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 #include "base/time/time.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   // Same as Receive() but only blocks for data until |timeout| has elapsed or
  63   // |buffer| |length| is exhausted.  Currently only timeouts less than one
  64   // second are allowed.  Return the amount of data read.
  65   virtual size_t ReceiveWithTimeout(void* buffer,
  66                                     size_t length,
  67                                     TimeDelta timeout);
  68
  69   // Returns the number of bytes available. If non-zero, Receive() will not
  70   // not block when called. NOTE: Some implementations cannot reliably
  71   // determine the number of bytes available so avoid using the returned
  72   // size as a promise and simply test against zero.
  73   size_t Peek();
  74
  75   // Extracts the contained handle.  Used for transferring between
  76   // processes.
  77   Handle handle() const { return handle_; }
  78
  79  protected:
  80   Handle handle_;
  81
  82  private:
  83   DISALLOW_COPY_AND_ASSIGN(SyncSocket);
  84 };
  85
  86 // Derives from SyncSocket and adds support for shutting down the socket from
  87 // another thread while a blocking Receive or Send is being done from the
  88 // thread that owns the socket.
  89 class BASE_EXPORT CancelableSyncSocket : public SyncSocket {
  90  public:
  91   CancelableSyncSocket();
  92   explicit CancelableSyncSocket(Handle handle);
  93   virtual ~CancelableSyncSocket() {}
  94
  95   // Initializes a pair of cancelable sockets.  See documentation for
  96   // SyncSocket::CreatePair for more details.
  97   static bool CreatePair(CancelableSyncSocket* socket_a,
  98                          CancelableSyncSocket* socket_b);
  99
 100   // A way to shut down a socket even if another thread is currently performing
 101   // a blocking Receive or Send.
 102   bool Shutdown();
 103
 104 #if defined(OS_WIN)
 105   // Since the Linux and Mac implementations actually use a socket, shutting
 106   // them down from another thread is pretty simple - we can just call
 107   // shutdown().  However, the Windows implementation relies on named pipes
 108   // and there isn't a way to cancel a blocking synchronous Read that is
 109   // supported on <Vista. So, for Windows only, we override these
 110   // SyncSocket methods in order to support shutting down the 'socket'.
 111   virtual bool Close() OVERRIDE;
 112   virtual size_t Receive(void* buffer, size_t length) OVERRIDE;
 113   virtual size_t ReceiveWithTimeout(void* buffer,
 114                                     size_t length,
 115                                     TimeDelta timeout) OVERRIDE;
 116 #endif
 117
 118   // Send() is overridden to catch cases where the remote end is not responding
 119   // and we fill the local socket buffer. When the buffer is full, this
 120   // implementation of Send() will not block indefinitely as
 121   // SyncSocket::Send will, but instead return 0, as no bytes could be sent.
 122   // Note that the socket will not be closed in this case.
 123   virtual size_t Send(const void* buffer, size_t length) OVERRIDE;
 124
 125  private:
 126 #if defined(OS_WIN)
 127   WaitableEvent shutdown_event_;
 128   WaitableEvent file_operation_;
 129 #endif
 130   DISALLOW_COPY_AND_ASSIGN(CancelableSyncSocket);
 131 };
 132
 133 #if defined(OS_WIN) && !defined(COMPONENT_BUILD)
 134 // TODO(cpu): remove this once chrome is split in two dlls.
 135 __declspec(selectany)
 136     const SyncSocket::Handle SyncSocket::kInvalidHandle = INVALID_HANDLE_VALUE;
 137 #endif
 138
 139 }  // namespace base
 140
 141 #endif  // BASE_SYNC_SOCKET_H_