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Correct and clarify repcode offset history logic

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This commit is contained in:
Elliot Gorokhovsky
2022-05-09 21:01:38 -04:00
parent 8bf32de850
commit 97aabc496e
3 changed files with 42 additions and 26 deletions
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lib/compress/zstd_double_fast.c
+11 -8
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@@ -67,7 +67,7 @@ size_t ZSTD_compressBlock_doubleFast_noDict_generic(
const BYTE* const iend = istart + srcSize;
const BYTE* const ilimit = iend - HASH_READ_SIZE;
U32 offset_1=rep[0], offset_2=rep[1];
U32 offsetSaved = 0;
U32 offsetSaved1 = 0, offsetSaved2 = 0;
size_t mLength;
U32 offset;
@@ -100,8 +100,8 @@ size_t ZSTD_compressBlock_doubleFast_noDict_generic(
U32 const current = (U32)(ip - base);
U32 const windowLow = ZSTD_getLowestPrefixIndex(ms, current, cParams->windowLog);
U32 const maxRep = current - windowLow;
if (offset_2 > maxRep) offsetSaved = offset_2, offset_2 = 0;
if (offset_1 > maxRep) offsetSaved = offset_1, offset_1 = 0;
if (offset_2 > maxRep) offsetSaved2 = offset_2, offset_2 = 0;
if (offset_1 > maxRep) offsetSaved1 = offset_1, offset_1 = 0;
}
/* Outer Loop: one iteration per match found and stored */
@@ -175,9 +175,13 @@ size_t ZSTD_compressBlock_doubleFast_noDict_generic(
} while (ip1 <= ilimit);
_cleanup:
/* If rep_offset1 started invalid (offsetSaved1 > 0) and became valid (rep_offset1 > 0),
* rotate saved offsets. */
offsetSaved2 = ((offsetSaved1 > 0) & (offset_1 > 0)) ? offsetSaved1 : offsetSaved2;
/* save reps for next block */
rep[0] = offset_1 ? offset_1 : offsetSaved;
rep[1] = offset_2 ? offset_2 : offsetSaved;
rep[0] = offset_1 ? offset_1 : offsetSaved1;
rep[1] = offset_2 ? offset_2 : offsetSaved2;
/* Return the last literals size */
return (size_t)(iend - anchor);
@@ -275,7 +279,6 @@ size_t ZSTD_compressBlock_doubleFast_dictMatchState_generic(
const BYTE* const iend = istart + srcSize;
const BYTE* const ilimit = iend - HASH_READ_SIZE;
U32 offset_1=rep[0], offset_2=rep[1];
U32 offsetSaved = 0;
const ZSTD_matchState_t* const dms = ms->dictMatchState;
const ZSTD_compressionParameters* const dictCParams = &dms->cParams;
@@ -461,8 +464,8 @@ _match_stored:
} /* while (ip < ilimit) */
/* save reps for next block */
rep[0] = offset_1 ? offset_1 : offsetSaved;
rep[1] = offset_2 ? offset_2 : offsetSaved;
rep[0] = offset_1;
rep[1] = offset_2;
/* Return the last literals size */
return (size_t)(iend - anchor);