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