ddidderr/zstd-rs
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factored the logic selecting lowest match index

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as suggested by @terrelln
This commit is contained in:
Yann Collet
2019-08-05 15:18:43 +02:00
parent 0b0b83e8f3
commit facbe8b2c2
5 changed files with 19 additions and 21 deletions
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lib/compress/zstd_double_fast.c
+2 -5
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@@ -65,6 +65,7 @@ size_t ZSTD_compressBlock_doubleFast_generic(
const U32 endIndex = (U32)((size_t)(istart - base) + srcSize);
const U32 lowestValid = ms->window.dictLimit;
const U32 maxDistance = 1U << cParams->windowLog;
/* presumes that, if there is a dictionary, it must be using Attach mode */
const U32 prefixLowestIndex = (endIndex - lowestValid > maxDistance) ? endIndex - maxDistance : lowestValid;
const BYTE* const prefixLowest = base + prefixLowestIndex;
const BYTE* const iend = istart + srcSize;
@@ -369,11 +370,7 @@ static size_t ZSTD_compressBlock_doubleFast_extDict_generic(
const BYTE* const ilimit = iend - 8;
const BYTE* const base = ms->window.base;
const U32 endIndex = (U32)((size_t)(istart - base) + srcSize);
const U32 maxDistance = 1U << cParams->windowLog;
const U32 validLowest = ms->window.lowLimit;
const int isDictionary = (ms->loadedDictEnd != 0);
const U32 withinWindow = (endIndex - validLowest > maxDistance) ? endIndex - maxDistance : validLowest;
const U32 lowLimit = isDictionary ? validLowest : withinWindow;
const U32 lowLimit = ZSTD_getLowestMatchIndex(ms, endIndex, cParams->windowLog);
const U32 dictStartIndex = lowLimit;
const U32 dictLimit = ms->window.dictLimit;
const U32 prefixStartIndex = (dictLimit > lowLimit) ? dictLimit : lowLimit;