Improve GIF decoding performance

Source/core/platform/image-decoders/gif/GIFImageDecoder.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 13 matching lines @@
  */
 
 #ifndef GIFImageDecoder_h
 #define GIFImageDecoder_h
 
 #include "core/platform/image-decoders/ImageDecoder.h"
 #include "wtf/OwnPtr.h"
 
 class GIFImageReader;
 
+typedef Vector<unsigned char> GIFRow;
+
 namespace WebCore {
 
     // This class decodes the GIF image format.
     class GIFImageDecoder : public ImageDecoder {
     public:
         GIFImageDecoder(ImageSource::AlphaOption, ImageSource::GammaAndColorProfileOption, size_t maxDecodedBytes);
         virtual ~GIFImageDecoder();
 
         enum GIFParseQuery { GIFSizeQuery, GIFFrameCountQuery };
 
         // ImageDecoder
         virtual String filenameExtension() const OVERRIDE { return "gif"; }
         virtual void setData(SharedBuffer* data, bool allDataReceived) OVERRIDE;
         virtual bool isSizeAvailable() OVERRIDE;
         virtual size_t frameCount() OVERRIDE;
         virtual int repetitionCount() const OVERRIDE;
         virtual ImageFrame* frameBufferAtIndex(size_t) OVERRIDE;
         virtual bool frameIsCompleteAtIndex(size_t) const OVERRIDE;
         virtual float frameDurationAtIndex(size_t) const OVERRIDE;
         virtual size_t clearCacheExceptFrame(size_t) OVERRIDE;
         // CAUTION: setFailed() deletes |m_reader|.  Be careful to avoid
         // accessing deleted memory, especially when calling this from inside
         // GIFImageReader!
         virtual bool setFailed() OVERRIDE;
 
         // Callbacks from the GIF reader.
-        bool haveDecodedRow(size_t frameIndex, const Vector<unsigned char>& rowBuffer, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels);
+        bool haveDecodedRow(size_t frameIndex, GIFRow::const_iterator rowBegin, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels);
         bool frameComplete(size_t frameIndex);
 
         // For testing.
         bool parseCompleted() const;
 
     private:
         virtual void clearFrameBuffer(size_t frameIndex) OVERRIDE;
 
         // Parses as much as is needed to answer the query, ignoring bitmap
         // data. If parsing fails, sets the "decode failure" flag.
@@ skipping 10 matching lines @@
         bool initFrameBuffer(size_t frameIndex);
 
         bool m_currentBufferSawAlpha;
         mutable int m_repetitionCount;
         OwnPtr<GIFImageReader> m_reader;
     };
 
 } // namespace WebCore
 
 #endif