diff --git a/tasks/SemaphoreFactory.h b/tasks/SemaphoreFactory.h new file mode 100644 index 000000000..7f8edaf12 --- /dev/null +++ b/tasks/SemaphoreFactory.h @@ -0,0 +1,49 @@ +#ifndef FRAMEWORK_TASKS_SEMAPHOREFACTORY_H_ +#define FRAMEWORK_TASKS_SEMAPHOREFACTORY_H_ +#include + +/** + * Creates Semaphore. + * This class is a "singleton" interface, i.e. it provides an + * interface, but also is the base class for a singleton. + */ +class SemaphoreFactory { +public: + virtual ~SemaphoreFactory(); + /** + * Returns the single instance of SemaphoreFactory. + * The implementation of #instance is found in its subclasses. + * Thus, we choose link-time variability of the instance. + */ + static SemaphoreFactory* instance(); + + /** + * Create a binary semaphore. + * Creator function for a binary semaphore which may only be acquired once + * @param argument Can be used to pass implementation specific information. + * @return Pointer to newly created semaphore class instance. + */ + SemaphoreIF* createBinarySemaphore(uint32_t arguments = 0); + /** + * Create a counting semaphore. + * Creator functons for a counting semaphore which may be acquired multiple + * times. + * @param count Semaphore can be taken count times. + * @param initCount Initial count value. + * @param argument Can be used to pass implementation specific information. + * @return + */ + SemaphoreIF* createCountingSemaphore(const uint8_t maxCount, + uint8_t initCount, uint32_t arguments = 0); + + void deleteSemaphore(SemaphoreIF* semaphore); + +private: + /** + * External instantiation is not allowed. + */ + SemaphoreFactory(); + static SemaphoreFactory* factoryInstance; +}; + +#endif /* FRAMEWORK_TASKS_SEMAPHOREFACTORY_H_ */ diff --git a/tasks/SemaphoreIF.h b/tasks/SemaphoreIF.h new file mode 100644 index 000000000..a7c5a97b9 --- /dev/null +++ b/tasks/SemaphoreIF.h @@ -0,0 +1,61 @@ +#ifndef FRAMEWORK_TASKS_SEMAPHOREIF_H_ +#define FRAMEWORK_TASKS_SEMAPHOREIF_H_ +#include +#include +#include + +/** + * @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_ */