Brooklyn/userland/interface/vcos/vcos_named_semaphore.h

/*
Copyright (c) 2012, Broadcom Europe Ltd
All rights reserved.

Redistribution and use in source and binary forms, with or without
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      documentation and/or other materials provided with the distribution.
    * Neither the name of the copyright holder nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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*/

/*=============================================================================
VideoCore OS Abstraction Layer - named semaphores
=============================================================================*/

#ifndef VCOS_NAMED_SEMAPHORE_H
#define VCOS_NAMED_SEMAPHORE_H

#ifdef __cplusplus
extern "C" {
#endif

#include "interface/vcos/vcos_types.h"
#include "vcos.h"

/**
 * \file
 *
 * Create a named semaphore, or open an existing one by name.
 *
 */

/** 
  * \brief Create a named semaphore.
  *
  * Semaphores are not re-entrant.
  *
  * @param sem   Pointer to memory to be initialized
  * @param name  A name for this semaphore.
  * @param count The initial count for the semaphore.
  *
  * @return VCOS_SUCCESS if the semaphore was created.
  * 
  */
VCOS_INLINE_DECL
VCOS_STATUS_T vcos_named_semaphore_create(VCOS_NAMED_SEMAPHORE_T *sem, const char *name, VCOS_UNSIGNED count);

/**
  * \brief Wait on a named semaphore.
  *
  * There is no timeout option on a semaphore, as adding this will slow down
  * implementations on some platforms. If you need that kind of behaviour, use
  * an event group.
  *
  * This always returns VCOS_SUCCESS and so should really be a void function. However
  * too many lines of code would need to be changed in non-trivial ways, so for now
  * it is non-void.
  *
  * @param sem Semaphore to wait on
  * @return VCOS_SUCCESS - semaphore was taken.
  *
  */
VCOS_INLINE_DECL
void vcos_named_semaphore_wait(VCOS_NAMED_SEMAPHORE_T *sem);

/**
  * \brief Try to wait for a semaphore.
  *
  * Try to obtain the semaphore. If it is already taken, return VCOS_TIMEOUT.
  * @param sem Semaphore to wait on
  * @return VCOS_SUCCESS - semaphore was taken.
  *         VCOS_EAGAIN - could not take semaphore
  */
VCOS_INLINE_DECL
VCOS_STATUS_T vcos_named_semaphore_trywait(VCOS_NAMED_SEMAPHORE_T *sem);

/**
  * \brief Post a semaphore.
  *
  * @param sem Semaphore to wait on
  */
VCOS_INLINE_DECL
void vcos_named_semaphore_post(VCOS_NAMED_SEMAPHORE_T *sem);

/**
  * \brief Delete a semaphore, releasing any resources consumed by it.
  *
  * @param sem Semaphore to wait on
  */
void vcos_named_semaphore_delete(VCOS_NAMED_SEMAPHORE_T *sem);


#ifdef __cplusplus
}
#endif
#endif