codecparsers: jpeg: fix and optimize scan for next marker code.

Fix scan for next marker code when there is an odd number of filler
(0xff) bytes before the actual marker code. Also optimize the loop
to execute with fewer instructions (~10%).

This fixes parsing for Spectralfan.mov.

diff --git a/gst-libs/gst/codecparsers/gstjpegparser.c b/gst-libs/gst/codecparsers/gstjpegparser.c
index ac1ba9a..30c67f3 100644 (file)
--- a/gst-libs/gst/codecparsers/gstjpegparser.c
+++ b/gst-libs/gst/codecparsers/gstjpegparser.c
@@ -232,17 +232,16 @@ gst_jpeg_scan_for_marker_code (const guint8 * data, gsize size, guint offset)
   guint i;
 
   g_return_val_if_fail (data != NULL, -1);
-  g_return_val_if_fail (size > offset, -1);
 
-  for (i = offset; i < size - 1;) {
-    if (data[i] != 0xff)
-      i++;
-    else {
-      const guint8 v = data[i + 1];
-      if (v >= 0xc0 && v <= 0xfe)
-        return i;
+  i = offset + 1;
+  while (i < size) {
+    const guint8 v = data[i];
+    if (v < 0xc0)
       i += 2;
-    }
+    else if (v < 0xff && data[i - 1] == 0xff)
+      return i - 1;
+    else
+      i++;
   }
   return -1;
 }