ardupilot/libraries/AP_Common/Semaphore.h

55 lines
1.8 KiB
C++

/*
This program 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 3 of the License, or
(at your option) any later version.
This program 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 more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
/*
a method to make semaphores less error prone. The WITH_SEMAPHORE()
macro will block forever for a semaphore, and will automatically
release the semaphore when it goes out of scope
Note that we have two types of semaphores. A normal semaphore can
only be taken once. A recursive semaphore allows for the thread
holding the semaphore to take it again. It must be released the same
number of times it is taken.
The WITH_SEMAPHORE() macro can be used with either type of semaphore
*/
#include <AP_HAL/Semaphores.h>
namespace AP_HAL {
class Semaphore;
}
class WithSemaphore {
public:
WithSemaphore(AP_HAL::Semaphore *mtx) : WithSemaphore(*mtx) { }
WithSemaphore(AP_HAL::Semaphore &mtx) : _mtx(mtx) {
_mtx.take_blocking();
}
~WithSemaphore() {
_mtx.give();
}
private:
AP_HAL::Semaphore &_mtx;
};
// From: https://stackoverflow.com/questions/19666142/why-is-a-level-of-indirection-needed-for-this-concatenation-macro
#define WITH_SEMAPHORE( sem ) JOIN( sem, __COUNTER__ )
#define JOIN( symbol1, symbol2 ) _DO_JOIN( symbol1, symbol2 )
#define _DO_JOIN( symbol1, symbol2 ) WithSemaphore _getsem ## symbol2(symbol1)