image/decoders/nsIconDecoder.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  *
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_image_decoders_nsIconDecoder_h
   8 #define mozilla_image_decoders_nsIconDecoder_h
   9
  10 #include "Decoder.h"
  11 #include "StreamingLexer.h"
  12 #include "SurfacePipe.h"
  13
  14 namespace mozilla {
  15 namespace image {
  16
  17 class RasterImage;
  18
  19 ////////////////////////////////////////////////////////////////////////////////
  20 // The icon decoder is a decoder specifically tailored for loading icons
  21 // from the OS. We've defined our own little format to represent these icons
  22 // and this decoder takes that format and converts it into 24-bit RGB with
  23 // alpha channel support. It was modeled a bit off the PPM decoder.
  24 //
  25 // The format of the incoming data is as follows:
  26 //
  27 // The first two bytes contain the width and the height of the icon.
  28 // The remaining bytes contain the icon data, 4 bytes per pixel, in
  29 // ARGB order (platform endianness, A in highest bits, B in lowest
  30 // bits), row-primary, top-to-bottom, left-to-right, with
  31 // premultiplied alpha.
  32 //
  33 ////////////////////////////////////////////////////////////////////////////////
  34
  35 class nsIconDecoder : public Decoder {
  36  public:
  37   virtual ~nsIconDecoder();
  38
  39   DecoderType GetType() const override { return DecoderType::ICON; }
  40
  41   LexerResult DoDecode(SourceBufferIterator& aIterator,
  42                        IResumable* aOnResume) override;
  43
  44  private:
  45   friend class DecoderFactory;
  46
  47   // Decoders should only be instantiated via DecoderFactory.
  48   explicit nsIconDecoder(RasterImage* aImage);
  49
  50   enum class State { HEADER, ROW_OF_PIXELS, FINISH };
  51
  52   LexerTransition<State> ReadHeader(const char* aData);
  53   LexerTransition<State> ReadRowOfPixels(const char* aData, size_t aLength);
  54   LexerTransition<State> Finish();
  55
  56   StreamingLexer<State> mLexer;
  57   SurfacePipe mPipe;
  58   uint32_t mBytesPerRow;
  59 };
  60
  61 }  // namespace image
  62 }  // namespace mozilla
  63
  64 #endif  // mozilla_image_decoders_nsIconDecoder_h