[PPAPI] Implement an IOStreamResource for data transmission between plugin and renderer.

ppapi/shared_impl/io_stream_shared.h

+// Copyright (c) 2014 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 PPAPI_SHARED_IMPL_IO_STREAM_SHARED_H_
+#define PPAPI_SHARED_IMPL_IO_STREAM_SHARED_H_
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/shared_memory.h"
+#include "ppapi/shared_impl/circular_buffer.h"
+#include "ppapi/shared_impl/ppapi_shared_export.h"
+
+namespace ppapi {
+
+class CircularBuffer;
+
+class PPAPI_SHARED_EXPORT IOStreamShared {
+ public:
+  int32_t Write(const void* buffer, uint32_t size);
+
+  int32_t WriteAll(const void* buffer, uint32_t size);
+
+  int32_t Read(void* buffer, uint32_t size);
+
+  int32_t ReadAll(void* buffer, uint32_t size);
+
+  int32_t Lock(void** buffer, uint32_t size);
+
+  int32_t Relock(void* buffer, uint32_t size);
+
+  int32_t Unlock(void* buffer);
+
+  uint32_t remaining() const;
+
+  bool is_input() { return is_input_; }
+
+  const base::SharedMemory* shared_memory() const {
+    return shm_.get();
+  }
+
+ protected:
+  IOStreamShared(bool is_input);
+
+  virtual ~IOStreamShared();
+
+  // Set the underlying shared memory.
+  int32_t SetBuffer(scoped_ptr<base::SharedMemory> shm, uint32_t size);
+
+  // Subclass uses this function to move the limit position of the
+  // |circular_buffer_|.
+  void MoveLimit(uint32_t offset);
+
+  // Subclass may overridden this function to receive notification when
+  // more buffer is available.
+  virtual void OnMoreBufferAvailable();
+
+ private:
+  // Move limit position at the another peer of an IOStream pair.
+  // Subclass should send IPC message to the another peer to move the limit
+  // position.
+  virtual void MovePeerLimit(uint32_t offset) = 0;
+
+  // True if it is an input peer of an IO stream, otherwise it is an output peer
+  // of an IO stream.
+  bool is_input_;
+
+  // Shared memory.
+  scoped_ptr<base::SharedMemory> shm_;
+
+  // A new shared memory will be used to replace the existing |shm_|.
+  scoped_ptr<base::SharedMemory> shm_new_;
+
+  // Circular buffer
+  scoped_ptr<CircularBuffer> circular_buffer_;
+
+  scoped_ptr<CircularBuffer> circular_buffer_new_;
+
+  DISALLOW_COPY_AND_ASSIGN(IOStreamShared);
+};
+
+}  // namespace ppapi
+
+#endif  // PPAPI_SHARED_IMPL_IO_STREAM_SHARED_H_