Add support to be able to asynchronously read from a CancelableSyncSocket

media/audio/async_socket_io_handler_win.cc

+// Copyright (c) 2012 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 "media/audio/async_socket_io_handler.h"
+
+namespace media {
+
+AsyncSocketIoHandler::AsyncSocketIoHandler()
+    : socket_(base::SyncSocket::kInvalidHandle),
+      context_(NULL) {}
+
+AsyncSocketIoHandler::~AsyncSocketIoHandler() {
+  // We need to be deleted on the correct thread to avoid racing with the
+  // message loop thread.
+  DCHECK(CalledOnValidThread());
+
+  if (context_) {
+    if (!read_complete_.is_null()) {
+      // Make the context be deleted by the message pump when done.
+      context_->handler = NULL;
+    } else {
+      delete context_;
+    }
+  }
+}
+
+// Implementation of IOHandler on Windows.
+void AsyncSocketIoHandler::OnIOCompleted(MessageLoopForIO::IOContext* context,
+                                         DWORD bytes_transfered,
+                                         DWORD error) {
+  DCHECK(CalledOnValidThread());
+  DCHECK_EQ(context_, context);
+  if (!read_complete_.is_null()) {
+    read_complete_.Run(error == ERROR_SUCCESS ? bytes_transfered : 0);
+    read_complete_.Reset();
+  }
+}
+
+bool AsyncSocketIoHandler::Read(char* buffer, int buffer_len,
+                                const ReadCompleteCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  DCHECK(read_complete_.is_null());
+  DCHECK_NE(socket_, base::SyncSocket::kInvalidHandle);
+
+  read_complete_ = callback;
+
+  DWORD bytes_read = 0;
+  BOOL ok = ::ReadFile(socket_, buffer, buffer_len, &bytes_read,
+                       &context_->overlapped);
+  // The completion port will be signaled regardless of completing the read
+  // straight away or asynchronously (ERROR_IO_PENDING). OnIOCompleted() will
+  // be called regardless and we don't need to explicitly run the callback
+  // in the case where ok is FALSE and GLE==ERROR_IO_PENDING.
+  return ok || GetLastError() == ERROR_IO_PENDING;
+}
+
+bool AsyncSocketIoHandler::Initialize(base::SyncSocket::Handle socket) {
+  DCHECK(!context_);
+  DCHECK_EQ(socket_, base::SyncSocket::kInvalidHandle);
+
+  DetachFromThread();
+
+  socket_ = socket;
+  MessageLoopForIO::current()->RegisterIOHandler(socket, this);
+
+  context_ = new MessageLoopForIO::IOContext();
+  context_->handler = this;
+  memset(&context_->overlapped, 0, sizeof(context_->overlapped));
+
+  return true;
+}
+
+}  // namespace media.