, 1, 4, 4, 4, 4}; /* added */
static const int dec64table[] = {8, 8, 8, 7, 8, 9,10,11}; /* substracted */
const BYTE* const ostart = op;
static const int dec32table[] = { 0, 1, 2, 1, 4, 4, 4, 4 }; /* added */
static const int dec64table[] = { 8, 8, 8, 7, 8, 9,10,11 }; /* substracted */
BYTE* const oLitEnd = op + sequence.litLength;
BYTE* const oMatchEnd = op + sequence.litLength + sequence.matchLength; /* risk : address space overflow (32-bits) */
const size_t sequenceLength = sequence.litLength + sequence.matchLength;
BYTE* const oMatchEnd = op + sequenceLength; /* risk : address space overflow (32-bits) */
BYTE* const oend_8 = oend-8;
const BYTE* const litEnd = *litPtr + sequence.litLength;
const BYTE* match = oLitEnd - sequence.offset;
/* check */
if (oLitEnd > oend_8) return ERROR(dstSize_tooSmall); /* last match must start at a minimum distance of 8 from oend */
@ -485,74 +482,67 @@ FORCE_INLINE size_t ZSTD_execSequence(BYTE* op,
*litPtr = litEnd; /* update for next sequence */
/* copy Match */
{
const BYTE* match = op - sequence.offset;
/* check */
//if (match > oLitEnd) return ERROR(corruption_detected); /* address space overflow test (is clang optimizer wrongly removing this test ?) */
if (sequence.offset > (size_t)oLitEnd) return ERROR(corruption_detected); /* address space overflow test (this test seems preserved by clang optimizer) */
/* check */
//if (match > op) return ERROR(corruption_detected); /* address space overflow test (is clang optimizer wrongly removing this test ?) */
if (sequence.offset > (size_t)op) return ERROR(corruption_detected); /* address space overflow test (this test seems kept by clang optimizer) */
if (match < base)
{
/* offset beyond prefix */
if (match < vBase) return ERROR(corruption_detected);
match = dictEnd - (base-match);
if (match + sequence.matchLength <= dictEnd)
{
memcpy(oLitEnd, match, sequence.matchLength);
return sequenceLength;
}
/* span extDict & currentPrefixSegment */
{
size_t length1 = dictEnd - match;
memcpy(oLitEnd, match, length1);
op = oLitEnd + length1;
sequence.matchLength -= length1;
match = base;
}
}
if (match < base)
{
/* offset beyond prefix */
if (match < vBase) return ERROR(corruption_detected);
match = dictEnd - (base-match);
if (match + sequence.matchLength <= dictEnd)
{
memcpy(op, match, sequence.matchLength);
return oMatchEnd - ostart;
}
/* span extDict & currentPrefixSegment */
{
size_t length1 = dictEnd - match;
memcpy(op, match, length1);
op += length1;
sequence.matchLength -= length1;
match = base;
}
}
{
/* match within prefix */
if (sequence.offset < 8)
{
/* close range match, overlap */
const int dec64 = dec64table[sequence.offset];
op[0] = match[0];
op[1] = match[1];
op[2] = match[2];
op[3] = match[3];
match += dec32table[sequence.offset];
ZSTD_copy4(op+4, match);
match -= dec64;
}
else
{
ZSTD_copy8(op, match);
}
op += 8; match += 8;
if (oMatchEnd > oend-12)
{
if (op < oend_8)
{
ZSTD_wildcopy(op, match, oend_8 - op);
match += oend_8 - op;
op = oend_8;
}
while (op < oMatchEnd) *op++ = *match++;
}
else
{
ZSTD_wildcopy(op, match, sequence.matchLength-8); /* works even if matchLength < 8 */
}
return oMatchEnd - ostart;
}
}
/* match within prefix */
if (sequence.offset < 8)
{
/* close range match, overlap */
const int sub2 = dec64table[sequence.offset];
op[0] = match[0];
op[1] = match[1];
op[2] = match[2];
op[3] = match[3];
match += dec32table[sequence.offset];
ZSTD_copy4(op+4, match);
match -= sub2;
}
else
{
ZSTD_copy8(op, match);
}
op += 8; match += 8;
if (oMatchEnd > oend-12)
{
if (op < oend_8)
{
ZSTD_wildcopy(op, match, oend_8 - op);
match += oend_8 - op;
op = oend_8;
}
while (op < oMatchEnd) *op++ = *match++;
}
else
{
ZSTD_wildcopy(op, match, sequence.matchLength-8); /* works even if matchLength < 8 */
}
return sequenceLength;
}
static size_t ZSTD_decompressSequences(
ZSTD_DCtx* dctx,
void* dst, size_t maxDstSize,
@ -599,19 +589,31 @@ static size_t ZSTD_decompressSequences(
FSE_initDState(&(seqState.stateOffb), &(seqState.DStream), DTableOffb);
FSE_initDState(&(seqState.stateML), &(seqState.DStream), DTableML);
for ( ; (BIT_reloadDStream(&(seqState.DStream)) <= BIT_DStream_completed) && (nbSeq>0) ; )
for ( ; (BIT_reloadDStream(&(seqState.DStream)) < BIT_DStream_completed) ; )
{
size_t oneSeqSize;
nbSeq--;
ZSTD_decodeSequence(&sequence, &seqState);
oneSeqSize = ZSTD_execSequence(op, sequence, &litPtr, litLimit_8, base, vBase, dictEnd, oend);
oneSeqSize = ZSTD_execSequence(op, oend, sequence, &litPtr, litLimit_8, base, vBase, dictEnd);
if (ZSTD_isError(oneSeqSize)) return oneSeqSize;
op += oneSeqSize;
}
if (nbSeq<0) return ERROR(corruption_detected); /* requested too many sequences : data is corrupted */
/* now BIT_reloadDStream(&(seqState.DStream)) >= BIT_DStream_completed) */
for ( ; (BIT_reloadDStream(&(seqState.DStream)) == BIT_DStream_completed) && nbSeq ; )
{
size_t oneSeqSize;
nbSeq--;
ZSTD_decodeSequence(&sequence, &seqState);
oneSeqSize = ZSTD_execSequence(op, oend, sequence, &litPtr, litLimit_8, base, vBase, dictEnd);
if (ZSTD_isError(oneSeqSize)) return oneSeqSize;
op += oneSeqSize;
}
/* check if reached exact end */
if ( !BIT_endOfDStream(&(seqState.DStream)) ) return ERROR(corruption_detected); /* requested too much : data is corrupted */
if (nbSeq<0) return ERROR(corruption_detected); /* requested too many sequences : data is corrupted */
if ( !BIT_endOfDStream(&(seqState.DStream)) ) return ERROR(corruption_detected); /* DStream should be entirely and precisely consumed; otherwise data is corrupted */
/* last literal segment */
{