[WIP] Move ImageDecoders to SkCodec

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
- * copyright notice, this list of conditions and the following disclaimer
- * in the documentation and/or other materials provided with the
- * distribution.
- *     * Neither the name of Google Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * 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.
- */
-
-#ifndef FastSharedBufferReader_h
-#define FastSharedBufferReader_h
-
-#include "platform/PlatformExport.h"
-#include "platform/image-decoders/SegmentReader.h"
-#include "platform/wtf/Allocator.h"
-#include "platform/wtf/Noncopyable.h"
-#include "platform/wtf/PassRefPtr.h"
-#include "platform/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<SegmentReader> data);
-
-  void SetData(PassRefPtr<SegmentReader>);
-
-  // Returns a consecutive buffer that carries the data starting
-  // at |data_position| with |length| bytes.
-  // This method returns a pointer to a memory segment stored in
-  // |data_| if such a consecutive buffer can be found.
-  // Otherwise copies into |buffer| and returns it.
-  // Caller must ensure there are enough bytes in |data_| and |buffer|.
-  const char* GetConsecutiveData(size_t data_position,
-                                 size_t length,
-                                 char* buffer) const;
-
-  // Wraps SegmentReader::GetSomeData().
-  size_t GetSomeData(const char*& some_data, size_t data_position) const;
-
-  // Returns a byte at |data_position|.
-  // Caller must ensure there are enough bytes in |data_|.
-  inline char GetOneByte(size_t data_position) const {
-    return *GetConsecutiveData(data_position, 1, 0);
-  }
-
-  size_t size() const { return data_->size(); }
-
-  // This class caches the last access for faster subsequent reads. This
-  // method clears that cache in case the SegmentReader has been modified
-  // (e.g. with MergeSegmentsIntoBuffer on a wrapped SharedBuffer).
-  void ClearCache();
-
- private:
-  void GetSomeDataInternal(size_t data_position) const;
-
-  RefPtr<SegmentReader> data_;
-
-  // Caches the last segment of |data_| accessed, since subsequent reads are
-  // likely to re-access it.
-  mutable const char* segment_;
-  mutable size_t segment_length_;
-
-  // Data position in |data_| pointed to by |segment_|.
-  mutable size_t data_position_;
-};
-
-}  // namespace blink
-
-#endif