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Bug 1315554 - Part 7. Remove unnecessary buffering of BMP header in ICO decoder. r=tnikkel

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This commit is contained in:
Andrew Osmond 2017-07-22 00:14:59 -04:00
parent 88e2751836
commit 1c5f449591
2 changed files with 35 additions and 37 deletions
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69
image/decoders/nsICODecoder.cpp
View File

@ -249,28 +249,38 @@ nsICODecoder::ReadDirEntry(const char* aData)
LexerTransition<ICOState>
nsICODecoder::SniffResource(const char* aData)
{
// Prepare a new iterator for the contained decoder to advance as it wills.
// Cloning at the point ensures it will begin at the resource offset.
mContainedIterator.emplace(mLexer.Clone(*mIterator, mDirEntry.mBytesInRes));
// We have BITMAPINFOSIZE bytes buffered at this point. We know an embedded
// BMP will have at least that many bytes by definition. We can also infer
// that any valid embedded PNG will contain that many bytes as well because:
// BITMAPINFOSIZE
// <
// signature (8 bytes) +
// IHDR (12 bytes header + 13 bytes data)
// IDAT (12 bytes header)
// We use the first PNGSIGNATURESIZE bytes to determine whether this resource
// is a PNG or a BMP.
bool isPNG = !memcmp(aData, nsPNGDecoder::pngSignatureBytes,
PNGSIGNATURESIZE);
if (isPNG) {
if (mDirEntry.mBytesInRes <= PNGSIGNATURESIZE) {
if (mDirEntry.mBytesInRes <= BITMAPINFOSIZE) {
return Transition::TerminateFailure();
}
// Prepare a new iterator for the contained decoder to advance as it wills.
// Cloning at the point ensures it will begin at the resource offset.
SourceBufferIterator containedIterator
= mLexer.Clone(*mIterator, mDirEntry.mBytesInRes);
// Create a PNG decoder which will do the rest of the work for us.
mContainedDecoder =
DecoderFactory::CreateDecoderForICOResource(DecoderType::PNG,
Move(*mContainedIterator),
Move(containedIterator),
WrapNotNull(this),
Some(GetRealSize()));
// Read in the rest of the PNG unbuffered.
size_t toRead = mDirEntry.mBytesInRes - PNGSIGNATURESIZE;
size_t toRead = mDirEntry.mBytesInRes - BITMAPINFOSIZE;
return Transition::ToUnbuffered(ICOState::FINISHED_RESOURCE,
ICOState::READ_RESOURCE,
toRead);
@ -281,12 +291,8 @@ nsICODecoder::SniffResource(const char* aData)
return Transition::TerminateFailure();
}
// Buffer the first part of the bitmap information header.
memcpy(mBIHraw, aData, PNGSIGNATURESIZE);
// Read in the rest of the bitmap information header.
return Transition::To(ICOState::READ_BIH,
BITMAPINFOSIZE - PNGSIGNATURESIZE);
return ReadBIH(aData);
}
}
@ -303,32 +309,35 @@ nsICODecoder::ReadResource()
LexerTransition<ICOState>
nsICODecoder::ReadBIH(const char* aData)
{
// Buffer the rest of the bitmap information header.
memcpy(mBIHraw + PNGSIGNATURESIZE, aData, BITMAPINFOSIZE - PNGSIGNATURESIZE);
// Extract the BPP from the BIH header; it should be trusted over the one
// we have from the ICO header which is usually set to 0.
mBPP = LittleEndian::readUint16(mBIHraw + 14);
mBPP = LittleEndian::readUint16(aData + 14);
// Check to make sure we have valid color settings.
uint16_t numColors = GetNumColors();
if (numColors == uint16_t(-1)) {
return Transition::TerminateFailure();
}
// The color table is present only if BPP is <= 8.
MOZ_ASSERT_IF(mBPP > 8, numColors == 0);
// The ICO format when containing a BMP does not include the 14 byte
// bitmap file header. So we create the BMP decoder via the constructor that
// tells it to skip this, and pass in the required data (dataOffset) that
// would have been present in the header.
uint32_t dataOffset = bmp::FILE_HEADER_LENGTH + BITMAPINFOSIZE;
if (mBPP <= 8) {
// The color table is present only if BPP is <= 8.
uint16_t numColors = GetNumColors();
if (numColors == (uint16_t)-1) {
return Transition::TerminateFailure();
}
dataOffset += 4 * numColors;
}
uint32_t dataOffset = bmp::FILE_HEADER_LENGTH + BITMAPINFOSIZE + 4 * numColors;
// Prepare a new iterator for the contained decoder to advance as it wills.
// Cloning at the point ensures it will begin at the resource offset.
SourceBufferIterator containedIterator
= mLexer.Clone(*mIterator, mDirEntry.mBytesInRes);
// Create a BMP decoder which will do most of the work for us; the exception
// is the AND mask, which isn't present in standalone BMPs.
mContainedDecoder =
DecoderFactory::CreateDecoderForICOResource(DecoderType::BMP,
Move(*mContainedIterator),
Move(containedIterator),
WrapNotNull(this),
Some(GetRealSize()),
Some(dataOffset));
@ -341,12 +350,6 @@ nsICODecoder::ReadBIH(const char* aData)
return Transition::TerminateFailure();
}
// Check to make sure we have valid color settings.
uint16_t numColors = GetNumColors();
if (numColors == uint16_t(-1)) {
return Transition::TerminateFailure();
}
// Do we have an AND mask on this BMP? If so, we need to read it after we read
// the BMP data itself.
uint32_t bmpDataLength = bmpDecoder->GetCompressedImageSize() + 4 * numColors;
@ -562,13 +565,11 @@ nsICODecoder::DoDecode(SourceBufferIterator& aIterator, IResumable* aOnResume)
case ICOState::SKIP_TO_RESOURCE:
return Transition::ContinueUnbuffered(ICOState::SKIP_TO_RESOURCE);
case ICOState::FOUND_RESOURCE:
return Transition::To(ICOState::SNIFF_RESOURCE, PNGSIGNATURESIZE);
return Transition::To(ICOState::SNIFF_RESOURCE, BITMAPINFOSIZE);
case ICOState::SNIFF_RESOURCE:
return SniffResource(aData);
case ICOState::READ_RESOURCE:
return ReadResource();
case ICOState::READ_BIH:
return ReadBIH(aData);
case ICOState::PREPARE_FOR_MASK:
return PrepareForMask();
case ICOState::READ_MASK_ROW:

3
image/decoders/nsICODecoder.h
View File

@ -28,7 +28,6 @@ enum class ICOState
FOUND_RESOURCE,
SNIFF_RESOURCE,
READ_RESOURCE,
READ_BIH,
PREPARE_FOR_MASK,
READ_MASK_ROW,
FINISH_MASK,
@ -101,9 +100,7 @@ private:
StreamingLexer<ICOState, 32> mLexer; // The lexer.
RefPtr<Decoder> mContainedDecoder; // Either a BMP or PNG decoder.
Maybe<SourceBufferIterator> mContainedIterator; // Iterator for the subdecoder.
UniquePtr<uint8_t[]> mMaskBuffer; // A temporary buffer for the alpha mask.
char mBIHraw[bmp::InfoHeaderLength::WIN_ICO]; // The bitmap information header.
IconDirEntry mDirEntry; // The dir entry for the selected resource.
gfx::IntSize mBiggestResourceSize; // Used to select the intrinsic size.
gfx::IntSize mBiggestResourceHotSpot; // Used to select the intrinsic size.