core: Handle empty JPEGTables tags (fix #116)

core/src/backend/render.rs

@@ -10,7 +10,7 @@ pub trait RenderBackend {
         &mut self,
         id: swf::CharacterId,
         data: &[u8],
-        jpeg_tables: &[u8],
+        jpeg_tables: Option<&[u8]>,
     ) -> BitmapInfo;
     fn register_bitmap_jpeg_2(&mut self, id: swf::CharacterId, data: &[u8]) -> BitmapInfo;
     fn register_bitmap_jpeg_3(
@@ -80,7 +80,7 @@ impl RenderBackend for NullRenderer {
         &mut self,
         _id: swf::CharacterId,
         _data: &[u8],
-        _jpeg_tables: &[u8],
+        _jpeg_tables: Option<&[u8]>,
     ) -> BitmapInfo {
         BitmapInfo {
             handle: BitmapHandle(0),
@@ -133,6 +133,28 @@ pub fn glue_swf_jpeg_to_tables(jpeg_tables: &[u8], jpeg_data: &[u8]) -> Vec<u8>
     full_jpeg
 }
 
+/// Glues the JPEG encoding tables from a JPEGTables SWF tag to the JPEG data
+/// in a DefineBits tag, producing complete JPEG data suitable for a decoder.
+pub fn glue_tables_to_jpeg<'a>(
+    jpeg_data: &'a [u8],
+    jpeg_tables: Option<&'a [u8]>,
+) -> std::borrow::Cow<'a, [u8]> {
+    if let Some(jpeg_tables) = jpeg_tables {
+        if jpeg_tables.len() >= 2 {
+            let mut full_jpeg = Vec::with_capacity(jpeg_tables.len() + jpeg_data.len());
+            full_jpeg.extend_from_slice(&jpeg_tables[..jpeg_tables.len() - 2]);
+            if jpeg_data.len() >= 2 {
+                full_jpeg.extend_from_slice(&jpeg_data[2..]);
+            }
+
+            return std::borrow::Cow::from(full_jpeg);
+        }
+    }
+
+    // No JPEG tables or not enough data; return JPEG data as is
+    std::borrow::Cow::Borrowed(jpeg_data)
+}
+
 /// Removes potential invalid JPEG data from SWF DefineBitsJPEG tags.
 ///
 /// SWF19 p.138:

core/src/display_object/movie_clip.rs

@@ -886,11 +886,10 @@ impl<'gc, 'a> MovieClip<'gc> {
             .get_mut()
             .take(data_len as u64)
             .read_to_end(&mut jpeg_data)?;
-        let bitmap_info = context.renderer.register_bitmap_jpeg(
-            id,
-            &jpeg_data,
-            context.library.jpeg_tables().unwrap(),
-        );
+        let bitmap_info =
+            context
+                .renderer
+                .register_bitmap_jpeg(id, &jpeg_data, context.library.jpeg_tables());
         let bitmap = crate::display_object::Bitmap::new(
             context,
             id,

core/src/library.rs

@@ -86,8 +86,19 @@ impl<'gc> Library<'gc> {
     }
 
     pub fn set_jpeg_tables(&mut self, data: Vec<u8>) {
-        let data = crate::backend::render::remove_invalid_jpeg_data(&data[..]).to_vec();
-        self.jpeg_tables = Some(data);
+        if self.jpeg_tables.is_some() {
+            // SWF spec says there should only be one JPEGTables tag.
+            // TODO: What is the behavior when there are multiples?
+            log::warn!("SWF contains multiple JPEGTables tags");
+            return;
+        }
+        // Some SWFs have a JPEGTables tag with 0 length; ignore these.
+        // (Does this happen when there is only a single DefineBits tag?)
+        self.jpeg_tables = if data.is_empty() {
+            None
+        } else {
+            Some(crate::backend::render::remove_invalid_jpeg_data(&data[..]).to_vec())
+        }
     }
 
     pub fn jpeg_tables(&self) -> Option<&[u8]> {

desktop/src/render.rs

@@ -542,16 +542,10 @@ impl RenderBackend for GliumRenderBackend {
         &mut self,
         id: swf::CharacterId,
         data: &[u8],
-        jpeg_tables: &[u8],
+        jpeg_tables: Option<&[u8]>,
     ) -> BitmapInfo {
-        if !jpeg_tables.is_empty() {
-            let mut full_jpeg = jpeg_tables[..jpeg_tables.len() - 2].to_vec();
-            full_jpeg.extend_from_slice(&data[2..]);
-
-            self.register_bitmap_jpeg_2(id, &full_jpeg[..])
-        } else {
-            self.register_bitmap_jpeg_2(id, &data[..])
-        }
+        let data = ruffle_core::backend::render::glue_tables_to_jpeg(data, jpeg_tables);
+        self.register_bitmap_jpeg_2(id, &data[..])
     }
 
     fn register_bitmap_jpeg_2(&mut self, id: swf::CharacterId, data: &[u8]) -> BitmapInfo {

web/src/render.rs

@@ -360,12 +360,10 @@ impl RenderBackend for WebCanvasRenderBackend {
         &mut self,
         id: CharacterId,
         data: &[u8],
-        jpeg_tables: &[u8],
+        jpeg_tables: Option<&[u8]>,
     ) -> BitmapInfo {
-        let mut full_jpeg = jpeg_tables[..jpeg_tables.len() - 2].to_vec();
-        full_jpeg.extend_from_slice(&data[2..]);
-
-        self.register_bitmap_jpeg_2(id, &full_jpeg[..])
+        let data = ruffle_core::backend::render::glue_tables_to_jpeg(data, jpeg_tables);
+        self.register_bitmap_jpeg_2(id, &data[..])
     }
 
     fn register_bitmap_jpeg_2(&mut self, id: CharacterId, data: &[u8]) -> BitmapInfo {