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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef mozilla_image_decoders_nsGIFDecoder2_h
#define mozilla_image_decoders_nsGIFDecoder2_h
#include "Decoder.h"
#include "GIF2.h"
#include "StreamingLexer.h"
#include "SurfacePipe.h"
namespace mozilla {
namespace image {
class RasterImage;
//////////////////////////////////////////////////////////////////////
// nsGIFDecoder2 Definition
class nsGIFDecoder2 : public Decoder
{
public:
~nsGIFDecoder2();
protected:
LexerResult DoDecode(SourceBufferIterator& aIterator,
IResumable* aOnResume) override;
nsresult FinishInternal() override;
Maybe<Telemetry::ID> SpeedHistogram() const override;
private:
friend class DecoderFactory;
// Decoders should only be instantiated via DecoderFactory.
explicit nsGIFDecoder2(RasterImage* aImage);
/// Called when we begin decoding the image.
void BeginGIF();
/**
* Called when we begin decoding a frame.
*
* @param aFrameRect The region of the image that contains data. The region
* outside this rect is transparent.
* @param aDepth The palette depth of this frame.
* @param aIsInterlaced If true, this frame is an interlaced frame.
*/
nsresult BeginImageFrame(const gfx::IntRect& aFrameRect,
uint16_t aDepth,
bool aIsInterlaced);
/// Called when we finish decoding a frame.
void EndImageFrame();
/// Called when we finish decoding the entire image.
void FlushImageData();
/// Transforms a palette index into a pixel.
template <typename PixelSize> PixelSize
ColormapIndexToPixel(uint8_t aIndex);
/// A generator function that performs LZW decompression and yields pixels.
template <typename PixelSize> NextPixel<PixelSize>
YieldPixel(const uint8_t* aData, size_t aLength, size_t* aBytesReadOut);
/// Checks if we have transparency, either because the header indicates that
/// there's alpha, or because the frame rect doesn't cover the entire image.
bool CheckForTransparency(const gfx::IntRect& aFrameRect);
// @return the clear code used for LZW decompression.
int ClearCode() const { return 1 << mGIFStruct.datasize; }
enum class State
{
FAILURE,
SUCCESS,
GIF_HEADER,
SCREEN_DESCRIPTOR,
GLOBAL_COLOR_TABLE,
FINISHED_GLOBAL_COLOR_TABLE,
BLOCK_HEADER,
EXTENSION_HEADER,
GRAPHIC_CONTROL_EXTENSION,
APPLICATION_IDENTIFIER,
NETSCAPE_EXTENSION_SUB_BLOCK,
NETSCAPE_EXTENSION_DATA,
IMAGE_DESCRIPTOR,
FINISH_IMAGE_DESCRIPTOR,
LOCAL_COLOR_TABLE,
FINISHED_LOCAL_COLOR_TABLE,
IMAGE_DATA_BLOCK,
IMAGE_DATA_SUB_BLOCK,
LZW_DATA,
SKIP_LZW_DATA,
FINISHED_LZW_DATA,
SKIP_SUB_BLOCKS,
SKIP_DATA_THEN_SKIP_SUB_BLOCKS,
FINISHED_SKIPPING_DATA
};
LexerTransition<State> ReadGIFHeader(const char* aData);
LexerTransition<State> ReadScreenDescriptor(const char* aData);
LexerTransition<State> ReadGlobalColorTable(const char* aData, size_t aLength);
LexerTransition<State> FinishedGlobalColorTable();
LexerTransition<State> ReadBlockHeader(const char* aData);
LexerTransition<State> ReadExtensionHeader(const char* aData);
LexerTransition<State> ReadGraphicControlExtension(const char* aData);
LexerTransition<State> ReadApplicationIdentifier(const char* aData);
LexerTransition<State> ReadNetscapeExtensionSubBlock(const char* aData);
LexerTransition<State> ReadNetscapeExtensionData(const char* aData);
LexerTransition<State> ReadImageDescriptor(const char* aData);
LexerTransition<State> FinishImageDescriptor(const char* aData);
LexerTransition<State> ReadLocalColorTable(const char* aData, size_t aLength);
LexerTransition<State> FinishedLocalColorTable();
LexerTransition<State> ReadImageDataBlock(const char* aData);
LexerTransition<State> ReadImageDataSubBlock(const char* aData);
LexerTransition<State> ReadLZWData(const char* aData, size_t aLength);
LexerTransition<State> SkipSubBlocks(const char* aData);
// The StreamingLexer used to manage input. The initial size of the buffer is
// chosen as a little larger than the maximum size of any fixed-length data we
// have to read for a state. We read variable-length data in unbuffered mode
// so the buffer shouldn't have to be resized during decoding.
StreamingLexer<State, 16> mLexer;
uint32_t mOldColor; // The old value of the transparent pixel
// The frame number of the currently-decoding frame when we're in the middle
// of decoding it, and -1 otherwise.
int32_t mCurrentFrameIndex;
// When we're reading in the global or local color table, this records our
// current position - i.e., the offset into which the next byte should be
// written.
size_t mColorTablePos;
uint8_t mColorMask; // Apply this to the pixel to keep within colormap
bool mGIFOpen;
bool mSawTransparency;
gif_struct mGIFStruct;
SurfacePipe mPipe; /// The SurfacePipe used to write to the output surface.
};
} // namespace image
} // namespace mozilla
#endif // mozilla_image_decoders_nsGIFDecoder2_h
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