From: senhuang42 <senhuang96@fb.com>
Date: Tue, 6 Oct 2020 17:44:44 +0000 (-0400)
Subject: Replace offCode of largest match if ldm's offCode is superior
X-Git-Tag: v1.4.7~57^2~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0c515590d81efd2f6655a0f0c992ab33ff76bcdd;p=thirdparty%2Fzstd.git

Replace offCode of largest match if ldm's offCode is superior
---

diff --git a/lib/compress/zstd_opt.c b/lib/compress/zstd_opt.c
index 0baba0b18..80b8e28c9 100644
--- a/lib/compress/zstd_opt.c
+++ b/lib/compress/zstd_opt.c
@@ -874,8 +874,11 @@ static void ZSTD_optLdm_maybeAddMatch(ZSTD_match_t* matches, U32* nbMatches,
         matches[*nbMatches].off = candidateOffCode;
         (*nbMatches)++;
     } else if ((candidateMatchLength >= matches[*nbMatches-1].len) && *nbMatches < ZSTD_OPT_NUM) {
-        /* 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) {
+        if (candidateMatchLength == matches[*nbMatches-1].len) {
+            /* No need to insert match with same matchLength. At most, replace offCode if it is smaller. */
+            if (candidateOffCode < matches[*nbMatches-1].off) {
+                matches[*nbMatches-1].off = candidateOffCode;
+            }
             return;
         }
         matches[*nbMatches].len = candidateMatchLength;