Eliminate copies of encoded image data

third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp

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 #include "platform/graphics/DeferredImageDecoder.h"
 
 #include "platform/RuntimeEnabledFeatures.h"
+#include "platform/SharedBuffer.h"
 #include "platform/graphics/DecodingImageGenerator.h"
 #include "platform/graphics/FrameData.h"
 #include "platform/graphics/ImageDecodingStore.h"
 #include "platform/graphics/ImageFrameGenerator.h"
+#include "platform/image-decoders/ROBufferSegmentReader.h"
+#include "platform/image-decoders/SharedBufferSegmentReader.h"
+#include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkImage.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace blink {
 
 bool DeferredImageDecoder::s_enabled = true;
 
 PassOwnPtr<DeferredImageDecoder> DeferredImageDecoder::create(const SharedBuffer& data, ImageDecoder::AlphaOption alphaOption, ImageDecoder::GammaAndColorProfileOption colorOptions)
 {
-    OwnPtr<ImageDecoder> actualDecoder = ImageDecoder::create(data, alphaOption, colorOptions);
+    // FIXME: This const_cast is necessary because the SharedBufferSegmentReader expects a non-const, but
+    // it does not modify it.

[f(malita), 2016/03/23 16:41:57]

Since SharedBufferSegmentReader only calls const SharedBuffer methods, can it be
updated to take/store a const SharedBuffer (and then get rid of this cast)?

[scroggo_chromium, 2016/03/24 13:59:44]

I don't think so. ref() and deref() are not marked const, but it's kind of silly
that this even needs a SegmentReader, when it could easily use a SharedBuffer
directly. Updated so this is unnecessary.

+    RefPtr<SegmentReader> segmentReader = adoptRef(new SharedBufferSegmentReader(const_cast<SharedBuffer*>(&data)));
+    OwnPtr<ImageDecoder> actualDecoder = ImageDecoder::create(*segmentReader.get(), alphaOption, colorOptions);
 
     if (!actualDecoder)
         return nullptr;
 
     return adoptPtr(new DeferredImageDecoder(actualDecoder.release()));
 }
 
 PassOwnPtr<DeferredImageDecoder> DeferredImageDecoder::createForTesting(PassOwnPtr<ImageDecoder> actualDecoder)
 {
     return adoptPtr(new DeferredImageDecoder(std::move(actualDecoder)));
 }
 
 DeferredImageDecoder::DeferredImageDecoder(PassOwnPtr<ImageDecoder> actualDecoder)
     : m_allDataReceived(false)
-    , m_lastDataSize(0)
     , m_actualDecoder(std::move(actualDecoder))
     , m_repetitionCount(cAnimationNone)
     , m_hasColorProfile(false)
     , m_canYUVDecode(false)
 {
 }
 
 DeferredImageDecoder::~DeferredImageDecoder()
 {
 }
@@ skipping 36 matching lines @@
     ImageFrame* frame = m_actualDecoder->frameBufferAtIndex(index);
     if (!frame || frame->status() == ImageFrame::FrameEmpty)
         return nullptr;
 
     return adoptRef(SkImage::NewFromBitmap(frame->bitmap()));
 }
 
 void DeferredImageDecoder::setData(SharedBuffer& data, bool allDataReceived)
 {
     if (m_actualDecoder) {
-        m_data = RefPtr<SharedBuffer>(data);
-        m_lastDataSize = data.size();
+        RefPtr<SegmentReader> segmentReader = adoptRef(new SharedBufferSegmentReader(RefPtr<SharedBuffer>(data)));

[Peter Kasting, 2016/03/23 02:42:58]

Nit: Move down one line

[scroggo_chromium, 2016/03/24 13:59:44]

Done.

         m_allDataReceived = allDataReceived;
-        m_actualDecoder->setData(&data, allDataReceived);
+        m_actualDecoder->setData(segmentReader.get(), allDataReceived);

[Peter Kasting, 2016/03/23 02:42:58]

This pattern (create a local SharedBufferSegmentReader, pass to setData())
happens so many places in this CL that I think it may be worth adding a wrapper
function to ImageDecoder that takes a SharedBuffer directly.

[scroggo_chromium, 2016/03/24 13:59:44]

Agreed. Done.

         prepareLazyDecodedFrames();
     }
 
-    if (m_frameGenerator)
-        m_frameGenerator->setData(&data, allDataReceived);
+    if (m_frameGenerator) {
+        if (!m_rwBuffer) {

[Peter Kasting, 2016/03/23 02:42:58]

Nit: No {} (anywhere we have a one-line body)

[scroggo_chromium, 2016/03/24 13:59:44]

Done.

+            m_rwBuffer = adoptPtr(new SkRWBuffer(data.size()));
+        }
+
+        const char* segment = 0;
+        while (size_t length = data.getSomeData(segment, m_rwBuffer->size())) {

[scroggo_chromium, 2016/03/22 20:18:41]

This copy is analogous to the code in ThreadSafeDataTransport's setData (which
has been removed).

+            m_rwBuffer->append(segment, length);
+        }
+    }
 }
 
 bool DeferredImageDecoder::isSizeAvailable()
 {
     // m_actualDecoder is 0 only if image decoding is deferred and that means
     // the image header decoded successfully and the size is available.
     return m_actualDecoder ? m_actualDecoder->isSizeAvailable() : true;
 }
 
 bool DeferredImageDecoder::hasColorProfile() const
@@ skipping 87 matching lines @@
     if (m_frameGenerator)
         return;
 
     m_size = m_actualDecoder->size();
     m_filenameExtension = m_actualDecoder->filenameExtension();
     // JPEG images support YUV decoding: other decoders do not, WEBP could in future.
     m_canYUVDecode = RuntimeEnabledFeatures::decodeToYUVEnabled() && (m_filenameExtension == "jpg");
     m_hasColorProfile = m_actualDecoder->hasColorProfile();
 
     const bool isSingleFrame = m_actualDecoder->repetitionCount() == cAnimationNone || (m_allDataReceived && m_actualDecoder->frameCount() == 1u);
-    m_frameGenerator = ImageFrameGenerator::create(SkISize::Make(m_actualDecoder->decodedSize().width(), m_actualDecoder->decodedSize().height()), m_data, m_allDataReceived, !isSingleFrame);
+    m_frameGenerator = ImageFrameGenerator::create(SkISize::Make(m_actualDecoder->decodedSize().width(), m_actualDecoder->decodedSize().height()),

[Peter Kasting, 2016/03/23 02:42:58]

Nit: Either put everything on one line, or linebreak in such a way that the args
start at the same horizontal position each line.

[scroggo_chromium, 2016/03/24 13:59:44]

I created a temporary variable, as is done with isSingleFrame, which I think
makes this more readable. (Blink's style guide does not mention anything about
lining up parameters, and I think I tried that, but got a presubmit error. I
think it suggested lining them all up 4 spaces from the first line.)

+        !isSingleFrame);
 }
 
 void DeferredImageDecoder::prepareLazyDecodedFrames()
 {
     if (!s_enabled
         || !m_actualDecoder
         || !m_actualDecoder->isSizeAvailable()
         || m_actualDecoder->filenameExtension() == "ico")
         return;
 
@@ skipping 15 matching lines @@
 
     // The last lazy decoded frame created from previous call might be
     // incomplete so update its state.
     if (previousSize) {
         const size_t lastFrame = previousSize - 1;
         m_frameData[lastFrame].m_isComplete = m_actualDecoder->frameIsCompleteAtIndex(lastFrame);
     }
 
     if (m_allDataReceived) {
         m_repetitionCount = m_actualDecoder->repetitionCount();
         m_actualDecoder.clear();

[scroggo_chromium, 2016/03/22 20:18:42]

We hang on to the SkRWBuffer here, unlike the old code and its SharedBuffer,
since we may get more calls to createFrameAtIndex, which will take a snapshot
from the SkRWBuffer.

[Peter Kasting, 2016/03/23 02:42:58]

Might want to write a comment about that.

[scroggo_chromium, 2016/03/24 13:59:45]

Done.

-        m_data = nullptr;
     }
 }
 
 inline SkImageInfo imageInfoFrom(const SkISize& decodedSize, bool knownToBeOpaque)
 {
     return SkImageInfo::MakeN32(decodedSize.width(), decodedSize.height(), knownToBeOpaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType);
 }
 
 PassRefPtr<SkImage> DeferredImageDecoder::createFrameImageAtIndex(size_t index, bool knownToBeOpaque) const
 {
     const SkISize& decodedSize = m_frameGenerator->getFullSize();
     ASSERT(decodedSize.width() > 0);
     ASSERT(decodedSize.height() > 0);
 
-    DecodingImageGenerator* generator = new DecodingImageGenerator(m_frameGenerator, imageInfoFrom(decodedSize, knownToBeOpaque), index);
+    skia::RefPtr<SkROBuffer> roBuffer = skia::AdoptRef(m_rwBuffer->newRBufferSnapshot());

[scroggo_chromium, 2016/03/22 20:18:42]

Some of the Blink code that uses a Skia object wraps it in a skia::RefPtr, and
some uses a RefPtr. I'm not sure which is right (or if we should be using an
sk_sp, which did not exist when I started writing this code). Preferences?

[Peter Kasting, 2016/03/23 02:42:58]

Use skia::RefPtr for now, I think.

[f(malita), 2016/03/23 16:41:58]

skia::RefPtr is only used in Chromium code AFAIK.  In Blink we stick to native
RefPtr/PassRefptr/adoptRef which are compatible with SkRefCnt-derived objects.

My preference would be RefPtr<SkROBuffer> ... = adoptRef(...);

[scroggo_chromium, 2016/03/24 13:59:44]

Yes, it does appear skia::RefPtr is only used in Chromium. Done.

+    RefPtr<SegmentReader> segmentReader = adoptRef(new ROBufferSegmentReader(roBuffer));
+    DecodingImageGenerator* generator = new DecodingImageGenerator(m_frameGenerator, imageInfoFrom(decodedSize, knownToBeOpaque), segmentReader, m_allDataReceived, index);
     RefPtr<SkImage> image = adoptRef(SkImage::NewFromGenerator(generator)); // SkImage takes ownership of the generator.
     if (!image)
         return nullptr;
 
     generator->setGenerationId(image->uniqueID());
     generator->setCanYUVDecode(m_canYUVDecode);
 
     return image.release();
 }
 
 bool DeferredImageDecoder::hotSpot(IntPoint& hotSpot) const
 {
     // TODO: Implement.
     return m_actualDecoder ? m_actualDecoder->hotSpot(hotSpot) : false;
 }
 
 } // namespace blink