From fa7d7934f608edcb9ca7c36f0a74256a4fd7aaa8 Mon Sep 17 00:00:00 2001
From: Glenn Randers-Pehrson <glennrp at users.sourceforge.net>
Date: Wed, 5 Oct 2011 21:09:22 -0500
Subject: [PATCH] [libpng15] Replaced a short but frequently-used memcpy() in
 png_combine_row()

with a loop.
---
 ANNOUNCE   |  5 +++--
 CHANGES    |  3 ++-
 pngrutil.c | 16 +++++++++++++---
 3 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/ANNOUNCE b/ANNOUNCE
index a07147bf1..569ded81e 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.5.6beta05 - October 5, 2011
+Libpng 1.5.6beta05 - October 6, 2011
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -55,7 +55,8 @@ Version 1.5.6beta03 [September 28, 2011]
 Version 1.5.6beta04 [October 5, 2011]
   Fixed typo in Makefile.in and Makefile.am ("-M Wl" should be "-M -Wl")."
 
-Version 1.5.6beta05 [October 5, 2011]
+Version 1.5.6beta05 [October 6, 2011]
+  Replaced a short but frequently-used memcpy() in png_combine_row() to a loop.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net:
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 367b3e568..7f44659df 100644
--- a/CHANGES
+++ b/CHANGES
@@ -3616,7 +3616,8 @@ Version 1.5.6beta03 [September 28, 2011]
 Version 1.5.6beta04 [October 5, 2011]
   Fixed typo in Makefile.in and Makefile.am ("-M Wl" should be "-M -Wl")."
 
-Version 1.5.6beta05 [October 5, 2011]
+Version 1.5.6beta05 [October 6, 2011]
+  Replaced a short but frequently-used memcpy() in png_combine_row() to a loop.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/pngrutil.c b/pngrutil.c
index 0de1fa942..d8ab11776 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -2994,11 +2994,21 @@ png_combine_row(png_structp png_ptr, png_bytep row, int mask)
             {
                if (m & mask)
                {
-                  png_memcpy(dp, sp, pixel_bytes);
+                  /* Prior to libpng-1.5.6 we used memcpy(), but limited
+                   * experiments show that this simple loop can be
+                   * significantly faster.
+                   */
+                  int j;
+
+                  for (j = pixel_bytes; j; --j)
+                     *(dp++) = *(sp++);
                }
 
-               sp += pixel_bytes;
-               dp += pixel_bytes;
+               else
+               {
+                 sp += pixel_bytes;
+                 dp += pixel_bytes;
+               }
 
                if (m == 1)
                   m = 0x80;