Eliminate copies of encoded image data

third_party/WebKit/Source/platform/image-decoders/DataSegmentReader.cpp

+// Copyright 2016 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.
+
+#include "platform/image-decoders/SegmentReader.h"
+
+#include "third_party/skia/include/core/SkData.h"
+#include "wtf/Noncopyable.h"
+#include "wtf/PassRefPtr.h"
+#include "wtf/RefPtr.h"
+
+namespace blink {
+
+// Interface for ImageDecoder to read an SkData.
+class DataSegmentReader final : public SegmentReader {
+    WTF_MAKE_NONCOPYABLE(DataSegmentReader);
+public:
+    DataSegmentReader(PassRefPtr<SkData>);
+    size_t size() const override;
+    size_t getSomeData(const char*& data, size_t position) const override;
+    PassRefPtr<SkData> getAsSkData() const override;
+private:
+    RefPtr<SkData> m_data;
+};
+
+PassRefPtr<SegmentReader> SegmentReader::createFromSkData(PassRefPtr<SkData> data)
+{
+    return adoptRef(new DataSegmentReader(data));
+}
+
+DataSegmentReader::DataSegmentReader(PassRefPtr<SkData> data)
+    : m_data(data) {}
+
+size_t DataSegmentReader::size() const
+{
+    return m_data->size();
+}
+
+size_t DataSegmentReader::getSomeData(const char*& data, size_t position) const
+{
+    if (position >= m_data->size())
+        return 0;
+
+    data = reinterpret_cast<const char*>(m_data->bytes() + position);
+    return m_data->size() - position;
+}
+
+PassRefPtr<SkData> DataSegmentReader::getAsSkData() const
+{
+    return m_data.get();
+}
+
+} // namespace blink
+