krak/zstd
krak/zstd
1
0
Fork 0
mirror of https://github.com/facebook/zstd.git synced 2025-03-07 01:10:04 +02:00
Code Issues Releases 1 Activity

Write Back Advanced Hash in Long Matches as Well (+Ratio)

Browse Source 
Since we're now hashing the position ahead even if we find a long match and
don't search that next position, we can write it back into the hashtable even
in long matches. This seems to cost us no speed, and improves compression
ratio slightly!
This commit is contained in:
W. Felix Handte 2021-09-08 12:45:42 -04:00
parent 39f2491bfc
commit 2ddef7c872
1 changed files with 6 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
lib/compress/zstd_double_fast.c
View File

@ -204,6 +204,12 @@ _search_next_long:
while (((ip>anchor) & (matchs0>prefixLowest)) && (ip[-1] == matchs0[-1])) { ip--; matchs0--; mLength++; } /* catch up */
}
/* fall-through */
_match_found: /* requires ip, offset, mLength */
offset_2 = offset_1;
offset_1 = offset;
if (step < 4) {
/* It is unsafe to write this value back to the hashtable when ip1 is
* greater than or equal to the new ip we will have after we're done
@ -215,12 +221,6 @@ _search_next_long:
hashLong[hl1] = (U32)(ip1 - base);
}
/* fall-through */
_match_found: /* requires ip, offset, mLength */
offset_2 = offset_1;
offset_1 = offset;
ZSTD_storeSeq(seqStore, (size_t)(ip-anchor), anchor, iend, offset + ZSTD_REP_MOVE, mLength-MINMATCH);
_match_stored: