1 /* 2 Copyright (c) 2007-2016 Contributors as noted in the AUTHORS file 3 4 This file is part of libzmq, the ZeroMQ core engine in C++. 5 6 libzmq is free software; you can redistribute it and/or modify it under 7 the terms of the GNU Lesser General Public License (LGPL) as published 8 by the Free Software Foundation; either version 3 of the License, or 9 (at your option) any later version. 10 11 As a special exception, the Contributors give you permission to link 12 this library with independent modules to produce an executable, 13 regardless of the license terms of these independent modules, and to 14 copy and distribute the resulting executable under terms of your choice, 15 provided that you also meet, for each linked independent module, the 16 terms and conditions of the license of that module. An independent 17 module is a module which is not derived from or based on this library. 18 If you modify this library, you must extend this exception to your 19 version of the library. 20 21 libzmq is distributed in the hope that it will be useful, but WITHOUT 22 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 23 FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 24 License for more details. 25 26 You should have received a copy of the GNU Lesser General Public License 27 along with this program. If not, see <http://www.gnu.org/licenses/>. 28 */ 29 30 #ifndef __ZMQ_YPIPE_CONFLATE_HPP_INCLUDED__ 31 #define __ZMQ_YPIPE_CONFLATE_HPP_INCLUDED__ 32 33 #include "platform.hpp" 34 #include "dbuffer.hpp" 35 #include "ypipe_base.hpp" 36 37 namespace zmq 38 { 39 // Adapter for dbuffer, to plug it in instead of a queue for the sake 40 // of implementing the conflate socket option, which, if set, makes 41 // the receiving side to discard all incoming messages but the last one. 42 // 43 // reader_awake flag is needed here to mimic ypipe delicate behaviour 44 // around the reader being asleep (see 'c' pointer being NULL in ypipe.hpp) 45 46 template <typename T> class ypipe_conflate_t ZMQ_FINAL : public ypipe_base_t<T> 47 { 48 public: 49 // Initialises the pipe. ypipe_conflate_t()50 ypipe_conflate_t () : reader_awake (false) {} 51 52 // Following function (write) deliberately copies uninitialised data 53 // when used with zmq_msg. Initialising the VSM body for 54 // non-VSM messages won't be good for performance. 55 56 #ifdef ZMQ_HAVE_OPENVMS 57 #pragma message save 58 #pragma message disable(UNINIT) 59 #endif write(const T & value_,bool incomplete_)60 void write (const T &value_, bool incomplete_) 61 { 62 (void) incomplete_; 63 64 dbuffer.write (value_); 65 } 66 67 #ifdef ZMQ_HAVE_OPENVMS 68 #pragma message restore 69 #endif 70 71 // There are no incomplete items for conflate ypipe unwrite(T *)72 bool unwrite (T *) { return false; } 73 74 // Flush is no-op for conflate ypipe. Reader asleep behaviour 75 // is as of the usual ypipe. 76 // Returns false if the reader thread is sleeping. In that case, 77 // caller is obliged to wake the reader up before using the pipe again. flush()78 bool flush () { return reader_awake; } 79 80 // Check whether item is available for reading. check_read()81 bool check_read () 82 { 83 const bool res = dbuffer.check_read (); 84 if (!res) 85 reader_awake = false; 86 87 return res; 88 } 89 90 // Reads an item from the pipe. Returns false if there is no value. 91 // available. read(T * value_)92 bool read (T *value_) 93 { 94 if (!check_read ()) 95 return false; 96 97 return dbuffer.read (value_); 98 } 99 100 // Applies the function fn to the first elemenent in the pipe 101 // and returns the value returned by the fn. 102 // The pipe mustn't be empty or the function crashes. probe(bool (* fn_)(const T &))103 bool probe (bool (*fn_) (const T &)) { return dbuffer.probe (fn_); } 104 105 protected: 106 dbuffer_t<T> dbuffer; 107 bool reader_awake; 108 109 ZMQ_NON_COPYABLE_NOR_MOVABLE (ypipe_conflate_t) 110 }; 111 } 112 113 #endif 114