mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-10-13 05:15:45 +00:00
Bug 1382683 - Part 2. Switch nsGIFDecoder2 to write pixels in blocks instead of individually. r=tnikkel
nsGIFDecoder2::YieldPixel is sufficiently complex that the optimizer does not appear to inline it with the rest of the templated methods. As such there is a high cost to calling it. This patch modifies it to yield a requested number of pixels before exiting, allowing us to amortize the cost of calling across a row instead of a pixel. Based on profiling, this will significantly reduce the time require to decode a frame.
This commit is contained in:
Andrew Osmond
parent
5bcb89ae72
commit
cb1d37e391
@ -292,10 +292,12 @@ nsGIFDecoder2::ColormapIndexToPixel<uint8_t>(uint8_t aIndex)
|
||||
}
|
||||
|
||||
template <typename PixelSize>
|
||||
NextPixel<PixelSize>
|
||||
nsGIFDecoder2::YieldPixel(const uint8_t* aData,
|
||||
size_t aLength,
|
||||
size_t* aBytesReadOut)
|
||||
Tuple<int32_t, Maybe<WriteState>>
|
||||
nsGIFDecoder2::YieldPixels(const uint8_t* aData,
|
||||
size_t aLength,
|
||||
size_t* aBytesReadOut,
|
||||
PixelSize* aPixelBlock,
|
||||
int32_t aBlockSize)
|
||||
{
|
||||
MOZ_ASSERT(aData);
|
||||
MOZ_ASSERT(aBytesReadOut);
|
||||
@ -304,108 +306,119 @@ nsGIFDecoder2::YieldPixel(const uint8_t* aData,
|
||||
// Advance to the next byte we should read.
|
||||
const uint8_t* data = aData + *aBytesReadOut;
|
||||
|
||||
// If we don't have any decoded data to yield, try to read some input and
|
||||
// produce some.
|
||||
if (mGIFStruct.stackp == mGIFStruct.stack) {
|
||||
while (mGIFStruct.bits < mGIFStruct.codesize && *aBytesReadOut < aLength) {
|
||||
// Feed the next byte into the decoder's 32-bit input buffer.
|
||||
mGIFStruct.datum += int32_t(*data) << mGIFStruct.bits;
|
||||
mGIFStruct.bits += 8;
|
||||
data += 1;
|
||||
*aBytesReadOut += 1;
|
||||
}
|
||||
|
||||
if (mGIFStruct.bits < mGIFStruct.codesize) {
|
||||
return AsVariant(WriteState::NEED_MORE_DATA);
|
||||
}
|
||||
|
||||
// Get the leading variable-length symbol from the data stream.
|
||||
int code = mGIFStruct.datum & mGIFStruct.codemask;
|
||||
mGIFStruct.datum >>= mGIFStruct.codesize;
|
||||
mGIFStruct.bits -= mGIFStruct.codesize;
|
||||
|
||||
const int clearCode = ClearCode();
|
||||
|
||||
// Reset the dictionary to its original state, if requested
|
||||
if (code == clearCode) {
|
||||
mGIFStruct.codesize = mGIFStruct.datasize + 1;
|
||||
mGIFStruct.codemask = (1 << mGIFStruct.codesize) - 1;
|
||||
mGIFStruct.avail = clearCode + 2;
|
||||
mGIFStruct.oldcode = -1;
|
||||
return AsVariant(WriteState::NEED_MORE_DATA);
|
||||
}
|
||||
|
||||
// Check for explicit end-of-stream code. It should only appear after all
|
||||
// image data, but if that was the case we wouldn't be in this function, so
|
||||
// this is always an error condition.
|
||||
if (code == (clearCode + 1)) {
|
||||
return AsVariant(WriteState::FAILURE);
|
||||
}
|
||||
|
||||
if (mGIFStruct.oldcode == -1) {
|
||||
if (code >= MAX_BITS) {
|
||||
return AsVariant(WriteState::FAILURE); // The code's too big; something's wrong.
|
||||
int32_t written = 0;
|
||||
while (aBlockSize > written) {
|
||||
// If we don't have any decoded data to yield, try to read some input and
|
||||
// produce some.
|
||||
if (mGIFStruct.stackp == mGIFStruct.stack) {
|
||||
while (mGIFStruct.bits < mGIFStruct.codesize && *aBytesReadOut < aLength) {
|
||||
// Feed the next byte into the decoder's 32-bit input buffer.
|
||||
mGIFStruct.datum += int32_t(*data) << mGIFStruct.bits;
|
||||
mGIFStruct.bits += 8;
|
||||
data += 1;
|
||||
*aBytesReadOut += 1;
|
||||
}
|
||||
|
||||
mGIFStruct.firstchar = mGIFStruct.oldcode = code;
|
||||
|
||||
// Yield a pixel at the appropriate index in the colormap.
|
||||
mGIFStruct.pixels_remaining--;
|
||||
return AsVariant(ColormapIndexToPixel<PixelSize>(mGIFStruct.suffix[code]));
|
||||
}
|
||||
|
||||
int incode = code;
|
||||
if (code >= mGIFStruct.avail) {
|
||||
*mGIFStruct.stackp++ = mGIFStruct.firstchar;
|
||||
code = mGIFStruct.oldcode;
|
||||
|
||||
if (mGIFStruct.stackp >= mGIFStruct.stack + MAX_BITS) {
|
||||
return AsVariant(WriteState::FAILURE); // Stack overflow; something's wrong.
|
||||
}
|
||||
}
|
||||
|
||||
while (code >= clearCode) {
|
||||
if ((code >= MAX_BITS) || (code == mGIFStruct.prefix[code])) {
|
||||
return AsVariant(WriteState::FAILURE);
|
||||
if (mGIFStruct.bits < mGIFStruct.codesize) {
|
||||
return MakeTuple(written, Some(WriteState::NEED_MORE_DATA));
|
||||
}
|
||||
|
||||
*mGIFStruct.stackp++ = mGIFStruct.suffix[code];
|
||||
code = mGIFStruct.prefix[code];
|
||||
// Get the leading variable-length symbol from the data stream.
|
||||
int code = mGIFStruct.datum & mGIFStruct.codemask;
|
||||
mGIFStruct.datum >>= mGIFStruct.codesize;
|
||||
mGIFStruct.bits -= mGIFStruct.codesize;
|
||||
|
||||
if (mGIFStruct.stackp >= mGIFStruct.stack + MAX_BITS) {
|
||||
return AsVariant(WriteState::FAILURE); // Stack overflow; something's wrong.
|
||||
const int clearCode = ClearCode();
|
||||
|
||||
// Reset the dictionary to its original state, if requested
|
||||
if (code == clearCode) {
|
||||
mGIFStruct.codesize = mGIFStruct.datasize + 1;
|
||||
mGIFStruct.codemask = (1 << mGIFStruct.codesize) - 1;
|
||||
mGIFStruct.avail = clearCode + 2;
|
||||
mGIFStruct.oldcode = -1;
|
||||
return MakeTuple(written, Some(WriteState::NEED_MORE_DATA));
|
||||
}
|
||||
|
||||
// Check for explicit end-of-stream code. It should only appear after all
|
||||
// image data, but if that was the case we wouldn't be in this function, so
|
||||
// this is always an error condition.
|
||||
if (code == (clearCode + 1)) {
|
||||
return MakeTuple(written, Some(WriteState::FAILURE));
|
||||
}
|
||||
|
||||
if (mGIFStruct.oldcode == -1) {
|
||||
if (code >= MAX_BITS) {
|
||||
// The code's too big; something's wrong.
|
||||
return MakeTuple(written, Some(WriteState::FAILURE));
|
||||
}
|
||||
|
||||
mGIFStruct.firstchar = mGIFStruct.oldcode = code;
|
||||
|
||||
// Yield a pixel at the appropriate index in the colormap.
|
||||
mGIFStruct.pixels_remaining--;
|
||||
aPixelBlock[written++] =
|
||||
ColormapIndexToPixel<PixelSize>(mGIFStruct.suffix[code]);
|
||||
continue;
|
||||
}
|
||||
|
||||
int incode = code;
|
||||
if (code >= mGIFStruct.avail) {
|
||||
*mGIFStruct.stackp++ = mGIFStruct.firstchar;
|
||||
code = mGIFStruct.oldcode;
|
||||
|
||||
if (mGIFStruct.stackp >= mGIFStruct.stack + MAX_BITS) {
|
||||
// Stack overflow; something's wrong.
|
||||
return MakeTuple(written, Some(WriteState::FAILURE));
|
||||
}
|
||||
}
|
||||
|
||||
while (code >= clearCode) {
|
||||
if ((code >= MAX_BITS) || (code == mGIFStruct.prefix[code])) {
|
||||
return MakeTuple(written, Some(WriteState::FAILURE));
|
||||
}
|
||||
|
||||
*mGIFStruct.stackp++ = mGIFStruct.suffix[code];
|
||||
code = mGIFStruct.prefix[code];
|
||||
|
||||
if (mGIFStruct.stackp >= mGIFStruct.stack + MAX_BITS) {
|
||||
// Stack overflow; something's wrong.
|
||||
return MakeTuple(written, Some(WriteState::FAILURE));
|
||||
}
|
||||
}
|
||||
|
||||
*mGIFStruct.stackp++ = mGIFStruct.firstchar = mGIFStruct.suffix[code];
|
||||
|
||||
// Define a new codeword in the dictionary.
|
||||
if (mGIFStruct.avail < 4096) {
|
||||
mGIFStruct.prefix[mGIFStruct.avail] = mGIFStruct.oldcode;
|
||||
mGIFStruct.suffix[mGIFStruct.avail] = mGIFStruct.firstchar;
|
||||
mGIFStruct.avail++;
|
||||
|
||||
// If we've used up all the codewords of a given length increase the
|
||||
// length of codewords by one bit, but don't exceed the specified maximum
|
||||
// codeword size of 12 bits.
|
||||
if (((mGIFStruct.avail & mGIFStruct.codemask) == 0) &&
|
||||
(mGIFStruct.avail < 4096)) {
|
||||
mGIFStruct.codesize++;
|
||||
mGIFStruct.codemask += mGIFStruct.avail;
|
||||
}
|
||||
}
|
||||
|
||||
mGIFStruct.oldcode = incode;
|
||||
}
|
||||
|
||||
*mGIFStruct.stackp++ = mGIFStruct.firstchar = mGIFStruct.suffix[code];
|
||||
|
||||
// Define a new codeword in the dictionary.
|
||||
if (mGIFStruct.avail < 4096) {
|
||||
mGIFStruct.prefix[mGIFStruct.avail] = mGIFStruct.oldcode;
|
||||
mGIFStruct.suffix[mGIFStruct.avail] = mGIFStruct.firstchar;
|
||||
mGIFStruct.avail++;
|
||||
|
||||
// If we've used up all the codewords of a given length increase the
|
||||
// length of codewords by one bit, but don't exceed the specified maximum
|
||||
// codeword size of 12 bits.
|
||||
if (((mGIFStruct.avail & mGIFStruct.codemask) == 0) &&
|
||||
(mGIFStruct.avail < 4096)) {
|
||||
mGIFStruct.codesize++;
|
||||
mGIFStruct.codemask += mGIFStruct.avail;
|
||||
}
|
||||
if (MOZ_UNLIKELY(mGIFStruct.stackp <= mGIFStruct.stack)) {
|
||||
MOZ_ASSERT_UNREACHABLE("No decoded data but we didn't return early?");
|
||||
return MakeTuple(written, Some(WriteState::FAILURE));
|
||||
}
|
||||
|
||||
mGIFStruct.oldcode = incode;
|
||||
// Yield a pixel at the appropriate index in the colormap.
|
||||
mGIFStruct.pixels_remaining--;
|
||||
aPixelBlock[written++]
|
||||
= ColormapIndexToPixel<PixelSize>(*--mGIFStruct.stackp);
|
||||
}
|
||||
|
||||
if (MOZ_UNLIKELY(mGIFStruct.stackp <= mGIFStruct.stack)) {
|
||||
MOZ_ASSERT_UNREACHABLE("No decoded data but we didn't return early?");
|
||||
return AsVariant(WriteState::FAILURE);
|
||||
}
|
||||
|
||||
// Yield a pixel at the appropriate index in the colormap.
|
||||
mGIFStruct.pixels_remaining--;
|
||||
return AsVariant(ColormapIndexToPixel<PixelSize>(*--mGIFStruct.stackp));
|
||||
return MakeTuple(written, Maybe<WriteState>());
|
||||
}
|
||||
|
||||
/// Expand the colormap from RGB to Packed ARGB as needed by Cairo.
|
||||
@ -1032,8 +1045,12 @@ nsGIFDecoder2::ReadLZWData(const char* aData, size_t aLength)
|
||||
size_t bytesRead = 0;
|
||||
|
||||
auto result = mGIFStruct.images_decoded == 0
|
||||
? mPipe.WritePixels<uint32_t>([&]{ return YieldPixel<uint32_t>(data, length, &bytesRead); })
|
||||
: mPipe.WritePixels<uint8_t>([&]{ return YieldPixel<uint8_t>(data, length, &bytesRead); });
|
||||
? mPipe.WritePixelBlocks<uint32_t>([&](uint32_t* aPixelBlock, int32_t aBlockSize) {
|
||||
return YieldPixels<uint32_t>(data, length, &bytesRead, aPixelBlock, aBlockSize);
|
||||
})
|
||||
: mPipe.WritePixelBlocks<uint8_t>([&](uint8_t* aPixelBlock, int32_t aBlockSize) {
|
||||
return YieldPixels<uint8_t>(data, length, &bytesRead, aPixelBlock, aBlockSize);
|
||||
});
|
||||
|
||||
if (MOZ_UNLIKELY(bytesRead > length)) {
|
||||
MOZ_ASSERT_UNREACHABLE("Overread?");
|
||||
|
||||
@ -65,8 +65,12 @@ private:
|
||||
ColormapIndexToPixel(uint8_t aIndex);
|
||||
|
||||
/// A generator function that performs LZW decompression and yields pixels.
|
||||
template <typename PixelSize> NextPixel<PixelSize>
|
||||
YieldPixel(const uint8_t* aData, size_t aLength, size_t* aBytesReadOut);
|
||||
template <typename PixelSize> Tuple<int32_t, Maybe<WriteState>>
|
||||
YieldPixels(const uint8_t* aData,
|
||||
size_t aLength,
|
||||
size_t* aBytesReadOut,
|
||||
PixelSize* aPixelBlock,
|
||||
int32_t aBlockSize);
|
||||
|
||||
/// Checks if we have transparency, either because the header indicates that
|
||||
/// there's alpha, or because the frame rect doesn't cover the entire image.
|
||||
|
||||
Loading…
Reference in New Issue
Block a user