[GCM] Add RMQ storage and MCS message passing support

google_apis/gcm/base/mcs_message.h

Index: google_apis/gcm/base/mcs_message.h
diff --git a/google_apis/gcm/base/mcs_message.h b/google_apis/gcm/base/mcs_message.h
new file mode 100644
index 0000000000000000000000000000000000000000..241c75d131140154f0087916f5383adc6e31ce91
--- /dev/null
+++ b/google_apis/gcm/base/mcs_message.h
@@ -0,0 +1,85 @@
+// Copyright (c) 2013 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 GOOGLE_APIS_GCM_BASE_MCS_MESSAGE_H_
+#define GOOGLE_APIS_GCM_BASE_MCS_MESSAGE_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "google_apis/gcm/base/gcm_export.h"
+
+namespace google {
+namespace protobuf {
+class MessageLite;
+}  // namespace protobuf
+}  // namespace google
+
+namespace gcm {
+
+// A wrapper for MCS protobuffers that encapsulates their tag, size and data
+// in an immutable and thread-safe format. If a mutable version is desired,
+// CloneProtobuf() should use used to create a new copy of the protobuf.
+//
+// Note: default copy and assign welcome.
+class GCM_EXPORT MCSMessage {
+ public:
+  // Creates an invalid MCSMessage.
+  MCSMessage();
+  // Infers tag from |message|.
+  explicit MCSMessage(const google::protobuf::MessageLite& protobuf);
+  // |tag| must match |protobuf|'s message type.
+  MCSMessage(uint8 tag, const google::protobuf::MessageLite& protobuf);
+  // |tag| must match |protobuf|'s message type. Takes ownership of |protobuf|.
+  MCSMessage(uint8 tag,
+             scoped_ptr<const google::protobuf::MessageLite> protobuf);
+  ~MCSMessage();
+
+  // Returns whether this message is valid or not (whether a protobuf was
+  // provided at construction time or not).
+  bool IsValid() const;
+
+  // Getters for serialization.
+  uint8 tag() const { return tag_; }
+  int size() const {return size_; }
+  std::string SerializeAsString() const;
+
+  // Getter for accessing immutable probotuf fields.
+  const google::protobuf::MessageLite& GetProtobuf() const;
+
+  // Getter for creating a mutated version of the protobuf.
+  scoped_ptr<google::protobuf::MessageLite> CloneProtobuf() const;
+
+ private:
+  class Core : public base::RefCountedThreadSafe<MCSMessage::Core> {
+   public:
+    Core();
+    Core(uint8 tag, const google::protobuf::MessageLite& protobuf);
+    Core(uint8 tag, scoped_ptr<const google::protobuf::MessageLite> protobuf);
+
+    const google::protobuf::MessageLite& Get() const;
+
+   private:
+    friend class base::RefCountedThreadSafe<MCSMessage::Core>;
+    ~Core();
+
+    // The immutable protobuf.
+    scoped_ptr<const google::protobuf::MessageLite> protobuf_;
+
+    DISALLOW_COPY_AND_ASSIGN(Core);
+  };
+
+  // These are cached separately to avoid having to recompute them.
+  const uint8 tag_;
+  const int size_;
+
+  // The refcounted core, containing the protobuf memory.
+  scoped_refptr<const Core> core_;
+};
+
+}  // namespace gcm
+
+#endif  // GOOGLE_APIS_GCM_BASE_MCS_MESSAGE_H_