nsIconDecoder.h - mozsearch

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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_nsIconDecoder_h

#define mozilla_image_decoders_nsIconDecoder_h

#include "Decoder.h"

#include "StreamingLexer.h"

#include "SurfacePipe.h"

namespace mozilla {

namespace image {

class RasterImage;

////////////////////////////////////////////////////////////////////////////////

// The icon decoder is a decoder specifically tailored for loading icons

// from the OS. We've defined our own little format to represent these icons

// and this decoder takes that format and converts it into 24-bit RGB with

// alpha channel support. It was modeled a bit off the PPM decoder.

//

// The format of the incoming data is as follows:

//

// The first two bytes contain the width and the height of the icon.

// The remaining bytes contain the icon data, 4 bytes per pixel, in

// ARGB order (platform endianness, A in highest bits, B in lowest

// bits), row-primary, top-to-bottom, left-to-right, with

// premultiplied alpha.

//

////////////////////////////////////////////////////////////////////////////////

class nsIconDecoder : public Decoder {

 public:

  virtual ~nsIconDecoder();

  DecoderType GetType() const override { return DecoderType::ICON; }

  LexerResult DoDecode(SourceBufferIterator& aIterator,

                       IResumable* aOnResume) override;

 private:

  friend class DecoderFactory;

  // Decoders should only be instantiated via DecoderFactory.

  explicit nsIconDecoder(RasterImage* aImage);

  enum class State { HEADER, ROW_OF_PIXELS, FINISH };

  LexerTransition<State> ReadHeader(const char* aData);

  LexerTransition<State> ReadRowOfPixels(const char* aData, size_t aLength);

  LexerTransition<State> Finish();

  StreamingLexer<State> mLexer;

  SurfacePipe mPipe;

  uint32_t mBytesPerRow;

};

}  // namespace image

}  // namespace mozilla

#endif  // mozilla_image_decoders_nsIconDecoder_h