amiro-os / include / amiro / util / rwlock.hpp @ 58fe0e0b
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| 1 | 58fe0e0b | Thomas Schöpping | #ifndef AMIRO_RWLOCK_H_
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| 2 | #define AMIRO_RWLOCK_H_
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| 3 | |||
| 4 | #include <ch.hpp> |
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| 5 | |||
| 6 | namespace amiro {
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| 7 | |||
| 8 | /**
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| 9 | * @brief An enhanced mutex with parallel read but exclusive write capabilities
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| 10 | */
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| 11 | class RWLock |
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| 12 | {
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| 13 | public:
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| 14 | /**
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| 15 | * @brief An enum to specify the favoritism of the RWLock
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| 16 | */
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| 17 | enum Favor : bool { |
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| 18 | FAVOR_READERS = false, /**< Favors readers, even if writers are waiting */ |
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| 19 | FAVOR_WRITERS = true, /**< Favors writers and holds new readers back */ |
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| 20 | }; |
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| 21 | |||
| 22 | /**
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| 23 | * @brief An enum to specify what to wait for in the tryLockReading() and tryLockWriting() methods.
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| 24 | */
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| 25 | enum WaitingType : uint8_t {
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| 26 | WAIT_FOR_NONE = 0, /**< does not block at all */ |
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| 27 | WAIT_FOR_MUTEX = 1, /**< blocks at the mutex */ |
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| 28 | WAIT_FOR_QUEUE = 2, /**< waits for the queues */ |
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| 29 | }; |
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| 30 | |||
| 31 | private:
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| 32 | /**
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| 33 | * @brief A status struct holding the current configuration of the RWLock.
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| 34 | */
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| 35 | struct AccessStatus {
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| 36 | uint8_t reader_count : 7; /**< The number of currently active readers (128 max) */ |
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| 37 | uint8_t favor : 1; /**< The currently selected favoritism */ |
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| 38 | }; |
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| 39 | |||
| 40 | chibios_rt::Mutex mutex; /**< A mutex lock used for synchronization */
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| 41 | chibios_rt::CondVar waiting_readers; /**< A condition variable for waiting readers */
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| 42 | chibios_rt::CondVar waiting_writers; /**< A condition variable for all waiting writers */
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| 43 | AccessStatus status; /**< The current status of the RWLock */
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| 44 | |||
| 45 | public:
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| 46 | /**
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| 47 | * @brief Constructor of the RWLock class.
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| 48 | * @param[in] favor The initial favoritism (default: FAVOR_WRITERS)
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| 49 | */
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| 50 | explicit RWLock(const Favor favor = FAVOR_WRITERS); |
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| 51 | |||
| 52 | /**
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| 53 | * @brief Destructor of the RWLock class.
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| 54 | */
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| 55 | virtual ~RWLock();
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| 56 | |||
| 57 | /**
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| 58 | * @brief Lock the RWLock as a reader (shared mode)
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| 59 | */
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| 60 | void lockReading();
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| 61 | |||
| 62 | /**
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| 63 | * @brief Lock the RWLock as a writer (exclusive mode)
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| 64 | */
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| 65 | void lockWriting();
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| 66 | |||
| 67 | /**
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| 68 | * @brief Try to lock the RWLock as a reader (shared mode) but do not block
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| 69 | * @param[in] wait Can be used to wait for the mutex to lock or the queue to be empty
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| 70 | * @return True if the RWLock was successfully locked; False if not
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| 71 | */
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| 72 | bool tryLockReading(const WaitingType wait = WAIT_FOR_NONE); |
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| 73 | |||
| 74 | /**
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| 75 | * @brief Try to lock the RWLock as a writer (exclusive mode) but do not block
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| 76 | * @param[in] wait Can be used to wait for the mutex to lock or the queue to be empty
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| 77 | * @return True if the RWLock was successfully locked; False if not
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| 78 | */
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| 79 | bool tryLockWriting(const WaitingType wait = WAIT_FOR_NONE); |
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| 80 | |||
| 81 | /**
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| 82 | * @brief Unlocks the RWLock.
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| 83 | * If it was locked in shared or exclusive mode is detected automatically.
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| 84 | */
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| 85 | void unlock();
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| 86 | |||
| 87 | /**
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| 88 | * @brief Set the favoritism of the RWLock
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| 89 | * @param[in] favor Either FAVOR_READERS or FAVOR_WRITERS
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| 90 | */
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| 91 | void setFavoritism(const Favor favor); |
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| 92 | |||
| 93 | /**
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| 94 | * @brief Try to set the favoritism of the RWLock but do not block
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| 95 | * @param[in] favor Either FAVOR_READERS or FAVOR_WRITERS
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| 96 | * @return True if the favoritism was successfully set; False if not
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| 97 | */
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| 98 | bool trySetFavoritism(const Favor favor); |
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| 99 | |||
| 100 | }; |
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| 101 | |||
| 102 | } // end of namespace amiro
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| 103 | |||
| 104 | #endif // AMIRO_RWLOCK_H_ |