[gdk-pixbuf] GIF: assert and assume that the module callbacks are non-NULL

[Emmanuele Bassi <ebassi src gnome org>]

commit c972f7fba5f5842bf8013d28f6e9b88dabbf430d
Author: Federico Mena Quintero <federico gnome org>
Date:   Wed Nov 29 07:06:06 2017 -0600

    GIF: assert and assume that the module callbacks are non-NULL

 gdk-pixbuf/io-gif.c | 97 ++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 66 insertions(+), 31 deletions(-)
---
diff --git a/gdk-pixbuf/io-gif.c b/gdk-pixbuf/io-gif.c
index 3fba50e11..8ba67b9cb 100644
--- a/gdk-pixbuf/io-gif.c
+++ b/gdk-pixbuf/io-gif.c
@@ -502,12 +502,12 @@ gif_get_lzw (GifContext *context)
                 context->animation->frames = g_list_append (context->animation->frames, context->frame);
 
                /* Notify when have first frame */
-               if (context->animation->frames->next == NULL && context->prepare_func != NULL) {
+               if (context->animation->frames->next == NULL) {
                        GdkPixbuf *pixbuf = gdk_pixbuf_animation_get_static_image (GDK_PIXBUF_ANIMATION 
(context->animation));
                        if (pixbuf != NULL)
                                (* context->prepare_func) (pixbuf,
-                                                          GDK_PIXBUF_ANIMATION (context->animation),
-                                                          context->user_data);
+                                                           GDK_PIXBUF_ANIMATION (context->animation),
+                                                           context->user_data);
                }
         }
 
@@ -518,12 +518,12 @@ gif_get_lzw (GifContext *context)
                retval = get_data_block (context, (unsigned char *) context->block_buf, &empty_block);
 
                /* Notify frame update */
-               if ((retval != 0 || empty_block) && context->animation->frames->next == NULL && 
context->update_func != NULL) {
+               if ((retval != 0 || empty_block) && context->animation->frames->next == NULL) {
                        GdkPixbuf *pixbuf = gdk_pixbuf_animation_get_static_image (GDK_PIXBUF_ANIMATION 
(context->animation));
                        if (pixbuf)
                                (* context->update_func) (pixbuf,
-                                                         0, 0, context->frame->width, context->frame->height,
-                                                         context->user_data);
+                                                          0, 0, context->frame->width, 
context->frame->height,
+                                                          context->user_data);
                }
 
                if (retval != 0)
@@ -574,6 +574,7 @@ gif_init (GifContext *context)
 {
        unsigned char buf[16];
        char version[4];
+        gint width, height;
 
        if (!gif_read (context, buf, 6)) {
                /* Unable to read magic number,
@@ -631,21 +632,17 @@ gif_init (GifContext *context)
         context->animation->width = context->width;
         context->animation->height = context->height;
 
-        if (context->size_func) {
-                gint width, height;
+        width = context->width;
+        height = context->height;
 
-                width = context->width;
-                height = context->height;
+        (*context->size_func) (&width, &height, context->user_data);
 
-                (*context->size_func) (&width, &height, context->user_data);
-
-                if (width == 0 || height == 0) {
-                        g_set_error_literal (context->error,
-                                             GDK_PIXBUF_ERROR,
-                                             GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
-                                             _("Resulting GIF image has zero size"));
-                        return -2;
-                }
+        if (width == 0 || height == 0) {
+                g_set_error_literal (context->error,
+                                     GDK_PIXBUF_ERROR,
+                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
+                                     _("Resulting GIF image has zero size"));
+                return -2;
         }
 
        if (context->has_global_cmap) {
@@ -834,10 +831,17 @@ gif_main_loop (GifContext *context)
 }
 
 static GifContext *
-new_context (void)
+new_context (GdkPixbufModuleSizeFunc size_func,
+             GdkPixbufModulePreparedFunc prepare_func,
+             GdkPixbufModuleUpdatedFunc update_func,
+             gpointer user_data)
 {
        GifContext *context;
 
+        g_assert (size_func != NULL);
+        g_assert (prepare_func != NULL);
+        g_assert (update_func != NULL);
+
        context = g_try_malloc (sizeof (GifContext));
         if (context == NULL)
                 return NULL;
@@ -848,10 +852,10 @@ new_context (void)
        context->frame = NULL;
        context->file = NULL;
        context->state = GIF_START;
-       context->size_func = NULL;
-       context->prepare_func = NULL;
-       context->update_func = NULL;
-       context->user_data = NULL;
+       context->size_func = size_func;
+       context->prepare_func = prepare_func;
+       context->update_func = update_func;
+       context->user_data = user_data;
        context->buf = NULL;
        context->amount_needed = 13;
        context->buf = g_new (guchar, context->amount_needed);
@@ -864,6 +868,37 @@ new_context (void)
 
        return context;
 }
+
+static void
+noop_size_notify (gint     *width,
+                 gint     *height,
+                 gpointer  data)
+{
+}
+
+static void
+noop_prepared_notify (GdkPixbuf *pixbuf,
+                      GdkPixbufAnimation *anim,
+                      gpointer user_data)
+{
+}
+
+static void
+noop_updated_notify (GdkPixbuf *pixbuf,
+                    int        x,
+                    int        y,
+                    int        width,
+                    int        height,
+                    gpointer   user_data)
+{
+}
+
+static GifContext *
+new_context_without_callbacks (void)
+{
+        return new_context (noop_size_notify, noop_prepared_notify, noop_updated_notify, NULL);
+}
+
 /* Shared library entry point */
 static GdkPixbuf *
 gdk_pixbuf__gif_image_load (FILE *file, GError **error)
@@ -874,7 +909,7 @@ gdk_pixbuf__gif_image_load (FILE *file, GError **error)
 
        g_return_val_if_fail (file != NULL, NULL);
 
-       context = new_context ();
+       context = new_context_without_callbacks ();
 
         if (context == NULL) {
                 g_set_error_literal (error,
@@ -923,10 +958,14 @@ gdk_pixbuf__gif_image_begin_load (GdkPixbufModuleSizeFunc size_func,
 {
        GifContext *context;
 
+        g_assert (size_func != NULL);
+        g_assert (prepare_func != NULL);
+        g_assert (update_func != NULL);
+
 #ifdef IO_GIFDEBUG
        count = 0;
 #endif
-       context = new_context ();
+       context = new_context (size_func, prepare_func, update_func, user_data);
 
         if (context == NULL) {
                 g_set_error_literal (error,
@@ -937,10 +976,6 @@ gdk_pixbuf__gif_image_begin_load (GdkPixbufModuleSizeFunc size_func,
         }
         
         context->error = error;
-       context->size_func = size_func;
-       context->prepare_func = prepare_func;
-       context->update_func = update_func;
-       context->user_data = user_data;
 
        return (gpointer) context;
 }
@@ -1049,7 +1084,7 @@ gdk_pixbuf__gif_image_load_animation (FILE *file,
 
        g_return_val_if_fail (file != NULL, NULL);
 
-       context = new_context ();
+       context = new_context_without_callbacks ();
 
         if (context == NULL) {
                 g_set_error_literal (error,