Mojo: Use new message APIs to reduce copying

mojo/public/cpp/bindings/message.h

 // Copyright 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 MOJO_PUBLIC_CPP_BINDINGS_MESSAGE_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_MESSAGE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <limits>
 #include <memory>
 #include <vector>
 
 #include "base/logging.h"
+#include "mojo/public/cpp/bindings/lib/message_buffer.h"
 #include "mojo/public/cpp/bindings/lib/message_internal.h"
-#include "mojo/public/cpp/bindings/lib/pickle_buffer.h"
+#include "mojo/public/cpp/system/message.h"
 
 namespace mojo {
 
 // Message is a holder for the data and handles to be sent over a MessagePipe.
 // Message owns its data and handles, but a consumer of Message is free to
 // mutate the data and handles. The message's data is comprised of a header
 // followed by payload.
 class Message {
  public:
   Message();
   ~Message();
 
+  // Initializes a Message with enough space for |capacity| bytes.
   void Initialize(size_t capacity, bool zero_initialized);
 
+  // Initializes a Message from an existing Mojo MessageHandle.
+  void InitializeFromMojoMessage(ScopedMessageHandle message,
+                                 uint32_t num_bytes,
+                                 std::vector<Handle>* handles);
+
   // Transfers data and handles to |destination|.
   void MoveTo(Message* destination);
 
-  uint32_t data_num_bytes() const {
-    DCHECK(buffer_->data_num_bytes() <= std::numeric_limits<uint32_t>::max());
-    return static_cast<uint32_t>(buffer_->data_num_bytes());
-  }
+  uint32_t data_num_bytes() const { return buffer_->data_num_bytes(); }
 
   // Access the raw bytes of the message.
   const uint8_t* data() const {
     return static_cast<const uint8_t*>(buffer_->data());
   }
 
   uint8_t* mutable_data() { return static_cast<uint8_t*>(buffer_->data()); }
 
   // Access the header.
   const internal::MessageHeader* header() const {
@@ skipping 34 matching lines @@
     return static_cast<uint32_t>(num_bytes);
   }
 
   // Access the handles.
   const std::vector<Handle>* handles() const { return &handles_; }
   std::vector<Handle>* mutable_handles() { return &handles_; }
 
   // Access the underlying Buffer interface.
   internal::Buffer* buffer() { return buffer_.get(); }
 
+  // Takes a scoped MessageHandle which may be passed to |WriteMessageNew()| for
+  // transmission. Note that this invalidates this Message object, taking
+  // ownership of its internal storage and any attached handles.
+  ScopedMessageHandle TakeMojoMessage();
+
  private:
   void CloseHandles();
 
-  std::unique_ptr<internal::PickleBuffer> buffer_;
+  std::unique_ptr<internal::MessageBuffer> buffer_;
   std::vector<Handle> handles_;
 
   DISALLOW_COPY_AND_ASSIGN(Message);
 };
 
 class MessageReceiver {
  public:
   virtual ~MessageReceiver() {}
 
   // The receiver may mutate the given message.  Returns true if the message
@@ skipping 66 matching lines @@
 // the caller should wait on the handle to become readable. Returns
 // MOJO_RESULT_OK if the message was read successfully and should be
 // dispatched, otherwise returns an error code if something went wrong.
 //
 // NOTE: The message hasn't been validated and may be malformed!
 MojoResult ReadMessage(MessagePipeHandle handle, Message* message);
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_MESSAGE_H_