[gdk-pixbuf] jpeg: Fix loading truncated incremental inputs

[Bastien Nocera <hadess src gnome org>]

commit b99e04f116972d2ee355fb129238cc574bd58dd3
Author: Bastien Nocera <hadess hadess net>
Date:   Tue Dec 5 06:39:45 2017 +0100

    jpeg: Fix loading truncated incremental inputs
    
    When loading incremental inputs through a GdkPixbufLoader, we didn't
    have any code replicating the stdio_fill_input_buffer() hack to finish
    up a file.
    
    Adding those markers makes libjpeg think that the file was at least
    closed properly, and will attempt decoding.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=753605

 gdk-pixbuf/io-jpeg.c |   21 +++++++++++++++++++--
 1 files changed, 19 insertions(+), 2 deletions(-)
---
diff --git a/gdk-pixbuf/io-jpeg.c b/gdk-pixbuf/io-jpeg.c
index 1e7fcd0..1cd3d30 100644
--- a/gdk-pixbuf/io-jpeg.c
+++ b/gdk-pixbuf/io-jpeg.c
@@ -100,7 +100,8 @@ static gboolean gdk_pixbuf__jpeg_image_stop_load (gpointer context, GError **err
 static gboolean gdk_pixbuf__jpeg_image_load_increment(gpointer context,
                                                       const guchar *buf, guint size,
                                                       GError **error);
-
+static gboolean gdk_pixbuf__jpeg_image_load_lines (JpegProgContext  *context,
+                                                   GError          **error);
 
 static void
 fatal_error_handler (j_common_ptr cinfo)
@@ -848,7 +849,23 @@ gdk_pixbuf__jpeg_image_stop_load (gpointer data, GError **error)
        g_return_val_if_fail (context != NULL, TRUE);
 
        cinfo = &context->cinfo;
-       
+
+       /* Try to finish loading truncated files */
+       if (cinfo->output_scanline < cinfo->output_height) {
+               my_src_ptr src = (my_src_ptr) cinfo->src;
+
+               /* But only if there's enough buffer space left */
+               if (src->skip_next < sizeof(src->buffer) - 2) {
+                       /* Insert a fake EOI marker */
+                       src->buffer[src->skip_next] = (JOCTET) 0xFF;
+                       src->buffer[src->skip_next + 1] = (JOCTET) JPEG_EOI;
+                       src->pub.next_input_byte = src->buffer + src->skip_next;
+                       src->pub.bytes_in_buffer = 2;
+
+                       gdk_pixbuf__jpeg_image_load_lines (context, NULL);
+               }
+       }
+
         /* FIXME this thing needs to report errors if
          * we have unused image data
          */