Eliminate copies of encoded image data

third_party/WebKit/Source/web/ImageDecodeBench.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifdef WTF
 
 Provides a minimal wrapping of the Blink image decoders. Used to perform
 a non-threaded, memory-to-memory image decode using micro second accuracy
 clocks to measure image decode time. Optionally applies color correction
 during image decoding on supported platforms (default off). Usage:
 
   % ninja -C /out/Release image_decode_bench &&
      ./out/Release/image_decode_bench file [iterations]
 
 FIXME: Consider adding md5 checksum support to WTF. Use it to compute the
 decoded image frame md5 and output that value.
 
 FIXME: Consider integrating this tool in Chrome telemetry for realz, using
 the image corpii used to assess Blink image decode performance. Refer to
 http://crbug.com/398235#c103 and http://crbug.com/258324#c5
 
 #endif
 
 #include "platform/SharedBuffer.h"
 #include "platform/image-decoders/ImageDecoder.h"
+#include "platform/image-decoders/SharedBufferSegmentReader.h"
 #include "platform/testing/TestingPlatformSupport.h"
 #include "public/platform/Platform.h"
 #include "public/web/WebKit.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassRefPtr.h"
 
 #if defined(_WIN32)
 #if defined(WIN32_LEAN_AND_MEAN)
 #error Fix: WIN32_LEAN_AND_MEAN disables timeBeginPeriod/TimeEndPeriod.
 #endif
@@ skipping 223 matching lines @@
         fprintf(stderr, "Error reading file %s\n", fileName);
         exit(2);
     }
 
     fclose(fp);
     return SharedBuffer::create(buffer.get(), fileSize);
 }
 
 bool decodeImageData(SharedBuffer* data, bool colorCorrection, size_t packetSize)
 {
-    OwnPtr<ImageDecoder> decoder = ImageDecoder::create(*data,
+    RefPtr<SharedBufferSegmentReader> segmentReader = adoptRef(new SharedBufferSegmentReader(data));
+    OwnPtr<ImageDecoder> decoder = ImageDecoder::create(*segmentReader.get(),
         ImageDecoder::AlphaPremultiplied, colorCorrection ?
             ImageDecoder::GammaAndColorProfileApplied : ImageDecoder::GammaAndColorProfileIgnored);
 
     if (!packetSize) {
         bool allDataReceived = true;
-        decoder->setData(data, allDataReceived);
+        decoder->setData(segmentReader.get(), allDataReceived);
 
         int frameCount = decoder->frameCount();
         for (int i = 0; i < frameCount; ++i) {
             if (!decoder->frameBufferAtIndex(i))
                 return false;
         }
 
         return !decoder->failed();
     }
 
     RefPtr<SharedBuffer> packetData = SharedBuffer::create();
+    segmentReader = adoptRef(new SharedBufferSegmentReader(packetData));
     unsigned position = 0;
     while (true) {
         const char* packet;
         unsigned length = data->getSomeData(packet, position);
 
         length = std::min(static_cast<size_t>(length), packetSize);
         packetData->append(packet, length);
         position += length;
 
         bool allDataReceived = position == data->size();
-        decoder->setData(packetData.get(), allDataReceived);
+        decoder->setData(segmentReader.get(), allDataReceived);
 
         int frameCount = decoder->frameCount();
         for (int i = 0; i < frameCount; ++i) {
             if (!decoder->frameBufferAtIndex(i))
                 break;
         }
 
         if (allDataReceived || decoder->failed())
             break;
     }
@@ skipping 92 matching lines @@
             exit(3);
         }
     }
 
     // Results to stdout.
 
     double averageTime = totalTime / static_cast<double>(iterations);
     printf("%f %f\n", totalTime, averageTime);
     return 0;
 }