72 lines
2.2 KiB
C++
72 lines
2.2 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_image_decoders_nsIconDecoder_h
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#define mozilla_image_decoders_nsIconDecoder_h
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#include "Decoder.h"
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#include "StreamingLexer.h"
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#include "nsCOMPtr.h"
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namespace mozilla {
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namespace image {
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class RasterImage;
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////////////////////////////////////////////////////////////////////////////////
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// The icon decoder is a decoder specifically tailored for loading icons
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// from the OS. We've defined our own little format to represent these icons
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// and this decoder takes that format and converts it into 24-bit RGB with
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// alpha channel support. It was modeled a bit off the PPM decoder.
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//
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// Assumptions about the decoder:
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// (1) We receive ALL of the data from the icon channel in one OnDataAvailable
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// call. We don't support multiple ODA calls yet.
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// (2) the format of the incoming data is as follows:
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// The first two bytes contain the width and the height of the icon.
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// The remaining bytes contain the icon data, 4 bytes per pixel, in
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// ARGB order (platform endianness, A in highest bits, B in lowest
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// bits), row-primary, top-to-bottom, left-to-right, with
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// premultiplied alpha.
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//
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//
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////////////////////////////////////////////////////////////////////////////////
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class nsIconDecoder : public Decoder
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{
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public:
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virtual ~nsIconDecoder();
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virtual void WriteInternal(const char* aBuffer, uint32_t aCount) override;
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private:
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friend class DecoderFactory;
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// Decoders should only be instantiated via DecoderFactory.
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explicit nsIconDecoder(RasterImage* aImage);
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enum class State {
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HEADER,
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ROW_OF_PIXELS,
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FINISH
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};
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LexerTransition<State> ReadHeader(const char* aData);
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LexerTransition<State> ReadRowOfPixels(const char* aData, size_t aLength);
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LexerTransition<State> Finish();
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StreamingLexer<State> mLexer;
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uint8_t mWidth;
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uint8_t mHeight;
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uint32_t mBytesPerRow;
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uint32_t mBytesTotal;
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uint32_t mCurrentRow;
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};
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} // namespace image
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} // namespace mozilla
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#endif // mozilla_image_decoders_nsIconDecoder_h
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