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

mojo/public/cpp/bindings/lib/message.cc

 // Copyright 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.
 
 #include "mojo/public/cpp/bindings/message.h"
 
 #include <stdlib.h>
 
 #include <algorithm>
 
 #include "mojo/public/cpp/environment/logging.h"
 
 namespace mojo {
 
 Message::Message() {
   Initialize();
 }
 
 Message::~Message() {
-  FreeDataAndCloseHandles();
+  CloseHandles();
 }
 
 void Message::Reset() {
-  FreeDataAndCloseHandles();
+  CloseHandles();
 
   handles_.clear();
   Initialize();
 }
 
 void Message::AllocData(uint32_t num_bytes) {
-  MOJO_DCHECK(!data_);
-  data_num_bytes_ = num_bytes;
-  data_ = static_cast<internal::MessageData*>(calloc(num_bytes, 1));
+  buffer_->AllocData(num_bytes);
 }
 
 void Message::AllocUninitializedData(uint32_t num_bytes) {
-  MOJO_DCHECK(!data_);
-  data_num_bytes_ = num_bytes;
-  data_ = static_cast<internal::MessageData*>(malloc(num_bytes));
+  buffer_->AllocUninitializedData(num_bytes);
 }
 
 void Message::MoveTo(Message* destination) {
   MOJO_DCHECK(this != destination);
 

[yzshen1, 2015/12/15 19:07:02]

Please consider removing line 41 and 47-48, and replacing them with a  Reset()
call at the end.

-  destination->FreeDataAndCloseHandles();
+  destination->CloseHandles();
 
   // No copy needed.
-  destination->data_num_bytes_ = data_num_bytes_;
-  destination->data_ = data_;
+  std::swap(destination->buffer_, buffer_);
   std::swap(destination->handles_, handles_);
 
   handles_.clear();
   Initialize();
 }
 
 void Message::Initialize() {
-  data_num_bytes_ = 0;
-  data_ = nullptr;
+  buffer_.reset(new internal::PickleBuffer);
 }
 
-void Message::FreeDataAndCloseHandles() {
-  free(data_);
-
+void Message::CloseHandles() {
   for (std::vector<Handle>::iterator it = handles_.begin();
        it != handles_.end(); ++it) {
     if (it->is_valid())
       CloseRaw(*it);
   }
 }
 
 MojoResult ReadAndDispatchMessage(MessagePipeHandle handle,
                                   MessageReceiver* receiver,
                                   bool* receiver_result) {
   MojoResult rv;
 
   uint32_t num_bytes = 0, num_handles = 0;
   rv = ReadMessageRaw(handle,
                       nullptr,
                       &num_bytes,
                       nullptr,
                       &num_handles,
                       MOJO_READ_MESSAGE_FLAG_NONE);
   if (rv != MOJO_RESULT_RESOURCE_EXHAUSTED)
     return rv;
 
   Message message;
   message.AllocUninitializedData(num_bytes);
+  void* mutable_data = message.buffer()->Allocate(num_bytes);

[yzshen1, 2015/12/15 19:07:02]

It seems fairly confusing to require two allocate in a row. Without looking at
the code carefully, now I don't know whether I can access Message::data() before
doing message.buffer()->Allocate(), for example.

   message.mutable_handles()->resize(num_handles);
 
   rv = ReadMessageRaw(
       handle,
-      message.mutable_data(),
+      mutable_data,
       &num_bytes,
       message.mutable_handles()->empty()
           ? nullptr
-          : reinterpret_cast<MojoHandle*>(&message.mutable_handles()->front()),
+          : reinterpret_cast<MojoHandle*>(message.mutable_handles()->data()),
       &num_handles,
       MOJO_READ_MESSAGE_FLAG_NONE);
   if (receiver && rv == MOJO_RESULT_OK)
     *receiver_result = receiver->Accept(&message);
 
   return rv;
 }
 
 }  // namespace mojo