esp-idf/components/pthread/include/semaphore.h

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/*
* SPDX-FileCopyrightText: 2023 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
#pragma once
#include <time.h>
#ifdef __cplusplus
extern "C" {
#endif
typedef unsigned int sem_t;
/**
* This is the maximum value to which any POSIX semaphore can count on ESP chips.
*/
#define SEM_VALUE_MAX 0x7FFF
/**
* This is a POSIX function, please refer to the POSIX specification for a detailed description.
*
* Must NOT be called if threads are still blocked on semaphore!
*/
int sem_destroy(sem_t *sem);
/**
* This is a POSIX function, please refer to the POSIX specification for a detailed description.
*
* Note that on ESP chips, pshared is ignored. Semaphores can always be shared between FreeRTOS tasks.
*/
int sem_init(sem_t *sem, int pshared, unsigned value);
/**
* This is a POSIX function, please refer to the POSIX specification for a detailed description.
*
* Note that, unlike specified in POSIX, this implementation returns -1 and sets errno to
* EAGAIN if the semaphore can not be unlocked (posted) due to its value being SEM_VALUE_MAX.
*/
int sem_post(sem_t *sem);
/**
* This is a POSIX function, please refer to the POSIX specification for a detailed description.
*
* Note the following three deviations/issues originating from the underlying FreeRTOS implementation:
* * The time value passed by abstime will be rounded up to the next FreeRTOS tick.
* * The actual timeout will happen after the tick the time was rounded to
* and before the following tick.
* * It is possible, though unlikely, that the task is preempted directly after the timeout calculation,
* delaying timeout of the following blocking operating system call by the duration of the preemption.
*/
int sem_timedwait(sem_t * restrict semaphore, const struct timespec *restrict abstime);
/**
* This is a POSIX function, please refer to the POSIX specification for a detailed description.
*/
int sem_trywait(sem_t *sem);
/**
* This is a POSIX function, please refer to the POSIX specification for a detailed description.
*/
int sem_wait(sem_t *sem);
/**
* This is a POSIX function, please refer to the POSIX specification for a detailed description.
*/
int sem_getvalue(sem_t *restrict sem, int *restrict sval);
#ifdef __cplusplus
}
#endif