Add support to be able to asynchronously read from a CancelableSyncSocket

media/audio/async_socket_io_handler.h

+// 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.
+
+#ifndef MEDIA_AUDIO_ASYNC_SOCKET_IO_HANDLER_H_
+#define MEDIA_AUDIO_ASYNC_SOCKET_IO_HANDLER_H_
+
+#include "base/message_loop.h"
+#include "base/sync_socket.h"
+#include "base/threading/non_thread_safe.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+// The message loop callback interface is different based on platforms.
+#if defined(OS_WIN)
+typedef MessageLoopForIO::IOHandler MessageLoopIOHandler;
+#elif defined(OS_POSIX)
+typedef MessageLoopForIO::Watcher MessageLoopIOHandler;
+#endif
+
+// Extends the CancelableSyncSocket class to allow reading from a socket
+// asynchronously on a TYPE_IO message loop thread.  This makes it easy to share
+// a thread that uses a message loop (e.g. for IPC and other things) and not
+// require a separate thread to read from the socket.
+//
+// Example usage (also see the unit tests):
+//
+// class SocketReader {
+//  public:
+//   SocketReader(base::CancelableSyncSocket* socket)
+//       : socket_(socket), buffer_() {
+//     io_handler.Initialize(socket_->handle());
+//   }
+//
+//   void AsyncRead() {
+//     CHECK(io_handler.Read(&buffer_[0], sizeof(buffer_),
+//                           base::Bind(&SocketReader::OnDataAvailable,
+//                                      base::Unretained(this)));
+//   }
+//
+//  private:
+//   void OnDataAvailable(int bytes_read) {
+//     ProcessData(&buffer_[0], bytes_read);
+//   }
+//
+//   media::AsyncSocketIoHandler io_handler;
+//   base::CancelableSyncSocket* socket_;
+//   char buffer_[kBufferSize];
+// };
+//
+class MEDIA_EXPORT AsyncSocketIoHandler
+    : public base::NonThreadSafe,
+      public MessageLoopIOHandler {
+ public:
+  AsyncSocketIoHandler();
+  virtual ~AsyncSocketIoHandler();
+
+  // Initializes the AsyncSocketIoHandler by hooking it up to the current
+  // thread's message loop (must be TYPE_IO), to do async reads from the socket
+  // on the current thread.
+  bool Initialize(base::SyncSocket::Handle socket);
+
+  // Type definition for the callback. The parameter tells how many
+  // bytes were read and is 0 if an error occurred.
+  typedef base::Callback<void(int)> ReadCompleteCallback;
+
+  // Attempts to read from the socket.  The return value will be |false|
+  // if an error occurred and |true| if data was read or a pending read
+  // was issued.  Regardless of async or sync operation, the callback will
+  // be called when data is available.
+  bool Read(char* buffer, int buffer_len,
+            const ReadCompleteCallback& callback);
+
+ private:
+#if defined(OS_WIN)
+  // Implementation of IOHandler on Windows.
+  virtual void OnIOCompleted(MessageLoopForIO::IOContext* context,
+                             DWORD bytes_transfered,
+                             DWORD error) OVERRIDE;
+#elif defined(OS_POSIX)
+  // Implementation of MessageLoopForIO::Watcher.
+  virtual void OnFileCanWriteWithoutBlocking(int socket) OVERRIDE {}
+  virtual void OnFileCanReadWithoutBlocking(int socket) OVERRIDE;
+
+  void EnsureWatchingSocket();
+#endif
+
+  base::SyncSocket::Handle socket_;
+#if defined(OS_WIN)
+  MessageLoopForIO::IOContext* context_;
+#elif defined(OS_POSIX)
+  MessageLoopForIO::FileDescriptorWatcher socket_watcher_;
+  // |pending_buffer_| and |pending_buffer_len_| are valid only between
+  // Read() and OnFileCanReadWithoutBlocking().
+  char* pending_buffer_;
+  int pending_buffer_len_;
+  // |true| iff the message loop is watching the socket for IO events.
+  bool is_watching_;
+#endif
+  ReadCompleteCallback read_complete_;
+
+  DISALLOW_COPY_AND_ASSIGN(AsyncSocketIoHandler);
+};
+
+}  // namespace media.
+
+#endif  // MEDIA_AUDIO_ASYNC_SOCKET_IO_HANDLER_H_