AuroraMiddleware/zstd
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backward match extension

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This commit is contained in:
inikep 2016-02-05 19:25:40 +01:00
parent 2712b69582
commit 5b0749715d
1 changed files with 9 additions and 10 deletions
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19
lib/zstd_opt.c
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@ -36,6 +36,8 @@ typedef struct
#define ZSTD_OPT_NUM (1<<12)
#define ZSTD_FREQ_THRESHOLD (256)
// log2_32 is from http://stackoverflow.com/questions/11376288/fast-computing-of-log2-for-64-bit-integers
const int tab32[32] = {
0, 9, 1, 10, 13, 21, 2, 29,
11, 14, 16, 18, 22, 25, 3, 30,
@ -327,15 +329,11 @@ size_t ZSTD_HcGetAllMatches_generic (
match = base + matchIndex;
if (match[minml] == ip[minml]) /* potentially better */
currentMl = ZSTD_count(ip, match, iHighLimit);
#if 0
const BYTE* start = ip;
size_t offset = current - matchIndex;
while ((start > iLowLimit) && (start > base+offset) && (start[-1] == start[-1-offset])) start--;
back = ip - start;
#else
// while ((match-back > base) && (ip-back > iLowLimit) && (ip[-back-1] == match[-back-1])) back++;
#endif
currentMl += back;
if (currentMl > 0) {
while ((match-back > base) && (ip-back > iLowLimit) && (ip[-back-1] == match[-back-1])) back++; /* backward match extension */
currentMl += back;
}
} else {
match = dictBase + matchIndex;
if (MEM_read32(match) == MEM_read32(ip)) /* assumption : matchIndex <= dictLimit-4 (by table construction) */
@ -805,6 +803,7 @@ void ZSTD_compressBlock_opt_generic(ZSTD_CCtx* ctx,
goto _storeSequence;
}
// set prices using matches at position = cur
for (int i = 0; i < match_num; i++)
{
@ -908,7 +907,7 @@ _storeSequence: // cur, last_pos, best_mlen, best_off have to be set
// printf("match="); print_hex_text(ip-offset, mlen, 0);
#if ZSTD_OPT_DEBUG >= 5
size_t ml2;
int ml2;
if (offset)
ml2 = ZSTD_count(ip, ip-offset, iend);
else