Add non-blocking peek for the syncsocket...

base/sync_socket.h

 // Copyright (c) 2009 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 BASE_SYNC_SOCKET_H_
 #define BASE_SYNC_SOCKET_H_
 
 // A socket abstraction used for sending and receiving plain
 // data.  Because they are blocking, they can be used to perform
 // rudimentary cross-process synchronization with low latency.
@@ skipping 33 matching lines @@
   // length is the length of the data to send (must be non-zero).
   // Returns the number of bytes sent, or 0 upon failure.
   size_t Send(const void* buffer, size_t length);
 
   // Receives a message from an SyncSocket.
   // buffer is a pointer to the buffer to receive data.
   // length is the number of bytes of data to receive (must be non-zero).
   // Returns the number of bytes received, or 0 upon failure.
   size_t Receive(void* buffer, size_t length);
 
+  // Returns the number of bytes available. If non-zero, Receive() will not
+  // not block when called. NOTE: Some implementations cannot reliably
+  // determine the number of bytes available so avoid using the returned
+  // size as a promise and simply test against zero.
+  size_t Peek();
+
   // Extracts the contained handle.  Used for transferring between
   // processes.
   Handle handle() const { return handle_; }
 
  private:
   Handle handle_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncSocket);
 };
 
 }  // namespace base
 
 #endif  // BASE_SYNC_SOCKET_H_