Decode GIF image frames on demand.

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

 /* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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@@ skipping 221 matching lines @@
         , m_bytesToConsume(6) // Number of bytes for GIF type, either "GIF87a" or "GIF89a".
         , m_bytesRead(0)
         , m_screenBgcolor(0)
         , m_version(0)
         , m_screenWidth(0)
         , m_screenHeight(0)
         , m_isGlobalColormapDefined(false)
         , m_globalColormapPosition(0)
         , m_globalColormapSize(0)
         , m_loopCount(cLoopCountNotSeen)
-        , m_currentDecodingFrame(0)
+        , m_decodedFramesCount(0)
         , m_parseCompleted(false)
     {
     }
 
     ~GIFImageReader()
     {
     }
 
     void setData(PassRefPtr<WebCore::SharedBuffer> data) { m_data = data; }
-    // FIXME: haltAtFrame should be size_t.
-    bool decode(WebCore::GIFImageDecoder::GIFQuery, unsigned haltAtFrame);
+    bool parse(WebCore::GIFImageDecoder::GIFParseQuery);
+    bool decode(const BitVector& frames);

[Alpha Left Google, 2013/05/18 00:39:35]

Why not just give the index? User of this API (GIFImageDecoder) can call this
multiple times.

[Xianzhu, 2013/05/20 04:30:59]

Done.

 
     size_t imagesCount() const
     {
         if (m_frames.isEmpty())
             return 0;
 
         // This avoids counting an empty frame when the file is truncated right after
         // GIFControlExtension but before GIFImageHeader.
         // FIXME: This extra complexity is not necessary and we should just report m_frames.size().
         return m_frames.last()->isHeaderDefined() ? m_frames.size() : m_frames.size() - 1;
@@ skipping 19 matching lines @@
     }
 
     const GIFFrameContext* frameContext(size_t index) const
     {
         return index < m_frames.size() ? m_frames[index].get() : 0;
     }
 
     bool parseCompleted() const { return m_parseCompleted; }
 
 private:
-    bool parse(size_t dataPosition, size_t len, bool parseSizeOnly);
+    bool parseData(size_t dataPosition, size_t len, WebCore::GIFImageDecoder::GIFParseQuery);
     void setRemainingBytes(size_t);
 
     const unsigned char* data(size_t dataPosition) const
     {
         return reinterpret_cast<const unsigned char*>(m_data->data()) + dataPosition;
     }
 
     void addFrameIfNecessary();
     bool currentFrameIsFirstFrame() const
     {
@@ skipping 11 matching lines @@
     int m_screenBgcolor; // Logical screen background color.
     int m_version; // Either 89 for GIF89 or 87 for GIF87.
     unsigned m_screenWidth; // Logical screen width & height.
     unsigned m_screenHeight;
     bool m_isGlobalColormapDefined;
     size_t m_globalColormapPosition; // (3* MAX_COLORS in size) Default colormap if local not supplied, 3 bytes for each color.
     int m_globalColormapSize; // Size of global colormap array.
     int m_loopCount; // Netscape specific extension block to control the number of animation loops a GIF renders.
     
     Vector<OwnPtr<GIFFrameContext> > m_frames;
-    size_t m_currentDecodingFrame;
+    size_t m_decodedFramesCount;

[Alpha Left Google, 2013/05/18 00:39:35]

I don't think we need this any more. See my comments in GIFImageReader.cpp.

[Xianzhu, 2013/05/20 04:30:59]

Done.

 
     RefPtr<WebCore::SharedBuffer> m_data;
     bool m_parseCompleted;
 };
 
 #endif