Mojo: WebSocket interface now reuses the DataPipe for subsequent sends or

mojo/services/public/cpp/network/web_socket_write_queue.cc

+// 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.
+
+#include "mojo/services/public/cpp/network/web_socket_write_queue.h"
+
+#include "base/bind.h"
+
+namespace mojo {
+
+struct WebSocketWriteQueue::Operation {
+  uint32_t num_bytes_;
+  base::Callback<void(const char*)> callback_;
+
+  const char* data_;
+  // Only initialized if the initial Write fails. This saves a copy in
+  // the common case.
+  std::vector<char> data_copy_;
+};
+
+WebSocketWriteQueue::WebSocketWriteQueue(DataPipeProducerHandle handle)
+    : handle_(handle), is_waiting_(false) {
+}
+
+WebSocketWriteQueue::~WebSocketWriteQueue() {
+}
+
+void WebSocketWriteQueue::Write(const char* data,
+                                uint32_t num_bytes,
+                                base::Callback<void(const char*)> callback) {
+  Operation* op = new Operation;
+  op->num_bytes_ = num_bytes;
+  op->callback_ = callback;
+  op->data_ = data;
+  queue_.push_back(op);
+
+  MojoResult result = MOJO_RESULT_SHOULD_WAIT;
+  if (!is_waiting_)
+    result = TryToWrite();
+
+  // If we have to wait, make a local copy of the data so we know it will
+  // live until we need it.
+  if (result == MOJO_RESULT_SHOULD_WAIT) {
+    op->data_copy_.resize(num_bytes);
+    memcpy(&op->data_copy_[0], data, num_bytes);
+    op->data_ = &op->data_copy_[0];
+  }
+}
+
+MojoResult WebSocketWriteQueue::TryToWrite() {
+  Operation* op = queue_[0];
+  uint32_t bytes_written = op->num_bytes_;
+  MojoResult result = WriteDataRaw(
+      handle_, op->data_, &bytes_written, MOJO_WRITE_DATA_FLAG_ALL_OR_NONE);
+  if (result == MOJO_RESULT_SHOULD_WAIT) {
+    Wait();
+    return result;
+  }
+
+  // Ensure |op| is deleted, whether or not |this| goes away.
+  scoped_ptr<Operation> op_deleter(op);
+  queue_.weak_erase(queue_.begin());
+  if (result != MOJO_RESULT_OK)
+    return result;
+
+  op->callback_.Run(op->data_);  // may delete |this|
+  return result;
+}
+
+void WebSocketWriteQueue::Wait() {
+  is_waiting_ = true;
+  handle_watcher_.Start(handle_,
+                        MOJO_HANDLE_SIGNAL_WRITABLE,
+                        MOJO_DEADLINE_INDEFINITE,
+                        base::Bind(&WebSocketWriteQueue::OnHandleReady,
+                                   base::Unretained(this)));
+}
+
+void WebSocketWriteQueue::OnHandleReady(MojoResult result) {
+  is_waiting_ = false;
+  TryToWrite();
+}
+
+}  // namespace mojo