amt630hv160-sdk-release/amt630hv160-freertos-beta/FreeRTOS-Plus/FreeRTOS-Plus-POSIX/include/FreeRTOS_POSIX/semaphore.h

/*
 * 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_ */