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_ |