Bug 399925 - "GIF decoder needs to allow its data to be discarded" [p=alfredkayser@gmail.com (Alfred Kayser) / joe@drew.ca (Joe Drew [JOEDREW!]) r=stuart sr=tor a=blocking1.9+]

modules/libpr0n/decoders/gif/nsGIFDecoder2.cpp

@@ -142,8 +142,18 @@ NS_IMETHODIMP nsGIFDecoder2::Init(imgILoad *aLoad)
 {
   mObserver = do_QueryInterface(aLoad);
 
+  /* The image container may already exist if it is reloading itself from us.
+   */
+  aLoad->GetImage(getter_AddRefs(mImageContainer));
+  if (!mImageContainer) {
     mImageContainer = do_CreateInstance("@mozilla.org/image/container;1");
+    if (!mImageContainer)
+      return NS_ERROR_OUT_OF_MEMORY;
+      
     aLoad->SetImage(mImageContainer);
+    nsresult rv = mImageContainer->SetDiscardable("image/gif");
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+  }
   
   // Start with the version (GIF89a|GIF87a)
   mGIFStruct.state = gif_type;
@@ -174,7 +184,7 @@ NS_IMETHODIMP nsGIFDecoder2::Close()
 /* void flush (); */
 NS_IMETHODIMP nsGIFDecoder2::Flush()
 {
-    return NS_ERROR_NOT_IMPLEMENTED;
+  return NS_OK;
 }
 
 //******************************************************************************
@@ -187,7 +197,7 @@ static NS_METHOD ReadDataOut(nsIInputStream* in,
                              PRUint32 *writeCount)
 {
   nsGIFDecoder2 *decoder = static_cast<nsGIFDecoder2*>(closure);
-  nsresult rv = decoder->ProcessData((unsigned char*)fromRawSegment, count, writeCount);
+  nsresult rv = decoder->ProcessData(fromRawSegment, count, writeCount);
   if (NS_FAILED(rv)) {
     *writeCount = 0;
     return rv;
@@ -236,11 +246,22 @@ nsGIFDecoder2::FlushImageData()
 }
 
 //******************************************************************************
-nsresult nsGIFDecoder2::ProcessData(unsigned char *data, PRUint32 count, PRUint32 *_retval)
+nsresult nsGIFDecoder2::ProcessData(const char *data, PRUint32 count, PRUint32 *_retval)
 {
-  // Push the data to the GIF decoder
+  // We should just disable the 'restore' when AddRestoreData fails, so that we
+  // still load the image...
+  //
+  // Note that this has to be done before we call GifWrite(), because
+  // GifWrite() can call mImageContainer->RestoreDataDone(), which disallows
+  // any further restore data addition.
+  nsresult rv = mImageContainer->AddRestoreData(data, count);
+  if (NS_FAILED(rv)) { 
+    mGIFStruct.state = gif_oom;
+    return rv;
+  }
 
-  nsresult rv = GifWrite(data, count);
+  // Push the data to the GIF decoder
+  rv = GifWrite((const PRUint8*)data, count);
   NS_ENSURE_SUCCESS(rv, rv);
 
   // Flushing is only needed for first frame
@@ -310,6 +331,7 @@ void nsGIFDecoder2::EndGIF()
   
   mImageContainer->SetLoopCount(mGIFStruct.loop_count);
   mImageContainer->DecodingComplete();
+  (void)mImageContainer->RestoreDataDone(); // Discard error code
 
   mGIFOpen = PR_FALSE;
 }

modules/libpr0n/decoders/gif/nsGIFDecoder2.h

@@ -68,7 +68,7 @@ public:
   nsGIFDecoder2();
   ~nsGIFDecoder2();
   
-  nsresult ProcessData(unsigned char *data, PRUint32 count, PRUint32 *_retval);
+  nsresult ProcessData(const char *data, PRUint32 count, PRUint32 *_retval);
 
 private:
   /* These functions will be called when the decoder has a decoded row,