/usr/include/raul/DoubleBuffer.hpp is in libraul-dev 0.8.0+dfsg0-0.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 | /* This file is part of Raul.
* Copyright (C) 2007-2009 David Robillard <http://drobilla.net>
*
* Raul is free software; you can redistribute it and/or modify it under the
* terms of the GNU General Public License as published by the Free Software
* Foundation; either version 2 of the License, or (at your option) any later
* version.
*
* Raul is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef RAUL_DOUBLE_BUFFER_HPP
#define RAUL_DOUBLE_BUFFER_HPP
#include "raul/AtomicInt.hpp"
#include "raul/AtomicPtr.hpp"
namespace Raul {
/** Double buffer.
*
* Can be thought of as a wrapper class to make a non-atomic type atomically
* settable (with no locking).
*
* Read/Write realtime safe, many writers safe - but set calls may fail.
*
* Space: 2*sizeof(T) + sizeof(int) + sizeof(void*)
* \ingroup raul
*/
template<typename T>
class DoubleBuffer {
public:
inline DoubleBuffer(T val)
: _state(RAUL_DB_READ_WRITE)
{
_vals[0] = val;
_read_val = &_vals[0];
}
inline DoubleBuffer(const DoubleBuffer& copy)
: _state(RAUL_DB_READ_WRITE)
{
T val = copy.get();
_vals[0] = val;
_read_val = &_vals[0];
}
inline T& get() const {
return *_read_val.get();
}
inline bool set(T new_val) {
if (_state.compare_and_exchange(RAUL_DB_READ_WRITE, RAUL_DB_READ_LOCK)) {
// locked _vals[1] for write
_vals[1] = new_val;
_read_val = &_vals[1];
_state = RAUL_DB_WRITE_READ;
return true;
// concurrent calls here are fine. good, actually - caught
// the WRITE_READ state immediately after it was set above
} else if (_state.compare_and_exchange(RAUL_DB_WRITE_READ, RAUL_DB_LOCK_READ)) {
// locked _vals[0] for write
_vals[0] = new_val;
_read_val = &_vals[0];
_state = RAUL_DB_READ_WRITE;
return true;
} else {
return false;
}
}
private:
enum States {
// vals[0] state _ vals[1] state
RAUL_DB_READ_WRITE = 0,
RAUL_DB_READ_LOCK,
RAUL_DB_WRITE_READ,
RAUL_DB_LOCK_READ
};
AtomicInt _state;
AtomicPtr<T> _read_val;
T _vals[2];
};
} // namespace Raul
#endif // RAUL_DOUBLE_BUFFER_HPP
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