buf_copy(): Fail if there's no data to write or nothing to do

[privoxy.git] / deanimate.c

diff --git a/deanimate.c b/deanimate.c
index ae0d96a..b0f3f1f 100644 (file)
--- a/deanimate.c
+++ b/deanimate.c
@@ -7,10 +7,10 @@
  *                  - Deanimation of GIF images
  *
  * Copyright   :  Written by and Copyright (C) 2001 - 2004, 2006 by the
- *                SourceForge Privoxy team. http://www.privoxy.org/
+ *                Privoxy team. https://www.privoxy.org/
  *
  *                Based on the GIF file format specification (see
- *                http://tronche.com/computer-graphics/gif/gif89a.html)
+ *                https://tronche.com/computer-graphics/gif/gif89a.html)
  *                and ideas from the Image::DeAnim Perl module by
  *                Ken MacFarlane, <ksm+cpan@universal.dca.net>
  *
@@ -40,8 +40,8 @@
 #include <string.h>
 #include <fcntl.h>
 
-#include "errlog.h"
 #include "project.h"
+#include "errlog.h"
 #include "deanimate.h"
 #include "miscutil.h"
 
@@ -131,6 +131,14 @@ static int buf_extend(struct binbuffer *buf, size_t length)
  *********************************************************************/
 static int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
 {
+   /*
+    * Sanity check: Make sure the source buffer contains
+    * data and there's work to be done.
+    */
+   if (src->buffer == NULL || src->size == 0 || length == 0)
+   {
+      return 1;
+   }
 
    /*
     * Sanity check: Can't copy more data than we have
@@ -304,8 +312,8 @@ static int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
  *                an (optional) image block and an arbitrary number
  *                of image extension blocks, produce an output GIF with
  *                only one image block that contains the last image
- *                (extenstion) block of the original.
- *                Also strip Comments, Application extenstions, etc.
+ *                (extension) block of the original.
+ *                Also strip Comments, Application extensions, etc.
  *
  * Parameters  :
  *          1  :  src = Pointer to the source binbuffer