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 <stddef.h> 13 14 #include "base/base_export.h" 15 #include "base/compiler_specific.h" 16 #include "base/macros.h" 17 #include "base/process/process_handle.h" 18 #include "base/synchronization/waitable_event.h" 19 #include "base/time/time.h" 20 #include "build/build_config.h" 21 22 #if defined(OS_WIN) 23 #include <windows.h> 24 #endif 25 #include <sys/types.h> 26 27 #if defined(OS_POSIX) 28 #include "base/file_descriptor_posix.h" 29 #endif 30 31 namespace base { 32 33 class BASE_EXPORT SyncSocket { 34 public: 35 #if defined(OS_WIN) 36 typedef HANDLE Handle; 37 typedef Handle TransitDescriptor; 38 #else 39 typedef int Handle; 40 typedef FileDescriptor TransitDescriptor; 41 #endif 42 static const Handle kInvalidHandle; 43 44 SyncSocket(); 45 46 // Creates a SyncSocket from a Handle. Used in transport. 47 explicit SyncSocket(Handle handle) : handle_(handle) {} 48 virtual ~SyncSocket(); 49 50 // Initializes and connects a pair of sockets. 51 // |socket_a| and |socket_b| must not hold a valid handle. Upon successful 52 // return, the sockets will both be valid and connected. 53 static bool CreatePair(SyncSocket* socket_a, SyncSocket* socket_b); 54 55 // Returns |Handle| wrapped in a |TransitDescriptor|. 56 static Handle UnwrapHandle(const TransitDescriptor& descriptor); 57 58 // Prepares a |TransitDescriptor| which wraps |Handle| used for transit. 59 // This is used to prepare the underlying shared resource before passing back 60 // the handle to be used by the peer process. 61 bool PrepareTransitDescriptor(ProcessHandle peer_process_handle, 62 TransitDescriptor* descriptor); 63 64 // Closes the SyncSocket. Returns true on success, false on failure. 65 virtual bool Close(); 66 67 // Sends the message to the remote peer of the SyncSocket. 68 // Note it is not safe to send messages from the same socket handle by 69 // multiple threads simultaneously. 70 // buffer is a pointer to the data to send. 71 // length is the length of the data to send (must be non-zero). 72 // Returns the number of bytes sent, or 0 upon failure. 73 virtual size_t Send(const void* buffer, size_t length); 74 75 // Receives a message from an SyncSocket. 76 // buffer is a pointer to the buffer to receive data. 77 // length is the number of bytes of data to receive (must be non-zero). 78 // Returns the number of bytes received, or 0 upon failure. 79 virtual size_t Receive(void* buffer, size_t length); 80 81 // Same as Receive() but only blocks for data until |timeout| has elapsed or 82 // |buffer| |length| is exhausted. Currently only timeouts less than one 83 // second are allowed. Return the amount of data read. 84 virtual size_t ReceiveWithTimeout(void* buffer, 85 size_t length, 86 TimeDelta timeout); 87 88 // Returns the number of bytes available. If non-zero, Receive() will not 89 // not block when called. 90 virtual size_t Peek(); 91 92 // Extracts the contained handle. Used for transferring between 93 // processes. 94 Handle handle() const { return handle_; } 95 96 protected: 97 Handle handle_; 98 99 private: 100 DISALLOW_COPY_AND_ASSIGN(SyncSocket); 101 }; 102 103 // Derives from SyncSocket and adds support for shutting down the socket from 104 // another thread while a blocking Receive or Send is being done from the 105 // thread that owns the socket. 106 class BASE_EXPORT CancelableSyncSocket : public SyncSocket { 107 public: 108 CancelableSyncSocket(); 109 explicit CancelableSyncSocket(Handle handle); 110 ~CancelableSyncSocket() override {} 111 112 // Initializes a pair of cancelable sockets. See documentation for 113 // SyncSocket::CreatePair for more details. 114 static bool CreatePair(CancelableSyncSocket* socket_a, 115 CancelableSyncSocket* socket_b); 116 117 // A way to shut down a socket even if another thread is currently performing 118 // a blocking Receive or Send. 119 bool Shutdown(); 120 121 #if defined(OS_WIN) 122 // Since the Linux and Mac implementations actually use a socket, shutting 123 // them down from another thread is pretty simple - we can just call 124 // shutdown(). However, the Windows implementation relies on named pipes 125 // and there isn't a way to cancel a blocking synchronous Read that is 126 // supported on <Vista. So, for Windows only, we override these 127 // SyncSocket methods in order to support shutting down the 'socket'. 128 bool Close() override; 129 size_t Receive(void* buffer, size_t length) override; 130 size_t ReceiveWithTimeout(void* buffer, 131 size_t length, 132 TimeDelta timeout) override; 133 #endif 134 135 // Send() is overridden to catch cases where the remote end is not responding 136 // and we fill the local socket buffer. When the buffer is full, this 137 // implementation of Send() will not block indefinitely as 138 // SyncSocket::Send will, but instead return 0, as no bytes could be sent. 139 // Note that the socket will not be closed in this case. 140 size_t Send(const void* buffer, size_t length) override; 141 142 private: 143 #if defined(OS_WIN) 144 WaitableEvent shutdown_event_; 145 WaitableEvent file_operation_; 146 #endif 147 DISALLOW_COPY_AND_ASSIGN(CancelableSyncSocket); 148 }; 149 150 #if defined(OS_WIN) && !defined(COMPONENT_BUILD) 151 // TODO(cpu): remove this once chrome is split in two dlls. 152 __declspec(selectany) 153 const SyncSocket::Handle SyncSocket::kInvalidHandle = INVALID_HANDLE_VALUE; 154 #endif 155 156 } // namespace base 157 158 #endif // BASE_SYNC_SOCKET_H_ 159
