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
   8 // A socket abstraction used for sending and receiving plain
   9 // data.  Because the receiving is blocking, they can be used to perform
  10 // rudimentary cross-process synchronization with low latency.
  11
  12 #include "base/basictypes.h"
  13 #if defined(OS_WIN)
  14 #include <windows.h>
  15 #endif
  16 #include <sys/types.h>
  17
  18 #include "base/base_export.h"
  19 #include "base/compiler_specific.h"
  20 #include "base/synchronization/waitable_event.h"
  21
  22 namespace base {
  23
  24 class BASE_EXPORT SyncSocket {
  25  public:
  26 #if defined(OS_WIN)
  27   typedef HANDLE Handle;
  28 #else
  29   typedef int Handle;
  30 #endif
  31   static const Handle kInvalidHandle;
  32
  33   SyncSocket();
  34
  35   // Creates a SyncSocket from a Handle.  Used in transport.
  36   explicit SyncSocket(Handle handle) : handle_(handle)  {}
  37   virtual ~SyncSocket();
  38
  39   // Initializes and connects a pair of sockets.
  40   // |socket_a| and |socket_b| must not hold a valid handle.  Upon successful
  41   // return, the sockets will both be valid and connected.
  42   static bool CreatePair(SyncSocket* socket_a, SyncSocket* socket_b);
  43
  44   // Closes the SyncSocket.  Returns true on success, false on failure.
  45   virtual bool Close();
  46
  47   // Sends the message to the remote peer of the SyncSocket.
  48   // Note it is not safe to send messages from the same socket handle by
  49   // multiple threads simultaneously.
  50   // buffer is a pointer to the data to send.
  51   // length is the length of the data to send (must be non-zero).
  52   // Returns the number of bytes sent, or 0 upon failure.
  53   virtual size_t Send(const void* buffer, size_t length);
  54
  55   // Receives a message from an SyncSocket.
  56   // buffer is a pointer to the buffer to receive data.
  57   // length is the number of bytes of data to receive (must be non-zero).
  58   // Returns the number of bytes received, or 0 upon failure.
  59   virtual size_t Receive(void* buffer, size_t length);
  60
  61   // Returns the number of bytes available. If non-zero, Receive() will not
  62   // not block when called. NOTE: Some implementations cannot reliably
  63   // determine the number of bytes available so avoid using the returned
  64   // size as a promise and simply test against zero.
  65   size_t Peek();
  66
  67   // Extracts the contained handle.  Used for transferring between
  68   // processes.
  69   Handle handle() const { return handle_; }
  70
  71  protected:
  72   Handle handle_;
  73
  74  private:
  75   DISALLOW_COPY_AND_ASSIGN(SyncSocket);
  76 };
  77
  78 // Derives from SyncSocket and adds support for shutting down the socket from
  79 // another thread while a blocking Receive or Send is being done from the
  80 // thread that owns the socket.
  81 class BASE_EXPORT CancelableSyncSocket : public SyncSocket {
  82  public:
  83   CancelableSyncSocket();
  84   explicit CancelableSyncSocket(Handle handle);
  85   virtual ~CancelableSyncSocket() {}
  86
  87   // Initializes a pair of cancelable sockets.  See documentation for
  88   // SyncSocket::CreatePair for more details.
  89   static bool CreatePair(CancelableSyncSocket* socket_a,
  90                          CancelableSyncSocket* socket_b);
  91
  92   // A way to shut down a socket even if another thread is currently performing
  93   // a blocking Receive or Send.
  94   bool Shutdown();
  95
  96 #if defined(OS_WIN)
  97   // Since the Linux and Mac implementations actually use a socket, shutting
  98   // them down from another thread is pretty simple - we can just call
  99   // shutdown().  However, the Windows implementation relies on named pipes
 100   // and there isn't a way to cancel a blocking synchronous Read that is
 101   // supported on <Vista. So, for Windows only, we override these
 102   // SyncSocket methods in order to support shutting down the 'socket'.
 103   virtual bool Close() OVERRIDE;
 104   virtual size_t Receive(void* buffer, size_t length) OVERRIDE;
 105 #endif
 106
 107   // Send() is overridden to catch cases where the remote end is not responding
 108   // and we fill the local socket buffer. When the buffer is full, this
 109   // implementation of Send() will not block indefinitely as
 110   // SyncSocket::Send will, but instead return 0, as no bytes could be sent.
 111   // Note that the socket will not be closed in this case.
 112   virtual size_t Send(const void* buffer, size_t length) OVERRIDE;
 113
 114  private:
 115 #if defined(OS_WIN)
 116   WaitableEvent shutdown_event_;
 117   WaitableEvent file_operation_;
 118 #endif
 119   DISALLOW_COPY_AND_ASSIGN(CancelableSyncSocket);
 120 };
 121
 122 }  // namespace base
 123
 124 #endif  // BASE_SYNC_SOCKET_H_