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

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

Index: mojo/public/cpp/bindings/lib/message.cc
diff --git a/mojo/public/cpp/bindings/lib/message.cc b/mojo/public/cpp/bindings/lib/message.cc
index 6b563e779aca7d196284726c0a899fe03ce2cdde..ba7f21b8395d17bbb5fc2043a2206d79be9855d5 100644
--- a/mojo/public/cpp/bindings/lib/message.cc
+++ b/mojo/public/cpp/bindings/lib/message.cc
@@ -17,36 +17,31 @@ Message::Message() {
 }
 
 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();
@@ -54,13 +49,10 @@ void Message::MoveTo(Message* destination) {
 }
 
 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())
@@ -85,15 +77,16 @@ MojoResult ReadAndDispatchMessage(MessagePipeHandle handle,
 
   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)