Move gif image decoder to SkCodec

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

+// Copyright (c) 2017 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.
+
+#ifndef SegmentStream_h
+#define SegmentStream_h
+
+#include <algorithm>
+#include "platform/image-decoders/SegmentReader.h"

[scroggo_chromium, 2017/08/15 15:19:44]

In [1] I suggested changing this to a forward declare (which requires not
inlining getLength). Thoughts?


[1]
https://codereview.chromium.org/2565323003/diff/3080001/third_party/WebKit/So...

[cblume, 2017/08/15 18:03:33]

Oh sorry. I thought you had suggested forward declaring SegmentStream (in
GIFImageDecoder.h) rather than SegmentReader (here). I've now done both. :)

+#include "platform/wtf/RefPtr.h"
+#include "third_party/skia/include/core/SkStream.h"
+
+namespace blink {
+
+class PLATFORM_EXPORT SegmentStream : public SkStream {
+ public:
+  SegmentStream();
+  SegmentStream(SegmentStream&& rhs);
+  ~SegmentStream() override;
+
+  SegmentStream& operator=(SegmentStream&& rhs);
+
+  void SetReader(WTF::RefPtr<SegmentReader>);
+  // If a buffer has shrunk beyond the point we have read, it has been cleared.
+  // This allows clients to be aware of when data suddenly disappears.
+  bool IsCleared() const { return is_cleared_; }
+
+  // From SkStream:
+  size_t read(void* buffer, size_t) override;
+  size_t peek(void* buffer, size_t) const override;
+  bool isAtEnd() const override { return has_read_all_contents_; }
+  bool rewind() override;
+  bool hasPosition() const override { return true; }
+  size_t getPosition() const override { return position_; }
+  bool seek(size_t position) override;
+  bool move(long offset) override;
+  bool hasLength() const override { return true; }
+  size_t getLength() const override {
+    if (reader_)
+      return reader_->size();
+
+    return 0;
+  }
+
+ private:
+  void SetPositionState(size_t new_position);
+
+  WTF::RefPtr<SegmentReader> reader_;
+  size_t position_ = 0;
+  // |has_read_all_contents_| indicates if we have read all the contents of the
+  // buffer.
+  bool has_read_all_contents_ = true;
+  // |is_cleared_| tracks if we have shrunk the buffer beyond the point we have
+  // read. Clients of this class rely on data not disappearing, so we need to
+  // handle the case when it does.
+  bool is_cleared_ = true;
+};
+
+}  // namespace blink
+
+#endif