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/*
* Amazon FreeRTOS POSIX V1.1.0
* Copyright (C) 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* http://aws.amazon.com/freertos
* http://www.FreeRTOS.org
*/
/**
* @file semaphore.h
* @brief Semaphores.
*
* http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/semaphore.h.html
*/
#ifndef _FREERTOS_POSIX_SEMAPHORE_H_
#define _FREERTOS_POSIX_SEMAPHORE_H_
/* FreeRTOS+POSIX includes. */
#include "FreeRTOS_POSIX/time.h"
#include "FreeRTOS_POSIX_types.h"
/**
* @brief Semaphore type.
*/
typedef PosixSemType_t sem_t;
/**
* @brief Destroy an unnamed semaphore.
*
* @see http://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_destroy.html
*
* @retval 0 - upon successful completion
*
* @note Semaphore is destroyed regardless of whether there is any thread currently blocked on this semaphore.
*/
int sem_destroy( sem_t * sem );
/**
* @brief Get the value of a semaphore.
*
* @see http://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_getvalue.html
*
* @retval 0 - Upon successful completion
*
* @note If sem is locked, then the object to which sval points is set to zero.
*/
int sem_getvalue( sem_t * sem,
int * sval );
/**
* @brief Initialize an unnamed semaphore.
*
* @see http://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_init.html
*
* @note pshared is ignored. Semaphores will always be considered "shared".
*
* @retval 0 - upon successful completion
* @retval -1 - otherwise. System error variable errno is also set in this case.
*
* @sideeffect Possible errno values
* <br>
* EINVAL - The value argument exceeds {SEM_VALUE_MAX}.
* <br>
* ENOSPC - A resource required to initialize the semaphore has been exhausted.
*/
int sem_init( sem_t * sem,
int pshared,
unsigned value );
/**
* @brief Unlock a semaphore.
*
* @see http://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_post.html
*
* @retval 0 - upon successful completion
*/
int sem_post( sem_t * sem );
/**
* @brief Lock a semaphore with timeout.
*
* @see http://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_timedwait.html
*
* @retval 0 - upon successful completion
* @retval -1 - otherwise. System error variable errno is also set in this case.
*
* @sideeffect Possible errno values
* <br>
* EINVAL - parameter specified a nanoseconds field value less than zero or greater
* than or equal to 1000 million
* <br>
* ETIMEDOUT - The semaphore could not be locked before the specified timeout expired.
*
* @note Deadlock detection is not implemented.
*/
int sem_timedwait( sem_t * sem,
const struct timespec * abstime );
/**
* @brief Lock a semaphore if available.
*
* @see http://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_trywait.html
*
* @retval 0 - upon successful completion
* @retval -1 - otherwise. System error variable errno is also set in this case.
*
* @sideeffect Possible errno values
* <br>
* EAGAIN - The semaphore was already locked, so it cannot be immediately locked by the sem_trywait() operation.
*/
int sem_trywait( sem_t * sem );
/**
* @brief Lock a semaphore.
*
* @see http://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_wait.html
*
* @retval 0 - upon successful completion
* @retval -1 - otherwise. System error variable errno is also set in this case.
*
* @note Deadlock detection is not implemented.
*/
int sem_wait( sem_t * sem );
#endif /* ifndef _FREERTOS_POSIX_SEMAPHORE_H_ */
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