Mypal/image/decoders/nsIconDecoder.cpp

/* -*- Mode: C++; tab-width: 8; 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/. */

#include "nsIconDecoder.h"
#include "RasterImage.h"
#include "SurfacePipeFactory.h"

using namespace mozilla::gfx;

namespace mozilla {
namespace image {

static const uint32_t ICON_HEADER_SIZE = 2;

nsIconDecoder::nsIconDecoder(RasterImage* aImage)
 : Decoder(aImage)
 , mLexer(Transition::To(State::HEADER, ICON_HEADER_SIZE),
          Transition::TerminateSuccess())
 , mBytesPerRow()   // set by ReadHeader()
{
  // Nothing to do
}

nsIconDecoder::~nsIconDecoder()
{ }

LexerResult
nsIconDecoder::DoDecode(SourceBufferIterator& aIterator, IResumable* aOnResume)
{
  MOZ_ASSERT(!HasError(), "Shouldn't call DoDecode after error!");

  return mLexer.Lex(aIterator, aOnResume,
                    [=](State aState, const char* aData, size_t aLength) {
    switch (aState) {
      case State::HEADER:
        return ReadHeader(aData);
      case State::ROW_OF_PIXELS:
        return ReadRowOfPixels(aData, aLength);
      case State::FINISH:
        return Finish();
      default:
        MOZ_CRASH("Unknown State");
    }
  });
}

LexerTransition<nsIconDecoder::State>
nsIconDecoder::ReadHeader(const char* aData)
{
  // Grab the width and height.
  uint8_t width  = uint8_t(aData[0]);
  uint8_t height = uint8_t(aData[1]);

  // The input is 32bpp, so we expect 4 bytes of data per pixel.
  mBytesPerRow = width * 4;

  // Post our size to the superclass.
  PostSize(width, height);

  // Icons have alpha.
  PostHasTransparency();

  // If we're doing a metadata decode, we're done.
  if (IsMetadataDecode()) {
    return Transition::TerminateSuccess();
  }

  MOZ_ASSERT(!mImageData, "Already have a buffer allocated?");
  Maybe<SurfacePipe> pipe =
    SurfacePipeFactory::CreateSurfacePipe(this, Size(), OutputSize(),
                                          FullFrame(), SurfaceFormat::B8G8R8A8,
                                          /* aAnimParams */ Nothing(),
                                          SurfacePipeFlags());
  if (!pipe) {
    return Transition::TerminateFailure();
  }

  mPipe = Move(*pipe);

  MOZ_ASSERT(mImageData, "Should have a buffer now");

  return Transition::To(State::ROW_OF_PIXELS, mBytesPerRow);
}

LexerTransition<nsIconDecoder::State>
nsIconDecoder::ReadRowOfPixels(const char* aData, size_t aLength)
{
  MOZ_ASSERT(aLength % 4 == 0, "Rows should contain a multiple of four bytes");

  auto result = mPipe.WritePixels<uint32_t>([&]() -> NextPixel<uint32_t> {
    if (aLength == 0) {
      return AsVariant(WriteState::NEED_MORE_DATA);  // Done with this row.
    }

    uint32_t pixel;
    memcpy(&pixel, aData, 4);
    aData += 4;
    aLength -= 4;

    return AsVariant(pixel);
  });

  MOZ_ASSERT(result != WriteState::FAILURE);

  Maybe<SurfaceInvalidRect> invalidRect = mPipe.TakeInvalidRect();
  if (invalidRect) {
    PostInvalidation(invalidRect->mInputSpaceRect,
                     Some(invalidRect->mOutputSpaceRect));
  }

  return result == WriteState::FINISHED
       ? Transition::To(State::FINISH, 0)
       : Transition::To(State::ROW_OF_PIXELS, mBytesPerRow);
}

LexerTransition<nsIconDecoder::State>
nsIconDecoder::Finish()
{
  PostFrameStop();
  PostDecodeDone();

  return Transition::TerminateSuccess();
}

} // namespace image
} // namespace mozilla