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/process/process_handle.h" 21 #include "base/synchronization/waitable_event.h" 22 #include "base/time/time.h" 23 24 #if defined(OS_POSIX) 25 #include "base/file_descriptor_posix.h" 26 #endif 27 28 namespace base { 29 30 class BASE_EXPORT SyncSocket { 31 public: 32 #if defined(OS_WIN) 33 typedef HANDLE Handle; 34 typedef Handle TransitDescriptor; 35 #else 36 typedef int Handle; 37 typedef FileDescriptor TransitDescriptor; 38 #endif 39 static const Handle kInvalidHandle; 40 41 SyncSocket(); 42 43 // Creates a SyncSocket from a Handle. Used in transport. 44 explicit SyncSocket(Handle handle) : handle_(handle) {} 45 virtual ~SyncSocket(); 46 47 // Initializes and connects a pair of sockets. 48 // |socket_a| and |socket_b| must not hold a valid handle. Upon successful 49 // return, the sockets will both be valid and connected. 50 static bool CreatePair(SyncSocket* socket_a, SyncSocket* socket_b); 51 52 // Returns |Handle| wrapped in a |TransitDescriptor|. 53 static Handle UnwrapHandle(const TransitDescriptor& descriptor); 54 55 // Prepares a |TransitDescriptor| which wraps |Handle| used for transit. 56 // This is used to prepare the underlying shared resource before passing back 57 // the handle to be used by the peer process. 58 bool PrepareTransitDescriptor(ProcessHandle peer_process_handle, 59 TransitDescriptor* descriptor); 60 61 // Closes the SyncSocket. Returns true on success, false on failure. 62 virtual bool Close(); 63 64 // Sends the message to the remote peer of the SyncSocket. 65 // Note it is not safe to send messages from the same socket handle by 66 // multiple threads simultaneously. 67 // buffer is a pointer to the data to send. 68 // length is the length of the data to send (must be non-zero). 69 // Returns the number of bytes sent, or 0 upon failure. 70 virtual size_t Send(const void* buffer, size_t length); 71 72 // Receives a message from an SyncSocket. 73 // buffer is a pointer to the buffer to receive data. 74 // length is the number of bytes of data to receive (must be non-zero). 75 // Returns the number of bytes received, or 0 upon failure. 76 virtual size_t Receive(void* buffer, size_t length); 77 78 // Same as Receive() but only blocks for data until |timeout| has elapsed or 79 // |buffer| |length| is exhausted. Currently only timeouts less than one 80 // second are allowed. Return the amount of data read. 81 virtual size_t ReceiveWithTimeout(void* buffer, 82 size_t length, 83 TimeDelta timeout); 84 85 // Returns the number of bytes available. If non-zero, Receive() will not 86 // not block when called. NOTE: Some implementations cannot reliably 87 // determine the number of bytes available so avoid using the returned 88 // size as a promise and simply test against zero. 89 size_t Peek(); 90 91 // Extracts the contained handle. Used for transferring between 92 // processes. 93 Handle handle() const { return handle_; } 94 95 protected: 96 Handle handle_; 97 98 private: 99 DISALLOW_COPY_AND_ASSIGN(SyncSocket); 100 }; 101 102 // Derives from SyncSocket and adds support for shutting down the socket from 103 // another thread while a blocking Receive or Send is being done from the 104 // thread that owns the socket. 105 class BASE_EXPORT CancelableSyncSocket : public SyncSocket { 106 public: 107 CancelableSyncSocket(); 108 explicit CancelableSyncSocket(Handle handle); 109 virtual ~CancelableSyncSocket() {} 110 111 // Initializes a pair of cancelable sockets. See documentation for 112 // SyncSocket::CreatePair for more details. 113 static bool CreatePair(CancelableSyncSocket* socket_a, 114 CancelableSyncSocket* socket_b); 115 116 // A way to shut down a socket even if another thread is currently performing 117 // a blocking Receive or Send. 118 bool Shutdown(); 119 120 #if defined(OS_WIN) 121 // Since the Linux and Mac implementations actually use a socket, shutting 122 // them down from another thread is pretty simple - we can just call 123 // shutdown(). However, the Windows implementation relies on named pipes 124 // and there isn't a way to cancel a blocking synchronous Read that is 125 // supported on <Vista. So, for Windows only, we override these 126 // SyncSocket methods in order to support shutting down the 'socket'. 127 virtual bool Close() OVERRIDE; 128 virtual size_t Receive(void* buffer, size_t length) OVERRIDE; 129 virtual size_t ReceiveWithTimeout(void* buffer, 130 size_t length, 131 TimeDelta timeout) OVERRIDE; 132 #endif 133 134 // Send() is overridden to catch cases where the remote end is not responding 135 // and we fill the local socket buffer. When the buffer is full, this 136 // implementation of Send() will not block indefinitely as 137 // SyncSocket::Send will, but instead return 0, as no bytes could be sent. 138 // Note that the socket will not be closed in this case. 139 virtual size_t Send(const void* buffer, size_t length) OVERRIDE; 140 141 private: 142 #if defined(OS_WIN) 143 WaitableEvent shutdown_event_; 144 WaitableEvent file_operation_; 145 #endif 146 DISALLOW_COPY_AND_ASSIGN(CancelableSyncSocket); 147 }; 148 149 #if defined(OS_WIN) && !defined(COMPONENT_BUILD) 150 // TODO(cpu): remove this once chrome is split in two dlls. 151 __declspec(selectany) 152 const SyncSocket::Handle SyncSocket::kInvalidHandle = INVALID_HANDLE_VALUE; 153 #endif 154 155 } // namespace base 156 157 #endif // BASE_SYNC_SOCKET_H_ 158
