Eliminate copies of encoded image data

third_party/WebKit/Source/platform/image-decoders/FastSharedBufferReader.h

 /*
  * Copyright (C) 2015 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 14 matching lines @@
  * 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.
  */
 
 #ifndef FastSharedBufferReader_h
 #define FastSharedBufferReader_h
 
 #include "platform/PlatformExport.h"
-#include "platform/SharedBuffer.h"
+#include "platform/image-decoders/SegmentReader.h"
 #include "wtf/Allocator.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 // This class is used by image decoders to avoid memory consolidation and
 // therefore minimizes the cost of memory copying when the decoders
 // repeatedly read from a buffer that is continually growing due to network
 // traffic.
 class PLATFORM_EXPORT FastSharedBufferReader final {
     DISALLOW_NEW();
     WTF_MAKE_NONCOPYABLE(FastSharedBufferReader);
 public:
-    FastSharedBufferReader(PassRefPtr<SharedBuffer> data);
+    FastSharedBufferReader(PassRefPtr<SegmentReader> data);
 
-    void setData(PassRefPtr<SharedBuffer>);
+    void setData(PassRefPtr<SegmentReader>);
 
     // Returns a consecutive buffer that carries the data starting
     // at |dataPosition| with |length| bytes.
     // This method returns a pointer to a memory segment stored in
     // |m_data| if such a consecutive buffer can be found.
     // Otherwise copies into |buffer| and returns it.
     // Caller must ensure there are enough bytes in |m_data| and |buffer|.
     const char* getConsecutiveData(size_t dataPosition, size_t length, char* buffer) const;
 
-    // Wraps SharedBuffer::getSomeData().
+    // Wraps SegmentReader::getSomeData().
     size_t getSomeData(const char*& someData, size_t dataPosition) const;
 
     // Returns a byte at |dataPosition|.
     // Caller must ensure there are enough bytes in |m_data|.
     inline char getOneByte(size_t dataPosition) const
     {
         return *getConsecutiveData(dataPosition, 1, 0);
     }
 
     size_t size() const
     {
         return m_data->size();
     }
 
     // This class caches the last access for faster subsequent reads. This
-    // method clears that cache in case the SharedBuffer has been modified
+    // method clears that cache in case the SegmentReader has been modified

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

This should still say SharedBuffer

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

Done.

     // (i.e. with mergeSegmentsIntoBuffer).
     void clearCache();
 
 private:
     void getSomeDataInternal(unsigned dataPosition) const;
 
-    RefPtr<SharedBuffer> m_data;
+    RefPtr<SegmentReader> m_data;
 
     // Caches the last segment of |m_data| accessed, since subsequent reads are
     // likely to re-access it.
     mutable const char* m_segment;
     mutable size_t m_segmentLength;
 
     // Data position in |m_data| pointed to by |m_segment|.
     mutable size_t m_dataPosition;
 };
 
 } // namespace blink
 
 #endif