DoubleBuffer.hpp
/* 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 {
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
Raul::AtomicPtr
Atomic pointer.
Definition: AtomicPtr.hpp:30
Raul
Definition: Array.hpp:26
Raul::DoubleBuffer
Double buffer.
Definition: DoubleBuffer.hpp:37
Raul::AtomicInt::compare_and_exchange
bool compare_and_exchange(int old, int val)
Set value to val iff current value is old.
Definition: AtomicInt.hpp:64
Raul::AtomicInt
Atomic integer.
Definition: AtomicInt.hpp:29