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Fix logic in the GIF LOOP-detection parsing

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We align with Blink/Chromium code by:
  - checking for ANIMEXTS1.0 signature too
  - using ByteCount >= 3 instead of requiring ByteCount==3

Change-Id: Idc484ca62878517df3dccb1fdb3bb45104a5e066
see: http://odur.let.rug.nl/kleiweg/gif/netscape.html
This commit is contained in:
skal 2014-06-23 23:26:36 +02:00
parent 5584d9d2fc
commit db8b8b5fc2
1 changed files with 3 additions and 2 deletions
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5
examples/gif2webp.c
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@ -495,11 +495,12 @@ int main(int argc, const char *argv[]) {
}
case APPLICATION_EXT_FUNC_CODE: {
if (data[0] != 11) break; // Chunk is too short
if (!memcmp(data + 1, "NETSCAPE2.0", 11)) {
if (!memcmp(data + 1, "NETSCAPE2.0", 11) ||
!memcmp(data + 1, "ANIMEXTS1.0", 11)) {
// Recognize and parse Netscape2.0 NAB extension for loop count.
if (DGifGetExtensionNext(gif, &data) == GIF_ERROR) goto End;
if (data == NULL) goto End; // Loop count sub-block missing.
if (data[0] != 3 && data[1] != 1) break; // wrong size/marker
if (data[0] < 3 || data[1] != 1) break; // wrong size/marker
anim.loop_count = data[2] | (data[3] << 8);
if (verbose) fprintf(stderr, "Loop count: %d\n", anim.loop_count);
} else { // An extension containing metadata.