Move gif image decoder to SkCodec

third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h

 /*
  * Copyright (C) 2006 Apple Computer, 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
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``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 APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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  * 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 GIFImageDecoder_h
 #define GIFImageDecoder_h
 
 #include "platform/image-decoders/ImageDecoder.h"
+#include "third_party/skia/include/codec/SkCodec.h"
+#include "third_party/skia/include/core/SkStream.h"
 #include "wtf/Noncopyable.h"
+#include "wtf/RefPtr.h"
+#include <algorithm>
 #include <memory>
 
-class GIFImageReader;
-
-typedef Vector<unsigned char> GIFRow;
-
 namespace blink {
 
 // This class decodes the GIF image format.
 class PLATFORM_EXPORT GIFImageDecoder final : public ImageDecoder {
   WTF_MAKE_NONCOPYABLE(GIFImageDecoder);
 
  public:
   GIFImageDecoder(AlphaOption, const ColorBehavior&, size_t maxDecodedBytes);
   ~GIFImageDecoder() override;
 
-  enum GIFParseQuery { GIFSizeQuery, GIFFrameCountQuery };
-
   // ImageDecoder:
   String filenameExtension() const override { return "gif"; }
   void onSetData(SegmentReader* data) override;
   int repetitionCount() const override;
   bool frameIsCompleteAtIndex(size_t) const override;
   float frameDurationAtIndex(size_t) const override;
-  // CAUTION: setFailed() deletes |m_reader|.  Be careful to avoid
-  // accessing deleted memory, especially when calling this from inside
-  // GIFImageReader!
-  bool setFailed() override;
-
-  // Callbacks from the GIF reader.
-  bool haveDecodedRow(size_t frameIndex,
-                      GIFRow::const_iterator rowBegin,
-                      size_t width,
-                      size_t rowNumber,
-                      unsigned repeatCount,
-                      bool writeTransparentPixels);
-  bool frameComplete(size_t frameIndex);
-
-  // For testing.
-  bool parseCompleted() const;
 
  private:
   // ImageDecoder:
-  void clearFrameBuffer(size_t frameIndex) override;
-  virtual void decodeSize() { parse(GIFSizeQuery); }
+  void decodeSize() override {}
   size_t decodeFrameCount() override;
   void initializeNewFrame(size_t) override;
   void decode(size_t) override;
-
-  // Parses as much as is needed to answer the query, ignoring bitmap
-  // data. If parsing fails, sets the "decode failure" flag.
-  void parse(GIFParseQuery);
-
-  // Reset the alpha tracker for this frame. Before calling this method, the
-  // caller must verify that the frame exists.
-  void onInitFrameBuffer(size_t) override;
-
   // When the disposal method of the frame is DisposeOverWritePrevious, the
   // next frame will use the previous frame's buffer as its starting state, so
   // we can't take over the data in that case. Before calling this method, the
   // caller must verify that the frame exists.
   bool canReusePreviousFrameBuffer(size_t) const override;
 
-  bool m_currentBufferSawAlpha;
-  mutable int m_repetitionCount;
-  std::unique_ptr<GIFImageReader> m_reader;
+  class SegmentStream : public SkStream {
+   public:
+    SegmentStream() : m_reader(), m_position(0), m_hasReadAllContents(true) {}
+
+    void setReader(SegmentReader* reader, bool allContentsReceived) {
+      m_reader = reader;
+      m_hasReadAllContents = reader->size() == m_position;
+    }
+
+    size_t read(void* dst, size_t len) {
+      len = std::min(len, m_reader->size());
+
+      size_t bytesAdvanced = 0;
+      if (!dst) {  // skipping, not reading
+        bytesAdvanced = len;
+      } else {
+        bytesAdvanced = peek(dst, len);
+      }
+
+      m_position += bytesAdvanced;
+      m_hasReadAllContents = m_position == m_reader->size();
+
+      return bytesAdvanced;
+    }
+
+    size_t peek(void* buffer, size_t size) const override {
+      size = std::min(size, m_reader->size());
+
+      size_t totalBytesPeeked = 0;
+      char* bufferAsCharPtr = reinterpret_cast<char*>(buffer);
+      while (size) {
+        const char* segment = nullptr;
+        size_t bytesPeeked = m_reader->getSomeData(segment, m_position);

[scroggo_chromium, 2017/01/03 22:36:58]

The second time through this loop, we'll be reading from the same position,
since we do not update m_position.

FWIW, I think it would be simpler to implement peek with read, rather than read
with peek, as you've done here. i.e.:

size_t peek(void* buffer, size_t size) const override {
  size_t position = m_position;
  size_t bytesPeeked = read(buffer, size);
  m_position = position;
  return bytesPeeked;
}

[cblume, 2017/01/04 01:30:28]

Fixed. Thank you.
But peek is const and read is not.
read() wants to update m_position.
I could make m_position mutable. But I don't think that is better than read
relying on peek.

+        if (!bytesPeeked) {
+          break;
+        }
+        if (bytesPeeked > size) {
+          bytesPeeked = size;
+        }
+
+        memcpy(bufferAsCharPtr, segment, bytesPeeked);
+        bufferAsCharPtr += bytesPeeked;
+        size -= bytesPeeked;
+        totalBytesPeeked += bytesPeeked;
+      }
+
+      return totalBytesPeeked;
+    }
+
+    bool isAtEnd() const override { return m_hasReadAllContents; }
+
+    bool rewind() override {
+      m_position = 0;
+      return true;
+    }
+
+    bool hasPosition() const override { return false; }
+    size_t getPosition() const override { return m_position; }
+
+    bool seek(size_t position) override {
+      position = std::min(position, m_reader->size());
+      m_position = position;
+
+      return true;
+    }
+
+    bool hasLength() const override { return false; }
+    size_t getLength() const override { return m_reader->size(); }
+
+   private:
+    WTF::RefPtr<SegmentReader> m_reader;
+    size_t m_position;
+    bool m_hasReadAllContents;
+  };
+
+  std::unique_ptr<SkCodec> m_codec;
+  SegmentStream* m_segmentStream;
+  // m_segmentStream is a raw pointer because it passes ownership to
+  // m_codec when m_codec is created. However, we still need the
+  // reference so we can append more data as it arrives.
 };
 
 }  // namespace blink
 
 #endif