Eliminate copies of encoded image data

third_party/WebKit/Source/web/WebImageDecoder.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 13 matching lines @@
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "public/web/WebImageDecoder.h"
 
 #include "platform/SharedBuffer.h"
+#include "platform/image-decoders/SharedBufferSegmentReader.h"
 #include "platform/image-decoders/bmp/BMPImageDecoder.h"
 #include "platform/image-decoders/ico/ICOImageDecoder.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebData.h"
 #include "public/platform/WebImage.h"
 #include "public/platform/WebSize.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/PassRefPtr.h"
 
@@ skipping 14 matching lines @@
         break;
     case TypeICO:
         m_private = new ICOImageDecoder(ImageDecoder::AlphaPremultiplied, ImageDecoder::GammaAndColorProfileApplied, maxDecodedBytes);
         break;
     }
 }
 
 void WebImageDecoder::setData(const WebData& data, bool allDataReceived)
 {
     ASSERT(m_private);
-    m_private->setData(PassRefPtr<SharedBuffer>(data).get(), allDataReceived);
+    RefPtr<SharedBuffer> buffer = PassRefPtr<SharedBuffer>(data).get();

[Peter Kasting, 2016/03/23 02:42:59]

Nit: Can't we just do something like RefPtr<SharedBuffer> buffer(data); ?

[scroggo_chromium, 2016/03/24 13:59:46]

I don't think so. WebData has a "operator PassRefPtr<SharedBuffer>() const" that
allows this conversion. I tried exactly what you proposed, and it did not work,
but I cannot promise that there is not some other incantation that will.

[Peter Kasting, 2016/03/24 22:05:43]

Yeah, I had been hoping the compiler could figure out that there was a RefPtr
constructor taking a PassRefPtr, and then implicitly invoke that operator.  But
if we have to be explicit about it, so be it.

+    RefPtr<SharedBufferSegmentReader> segmentReader = adoptRef(new SharedBufferSegmentReader(buffer.get()));
+    m_private->setData(segmentReader.get(), allDataReceived);
 }
 
 bool WebImageDecoder::isFailed() const
 {
     ASSERT(m_private);
     return m_private->failed();
 }
 
 bool WebImageDecoder::isSizeAvailable() const
 {
@@ skipping 25 matching lines @@
 WebImage WebImageDecoder::getFrameAtIndex(int index = 0) const
 {
     ASSERT(m_private);
     ImageFrame* const frameBuffer = m_private->frameBufferAtIndex(index);
     if (!frameBuffer)
         return WebImage();
     return WebImage(frameBuffer->bitmap());
 }
 
 } // namespace blink