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 #if defined(OS_WIN) && !defined(COMPONENT_BUILD) 123 // TODO(cpu): remove this once chrome is split in two dlls. 124 __declspec(selectany) 125 const SyncSocket::Handle SyncSocket::kInvalidHandle = INVALID_HANDLE_VALUE; 126 #endif 127 128 } // namespace base 129 130 #endif // BASE_SYNC_SOCKET_H_ 131