gecko-dev/image/decoders/nsIconDecoder.cpp
Nicholas Nethercote ce10603db1 Bug 1210291 - Streamline StreamingLexer's handling of terminal states. r=seth.
This patch introduces TerminalState and changes LexerTransition::mNextState to
be a Variant<State, TerminalState>. This means that SUCCESS and FAILURE no
longer need to be part of State.

Some things to note:

- This simplifies the handling of Lex()'s return value, which is nice.

- The patch splits Terminate() into TerminateSuccess() and TerminateFailure().

- |const State& aNextState| wouldn't work for the first arg to
  LexerTransition's ctor due to errors in Variant construction that I didn't
  understand. I had to change it to |State aNextState|.

--HG--
extra : rebase_source : f405a67fdf0f1bb712409eafecb21ac9b59d6db0
2015-10-28 01:30:20 -07:00

142 lines
3.8 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 "nsIInputStream.h"
#include "nspr.h"
#include "nsRect.h"
#include "nsError.h"
#include "RasterImage.h"
#include <algorithm>
using namespace mozilla::gfx;
using std::min;
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))
, mWidth() // set by ReadHeader()
, mHeight() // set by ReadHeader()
, mBytesPerRow() // set by ReadHeader()
, mCurrentRow(0)
{
// Nothing to do
}
nsIconDecoder::~nsIconDecoder()
{ }
void
nsIconDecoder::WriteInternal(const char* aBuffer, uint32_t aCount)
{
MOZ_ASSERT(!HasError(), "Shouldn't call WriteInternal after error!");
MOZ_ASSERT(aBuffer);
MOZ_ASSERT(aCount > 0);
Maybe<TerminalState> terminalState =
mLexer.Lex(aBuffer, aCount, [=](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");
}
});
if (terminalState == Some(TerminalState::FAILURE)) {
PostDataError();
}
}
LexerTransition<nsIconDecoder::State>
nsIconDecoder::ReadHeader(const char* aData)
{
// Grab the width and height.
mWidth = uint8_t(aData[0]);
mHeight = uint8_t(aData[1]);
// The input is 32bpp, so we expect 4 bytes of data per pixel.
mBytesPerRow = mWidth * 4;
// Post our size to the superclass.
PostSize(mWidth, mHeight);
// 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?");
IntSize targetSize = mDownscaler ? mDownscaler->TargetSize() : GetSize();
nsresult rv = AllocateFrame(0, targetSize,
IntRect(IntPoint(), targetSize),
gfx::SurfaceFormat::B8G8R8A8);
if (NS_FAILED(rv)) {
return Transition::TerminateFailure();
}
MOZ_ASSERT(mImageData, "Should have a buffer now");
if (mDownscaler) {
nsresult rv = mDownscaler->BeginFrame(GetSize(), Nothing(),
mImageData, /* aHasAlpha = */ true);
if (NS_FAILED(rv)) {
return Transition::TerminateFailure();
}
}
return Transition::To(State::ROW_OF_PIXELS, mBytesPerRow);
}
LexerTransition<nsIconDecoder::State>
nsIconDecoder::ReadRowOfPixels(const char* aData, size_t aLength)
{
if (mDownscaler) {
memcpy(mDownscaler->RowBuffer(), aData, mBytesPerRow);
mDownscaler->CommitRow();
if (mDownscaler->HasInvalidation()) {
DownscalerInvalidRect invalidRect = mDownscaler->TakeInvalidRect();
PostInvalidation(invalidRect.mOriginalSizeRect,
Some(invalidRect.mTargetSizeRect));
}
} else {
memcpy(mImageData + mCurrentRow * mBytesPerRow, aData, mBytesPerRow);
PostInvalidation(IntRect(0, mCurrentRow, mWidth, 1));
}
mCurrentRow++;
return (mCurrentRow < mHeight)
? Transition::To(State::ROW_OF_PIXELS, mBytesPerRow)
: Transition::To(State::FINISH, 0);
}
LexerTransition<nsIconDecoder::State>
nsIconDecoder::Finish()
{
PostFrameStop();
PostDecodeDone();
return Transition::TerminateSuccess();
}
} // namespace image
} // namespace mozilla