fsfw/tasks/SemaphoreIF.h

62 lines
2.4 KiB
C
Raw Normal View History

2020-05-29 13:29:29 +02:00
#ifndef FRAMEWORK_TASKS_SEMAPHOREIF_H_
#define FRAMEWORK_TASKS_SEMAPHOREIF_H_
#include <framework/returnvalues/FwClassIds.h>
#include <framework/returnvalues/HasReturnvaluesIF.h>
#include <cstdint>
/**
* @brief Generic interface for semaphores, which can be used to achieve
* task synchronization. This is a generic interface which can be
* used for both binary semaphores and counting semaphores.
* @details
* A semaphore is a synchronization primitive.
* See: https://en.wikipedia.org/wiki/Semaphore_(programming)
* A semaphore can be used to achieve task synchonization and track the
* availability of resources by using either the binary or the counting
* semaphore types.
*
* If mutual exlcusion of a resource is desired, a mutex should be used,
* which is a special form of a semaphore and has an own interface.
*/
class SemaphoreIF {
public:
virtual~ SemaphoreIF() {};
//! Needs to be defined in implementation. No blocking time
static const uint32_t NO_TIMEOUT;
//! Needs to be defined in implementation. Blocks indefinitely.
static const uint32_t MAX_TIMEOUT;
static const uint8_t INTERFACE_ID = CLASS_ID::SEMAPHORE_IF;
//! Semaphore timeout
static constexpr ReturnValue_t SEMAPHORE_TIMEOUT = MAKE_RETURN_CODE(1);
//! The current semaphore can not be given, because it is not owned
static constexpr ReturnValue_t SEMAPHORE_NOT_OWNED = MAKE_RETURN_CODE(2);
static constexpr ReturnValue_t SEMAPHORE_INVALID = MAKE_RETURN_CODE(3);
/**
* Generic call to acquire a semaphore.
* If there are no more semaphores to be taken (for a counting semaphore,
* a semaphore may be taken more than once), the taks will block
* for a maximum of timeoutMs while trying to acquire the semaphore.
* This can be used to achieve task synchrnization.
* @param timeoutMs
* @return - c RETURN_OK for successfull acquisition
*/
virtual ReturnValue_t acquire(uint32_t timeoutMs) = 0;
/**
* Corrensponding call to release a semaphore.
* @return -@c RETURN_OK for successfull release
*/
virtual ReturnValue_t release() = 0;
/**
* If the semaphore is a counting semaphore then the semaphores current
* count value is returned. If the semaphore is a binary semaphore then 1
* is returned if the semaphore is available, and 0 is returned if the
* semaphore is not available.
*/
virtual uint8_t getSemaphoreCounter() const = 0;
};
#endif /* FRAMEWORK_TASKS_SEMAPHOREIF_H_ */