From: Mika Lindqvist <postmaster@raasu.org>
Date: Sun, 19 Jun 2016 12:21:46 +0000 (+0300)
Subject: Don't update prev if old head is same as new.
X-Git-Tag: 1.9.9-b1~770^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F72%2Fhead;p=thirdparty%2Fzlib-ng.git

Don't update prev if old head is same as new.
---

diff --git a/arch/x86/insert_string_sse.c b/arch/x86/insert_string_sse.c
index 90c619a8..6d4ddaea 100644
--- a/arch/x86/insert_string_sse.c
+++ b/arch/x86/insert_string_sse.c
@@ -39,9 +39,12 @@ Pos insert_string_sse(deflate_state *const s, const Pos str, unsigned int count)
         );
 #endif
 
-        ret = s->prev[(str+idx) & s->w_mask] = s->head[h & s->hash_mask];
-        s->head[h & s->hash_mask] = str+idx;
+        if (s->head[h & s->hash_mask] != str+idx) {
+            s->prev[(str+idx) & s->w_mask] = s->head[h & s->hash_mask];
+            s->head[h & s->hash_mask] = str+idx;
+        }
     }
+    ret = s->prev[(str+count-1) & s->w_mask];
     return ret;
 }
 #endif
diff --git a/deflate_p.h b/deflate_p.h
index 9b45b091..4b8282d4 100644
--- a/deflate_p.h
+++ b/deflate_p.h
@@ -42,9 +42,12 @@ local inline Pos insert_string_c(deflate_state *const s, const Pos str, uInt cou
 
     for (idx = 0; idx < count; idx++) {
         UPDATE_HASH(s, s->ins_h, str+idx);
-        ret = s->prev[(str+idx) & s->w_mask] = s->head[s->ins_h];
-        s->head[s->ins_h] = str+idx;
+        if (s->head[s->ins_h] != str+idx) {
+            s->prev[(str+idx) & s->w_mask] = s->head[s->ins_h];
+            s->head[s->ins_h] = str+idx;
+        }
     }
+    ret = s->prev[(str+count-1) & s->w_mask];
     return ret;
 }