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. SyncSocket(Handle handle)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. handle()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); ~CancelableSyncSocket()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_ 142