RAUL 0.7.0
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00001 /* This file is part of Raul. 00002 * Copyright (C) 2007-2009 David Robillard <http://drobilla.net> 00003 * 00004 * Raul is free software; you can redistribute it and/or modify it under the 00005 * terms of the GNU General Public License as published by the Free Software 00006 * Foundation; either version 2 of the License, or (at your option) any later 00007 * version. 00008 * 00009 * Raul is distributed in the hope that it will be useful, but WITHOUT ANY 00010 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 00011 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for details. 00012 * 00013 * You should have received a copy of the GNU General Public License along 00014 * with this program; if not, write to the Free Software Foundation, Inc., 00015 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 00016 */ 00017 00018 #ifndef RAUL_DOUBLE_BUFFER_HPP 00019 #define RAUL_DOUBLE_BUFFER_HPP 00020 00021 #include "raul/AtomicInt.hpp" 00022 #include "raul/AtomicPtr.hpp" 00023 00024 namespace Raul { 00025 00035 template<typename T> 00036 class DoubleBuffer { 00037 public: 00038 00039 inline DoubleBuffer(T val) 00040 : _state(RAUL_DB_READ_WRITE) 00041 { 00042 _vals[0] = val; 00043 _read_val = &_vals[0]; 00044 } 00045 00046 inline DoubleBuffer(const DoubleBuffer& copy) 00047 : _state(RAUL_DB_READ_WRITE) 00048 { 00049 T val = copy.get(); 00050 _vals[0] = val; 00051 _read_val = &_vals[0]; 00052 } 00053 00054 inline T& get() const { 00055 return *_read_val.get(); 00056 } 00057 00058 inline bool set(T new_val) { 00059 if (_state.compare_and_exchange(RAUL_DB_READ_WRITE, RAUL_DB_READ_LOCK)) { 00060 00061 // locked _vals[1] for write 00062 _vals[1] = new_val; 00063 _read_val = &_vals[1]; 00064 _state = RAUL_DB_WRITE_READ; 00065 return true; 00066 00067 // concurrent calls here are fine. good, actually - caught 00068 // the WRITE_READ state immediately after it was set above 00069 00070 } else if (_state.compare_and_exchange(RAUL_DB_WRITE_READ, RAUL_DB_LOCK_READ)) { 00071 00072 // locked _vals[0] for write 00073 _vals[0] = new_val; 00074 _read_val = &_vals[0]; 00075 _state = RAUL_DB_READ_WRITE; 00076 return true; 00077 00078 } else { 00079 00080 return false; 00081 00082 } 00083 } 00084 00085 private: 00086 enum States { 00087 // vals[0] state _ vals[1] state 00088 RAUL_DB_READ_WRITE = 0, 00089 RAUL_DB_READ_LOCK, 00090 RAUL_DB_WRITE_READ, 00091 RAUL_DB_LOCK_READ 00092 }; 00093 00094 AtomicInt _state; 00095 AtomicPtr<T> _read_val; 00096 T _vals[2]; 00097 }; 00098 00099 00100 } // namespace Raul 00101 00102 #endif // RAUL_DOUBLE_BUFFER_HPP