base/sync_socket.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_SYNC_SOCKET_H_
   6 #define BASE_SYNC_SOCKET_H_
   7 #pragma once
   8
   9 // A socket abstraction used for sending and receiving plain
  10 // data.  Because they are blocking, they can be used to perform
  11 // rudimentary cross-process synchronization with low latency.
  12
  13 #include "base/basictypes.h"
  14 #if defined(OS_WIN)
  15 #include <windows.h>
  16 #endif
  17 #include <sys/types.h>
  18
  19 #include "base/base_export.h"
  20 #include "base/compiler_specific.h"
  21 #include "base/synchronization/waitable_event.h"
  22
  23 namespace base {
  24
  25 class BASE_EXPORT SyncSocket {
  26  public:
  27 #if defined(OS_WIN)
  28   typedef HANDLE Handle;
  29 #else
  30   typedef int Handle;
  31 #endif
  32   static const Handle kInvalidHandle;
  33
  34   SyncSocket();
  35
  36   // Creates a SyncSocket from a Handle.  Used in transport.
  37   explicit SyncSocket(Handle handle) : handle_(handle)  {}
  38   virtual ~SyncSocket();
  39
  40   // Initializes and connects a pair of sockets.
  41   // |socket_a| and |socket_b| must not hold a valid handle.  Upon successful
  42   // return, the sockets will both be valid and connected.
  43   static bool CreatePair(SyncSocket* socket_a, SyncSocket* socket_b);
  44
  45   // Closes the SyncSocket.  Returns true on success, false on failure.
  46   virtual bool Close();
  47
  48   // Sends the message to the remote peer of the SyncSocket.
  49   // Note it is not safe to send messages from the same socket handle by
  50   // multiple threads simultaneously.
  51   // buffer is a pointer to the data to send.
  52   // length is the length of the data to send (must be non-zero).
  53   // Returns the number of bytes sent, or 0 upon failure.
  54   virtual size_t Send(const void* buffer, size_t length);
  55
  56   // Receives a message from an SyncSocket.
  57   // buffer is a pointer to the buffer to receive data.
  58   // length is the number of bytes of data to receive (must be non-zero).
  59   // Returns the number of bytes received, or 0 upon failure.
  60   virtual size_t Receive(void* buffer, size_t length);
  61
  62   // Returns the number of bytes available. If non-zero, Receive() will not
  63   // not block when called. NOTE: Some implementations cannot reliably
  64   // determine the number of bytes available so avoid using the returned
  65   // size as a promise and simply test against zero.
  66   size_t Peek();
  67
  68   // Extracts the contained handle.  Used for transferring between
  69   // processes.
  70   Handle handle() const { return handle_; }
  71
  72  protected:
  73   Handle handle_;
  74
  75  private:
  76   DISALLOW_COPY_AND_ASSIGN(SyncSocket);
  77 };
  78
  79 // Derives from SyncSocket and adds support for shutting down the socket from
  80 // another thread while a blocking Receive or Send is being done from the thread
  81 // that owns the socket.
  82 class BASE_EXPORT CancelableSyncSocket : public SyncSocket {
  83  public:
  84   CancelableSyncSocket();
  85   explicit CancelableSyncSocket(Handle handle);
  86   virtual ~CancelableSyncSocket() {}
  87
  88   // Initializes a pair of cancelable sockets.  See documentation for
  89   // SyncSocket::CreatePair for more details.
  90   static bool CreatePair(CancelableSyncSocket* socket_a,
  91                          CancelableSyncSocket* socket_b);
  92
  93   // A way to shut down a socket even if another thread is currently performing
  94   // a blocking Receive or Send.
  95   bool Shutdown();
  96
  97 #if defined(OS_WIN)
  98   // Since the Linux and Mac implementations actually use a socket, shutting
  99   // them down from another thread is pretty simple - we can just call
 100   // shutdown().  However, the Windows implementation relies on named pipes
 101   // and there isn't a way to cancel a blocking synchronous Read that is
 102   // supported on <Vista. So, for Windows only, we override these
 103   // SyncSocket methods in order to support shutting down the 'socket'.
 104   virtual bool Close() OVERRIDE;
 105   virtual size_t Send(const void* buffer, size_t length) OVERRIDE;
 106   virtual size_t Receive(void* buffer, size_t length) OVERRIDE;
 107 #endif
 108
 109  private:
 110 #if defined(OS_WIN)
 111   WaitableEvent shutdown_event_;
 112   WaitableEvent file_operation_;
 113 #endif
 114   DISALLOW_COPY_AND_ASSIGN(CancelableSyncSocket);
 115 };
 116
 117 }  // namespace base
 118
 119 #endif  // BASE_SYNC_SOCKET_H_