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Remove bubbling down matches with longer offCode and same matchLen

dev
senhuang42 2020-10-04 21:48:39 -04:00
parent 031b7ec15f
commit 0325d878f2
1 changed files with 6 additions and 29 deletions
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27
lib/compress/zstd_opt.c
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@ -882,38 +882,15 @@ static void ZSTD_opt_maybeAddLdm(ZSTD_match_t* matches, U32* nbMatches,
matches[*nbMatches].off = candidateOffCode;
(*nbMatches)++;
} else if ((candidateMatchLength >= matches[*nbMatches-1].len) && *nbMatches < ZSTD_OPT_NUM) {
/* Maintain order of matches, which is firstly - increasing in matchlength,
* and secondly - decreasing in offCode. Since matches from the ldm seq store are likely
* to be the longest match found, we simply start at the end of the array and bubble
* the ldm match down as necessary.
*/
if (candidateMatchLength == matches[*nbMatches-1].len) {
U32 candidateMatchIdx;
if (candidateOffCode == matches[*nbMatches-1].off) {
/* No need to insert the match if it's the exact same */
/* No need to insert the match if it's the exact same, or offCode is larger with same matchLen */
if (candidateMatchLength == matches[*nbMatches-1].len && candidateOffCode >= matches[*nbMatches-1].off) {
return;
}
candidateMatchIdx = *nbMatches;
matches[*nbMatches].len = candidateMatchLength;
matches[*nbMatches].off = candidateOffCode;
if (candidateOffCode != matches[*nbMatches-1].off) {
while (candidateMatchIdx > 0 &&
matches[candidateMatchIdx].off > matches[candidateMatchIdx - 1].off &&
matches[candidateMatchIdx].len == matches[candidateMatchIdx - 1].len) {
ZSTD_match_t tmp = matches[candidateMatchIdx - 1];
matches[candidateMatchIdx - 1] = matches[candidateMatchIdx];
matches[candidateMatchIdx] = tmp;
--candidateMatchIdx;
}
}
(*nbMatches)++;
} else {
matches[*nbMatches].len = candidateMatchLength;
matches[*nbMatches].off = candidateOffCode;
(*nbMatches)++;
}
}
}
/* ZSTD_opt_processLdm():
* Wrapper function to update ldm seq store and call ldm functions as necessary.