Eliminate copies of encoded image data

third_party/WebKit/Source/platform/image-decoders/webp/WEBPImageDecoder.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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 137 matching lines @@
 }
 
 void WEBPImageDecoder::clearDecoder()
 {
     WebPIDelete(m_decoder);
     m_decoder = 0;
     m_decodedHeight = 0;
     m_frameBackgroundHasAlpha = false;
 }
 
-void WEBPImageDecoder::onSetData(SharedBuffer*)
+void WEBPImageDecoder::onSetData(SegmentReader*)
 {
     m_haveAlreadyParsedThisData = false;
 }
 
 int WEBPImageDecoder::repetitionCount() const
 {
     return failed() ? cAnimationLoopOnce : m_repetitionCount;
 }
 
 bool WEBPImageDecoder::frameIsCompleteAtIndex(size_t index) const
@@ skipping 19 matching lines @@
     if (m_haveAlreadyParsedThisData)
         return true;
 
     m_haveAlreadyParsedThisData = true;
 
     const unsigned webpHeaderSize = 30;
     if (m_data->size() < webpHeaderSize)
         return false; // Await VP8X header so WebPDemuxPartial succeeds.
 
     WebPDemuxDelete(m_demux);
-    WebPData inputData = { reinterpret_cast<const uint8_t*>(m_data->data()), m_data->size() };
+    m_encodedData = m_data->getAsSkData();

[Peter Kasting, 2016/03/25 06:24:37]

We never reset this anywhere; won't this mean we now hang onto the last data we
looked at even after decoding has finished (succeeded or failed)?

[scroggo, 2016/03/25 15:49:53]

That looks correct. I've updated the code to clear m_encodedData any time we
clear m_demux. Will add urvang@ to look over changes here.

+    WebPData inputData = { reinterpret_cast<const uint8_t*>(m_encodedData->data()), m_encodedData->size() };
     m_demux = WebPDemuxPartial(&inputData, &m_demuxState);
     if (!m_demux || (isAllDataReceived() && m_demuxState != WEBP_DEMUX_DONE))
         return setFailed();
 
     ASSERT(m_demuxState > WEBP_DEMUX_PARSING_HEADER);
     if (!WebPDemuxGetI(m_demux, WEBP_FF_FRAME_COUNT))
         return false; // Wait until the encoded image frame data arrives.
 
     if (!isDecodedSizeAvailable()) {
         int width = WebPDemuxGetI(m_demux, WEBP_FF_CANVAS_WIDTH);
@@ skipping 291 matching lines @@
             return false;
         }
         // FALLTHROUGH
     default:
         clear();
         return setFailed();
     }
 }
 
 } // namespace blink