[gdk-pixbuf] JPEG: skip bytes during incremental load

[Emmanuele Bassi <ebassi src gnome org>]

commit 35dcd72bbe7a9349861ff14389a38525fe9c949f
Author: Nathan Lee <utasstudent-git1271 yahoo com>
Date:   Sat Feb 15 07:04:46 2020 +0000

    JPEG: skip bytes during incremental load
    
    Previously only skipped bytes at the start of incremental
    loads. During a incremental load, there may be bytes to skip
    between reloads. Previous behavior misread metadata sometimes.
    
    Fixes #70

 gdk-pixbuf/io-jpeg.c | 33 ++++++++++++++++-----------------
 1 file changed, 16 insertions(+), 17 deletions(-)
---
diff --git a/gdk-pixbuf/io-jpeg.c b/gdk-pixbuf/io-jpeg.c
index 7628989d9..ac6adbdf1 100644
--- a/gdk-pixbuf/io-jpeg.c
+++ b/gdk-pixbuf/io-jpeg.c
@@ -970,7 +970,7 @@ gdk_pixbuf__jpeg_image_load_lines (JpegProgContext  *context,
  * buf - new image data
  * size - length of new image data
  *
- * append image data onto inrecrementally built output image
+ * append image data onto incrementally built output image
  */
 static gboolean
 gdk_pixbuf__jpeg_image_load_increment (gpointer data,
@@ -1007,22 +1007,8 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
                goto out;
        }
 
-       /* skip over data if requested, handle unsigned int sizes cleanly */
-       /* only can happen if we've already called jpeg_get_header once   */
-       if (context->src_initialized && src->skip_next) {
-               if (src->skip_next > size) {
-                       src->skip_next -= size;
-                       retval = TRUE;
-                       goto out;
-               } else {
-                       num_left = size - src->skip_next;
-                       bufhd = buf + src->skip_next;
-                       src->skip_next = 0;
-               }
-       } else {
-               num_left = size;
-               bufhd = buf;
-       }
+       num_left = size;
+       bufhd = buf;
 
        if (num_left == 0) {
                retval = TRUE;
@@ -1034,6 +1020,19 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
        spinguard = 0;
        first = TRUE;
        while (TRUE) {
+               /* skip over data if requested, handle unsigned int sizes cleanly */
+               /* only can happen if we've already called jpeg_get_header        */
+               if (context->src_initialized && src->skip_next) {
+                       if (src->skip_next >= num_left) {
+                               src->skip_next -= num_left;
+                               retval = TRUE;
+                               goto out;
+                       } else {
+                               num_left -= src->skip_next;
+                               bufhd += src->skip_next;
+                               src->skip_next = 0;
+                       }
+               }
 
                /* handle any data from caller we haven't processed yet */
                if (num_left > 0) {