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Merge pull request #2338 from terrelln/comments

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Add comments to ZSTD_getLowest{Match,Prefix}Index()
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Nick Terrell 2020-10-01 18:56:24 -07:00 committed by GitHub
commit 4b4d8b4dc9
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7
lib/compress/zstd_compress_internal.h
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@ -1001,6 +1001,10 @@ MEM_STATIC U32 ZSTD_getLowestMatchIndex(const ZSTD_matchState_t* ms, U32 curr, u
U32 const lowestValid = ms->window.lowLimit;
U32 const withinWindow = (curr - lowestValid > maxDistance) ? curr - maxDistance : lowestValid;
U32 const isDictionary = (ms->loadedDictEnd != 0);
/* When using a dictionary the entire dictionary is valid if a single byte of the dictionary
* is within the window. We invalidate the dictionary (and set loadedDictEnd to 0) when it isn't
* valid for the entire block. So this check is sufficient to find the lowest valid match index.
*/
U32 const matchLowest = isDictionary ? lowestValid : withinWindow;
return matchLowest;
}
@ -1014,6 +1018,9 @@ MEM_STATIC U32 ZSTD_getLowestPrefixIndex(const ZSTD_matchState_t* ms, U32 curr,
U32 const lowestValid = ms->window.dictLimit;
U32 const withinWindow = (curr - lowestValid > maxDistance) ? curr - maxDistance : lowestValid;
U32 const isDictionary = (ms->loadedDictEnd != 0);
/* When computing the lowest prefix index we need to take the dictionary into account to handle
* the edge case where the dictionary and the source are contiguous in memory.
*/
U32 const matchLowest = isDictionary ? lowestValid : withinWindow;
return matchLowest;
}