/* Copyright 2012 David Robillard Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies. THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #ifndef ZIX_SEM_H #define ZIX_SEM_H #ifdef __APPLE__ # include #elif defined(_WIN32) # include #else # include # include #endif #include "zix/common.h" #ifdef __cplusplus extern "C" { #endif /** @addtogroup zix @{ @name Semaphore @{ */ /** A counting semaphore. This is an integer that is always positive, and has two main operations: increment (post) and decrement (wait). If a decrement can not be performed (i.e. the value is 0) the caller will be blocked until another thread posts and the operation can succeed. Semaphores can be created with any starting value, but typically this will be 0 so the semaphore can be used as a simple signal where each post corresponds to one wait. Semaphores are very efficient (much moreso than a mutex/cond pair). In particular, at least on Linux, post is async-signal-safe, which means it does not block and will not be interrupted. If you need to signal from a realtime thread, this is the most appropriate primitive to use. */ typedef struct ZixSemImpl ZixSem; /** Create and initialize @c sem to @c initial. */ static inline ZixStatus zix_sem_init(ZixSem* sem, unsigned initial); /** Destroy @c sem. */ static inline void zix_sem_destroy(ZixSem* sem); /** Increment (and signal any waiters). Realtime safe. */ static inline void zix_sem_post(ZixSem* sem); /** Wait until count is > 0, then decrement. Obviously not realtime safe. */ static inline ZixStatus zix_sem_wait(ZixSem* sem); /** Non-blocking version of wait(). @return true if decrement was successful (lock was acquired). */ static inline bool zix_sem_try_wait(ZixSem* sem); /** @cond */ #ifdef __APPLE__ struct ZixSemImpl { semaphore_t sem; }; static inline ZixStatus zix_sem_init(ZixSem* sem, unsigned initial) { return semaphore_create(mach_task_self(), &sem->sem, SYNC_POLICY_FIFO, 0) ? ZIX_STATUS_ERROR : ZIX_STATUS_SUCCESS; } static inline void zix_sem_destroy(ZixSem* sem) { semaphore_destroy(mach_task_self(), sem->sem); } static inline void zix_sem_post(ZixSem* sem) { semaphore_signal(sem->sem); } static inline ZixStatus zix_sem_wait(ZixSem* sem) { if (semaphore_wait(sem->sem) != KERN_SUCCESS) { return ZIX_STATUS_ERROR; } return ZIX_STATUS_SUCCESS; } static inline bool zix_sem_try_wait(ZixSem* sem) { const mach_timespec_t zero = { 0, 0 }; return semaphore_timedwait(sem->sem, zero) == KERN_SUCCESS; } #elif defined(_WIN32) struct ZixSemImpl { HANDLE sem; }; static inline ZixStatus zix_sem_init(ZixSem* sem, unsigned initial) { sem->sem = CreateSemaphore(NULL, initial, LONG_MAX, NULL); return (sem->sem) ? ZIX_STATUS_ERROR : ZIX_STATUS_SUCCESS; } static inline void zix_sem_destroy(ZixSem* sem) { CloseHandle(sem->sem); } static inline void zix_sem_post(ZixSem* sem) { ReleaseSemaphore(sem->sem, 1, NULL); } static inline ZixStatus zix_sem_wait(ZixSem* sem) { if (WaitForSingleObject(sem->sem, INFINITE) != WAIT_OBJECT_0) { return ZIX_STATUS_ERROR; } return ZIX_STATUS_SUCCESS; } static inline bool zix_sem_try_wait(ZixSem* sem) { WaitForSingleObject(sem->sem, 0); } #else /* !defined(__APPLE__) && !defined(_WIN32) */ struct ZixSemImpl { sem_t sem; }; static inline ZixStatus zix_sem_init(ZixSem* sem, unsigned initial) { return sem_init(&sem->sem, 0, initial) ? ZIX_STATUS_ERROR : ZIX_STATUS_SUCCESS; } static inline void zix_sem_destroy(ZixSem* sem) { sem_destroy(&sem->sem); } static inline void zix_sem_post(ZixSem* sem) { sem_post(&sem->sem); } static inline ZixStatus zix_sem_wait(ZixSem* sem) { while (sem_wait(&sem->sem)) { if (errno != EINTR) { return ZIX_STATUS_ERROR; } /* Otherwise, interrupted, so try again. */ } return ZIX_STATUS_SUCCESS; } static inline bool zix_sem_try_wait(ZixSem* sem) { return (sem_trywait(&sem->sem) == 0); } #endif /** @endcond @} @} */ #ifdef __cplusplus } /* extern "C" */ #endif #endif /* ZIX_SEM_H */ 8'>78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168