[mojo] Use base::Pickle for Message storage.

mojo/public/cpp/bindings/lib/pickle_buffer.h

+// Copyright 2015 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 MOJO_PUBLIC_CPP_BINDINGS_LIB_PICKLE_BUFFER_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_LIB_PICKLE_BUFFER_H_
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/pickle.h"
+#include "mojo/public/cpp/bindings/lib/buffer.h"
+
+namespace mojo {
+namespace internal {
+
+// An implementation of Buffer which uses base::Pickle for its backing. Note
+// that this does not use Pickle's header structure at all, instead storing
+// the complete Message (including header) in the Pickle's payload.
+class PickleBuffer : public Buffer {
+ public:
+  PickleBuffer(size_t num_bytes, bool zero_initialized);
+  ~PickleBuffer() override;
+
+  const void* data() const;
+
+  void* data() {
+    return const_cast<void*>(static_cast<const PickleBuffer*>(this)->data());
+  }
+
+  size_t data_num_bytes() const;
+
+  base::Pickle* pickle() const;
+
+  // Buffer:
+  PickleBuffer* AsPickleBuffer() override;

[yzshen1, 2015/12/16 00:29:28]

nit: It seems nice to put this method and Allocate in the same section because
they are from the same base class.

+
+ private:
+  class Storage;
+
+  // Buffer implementation. Note that this cannot grow the Pickle's capacity and
+  // it is an error to Allocate() more bytes in total than have been
+  // pre-allocated using ReserveCapacity() or ReserveUninitializedCapacity().
+  //
+  // This guarantees that the returned data is aligned on an 8-byte boundary.
+  void* Allocate(size_t num_bytes) override;
+
+  scoped_ptr<Storage> storage_;
+
+  DISALLOW_COPY_AND_ASSIGN(PickleBuffer);
+};
+
+}  // namespace internal
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_PICKLE_BUFFER_H_