/************************************************************
* lib_sem.c
*
* Copyright (C) 2007 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name Gregory Nutt 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 DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
************************************************************/
/************************************************************
* Included Files
************************************************************/
#include <nuttx/config.h>
#ifdef CONFIG_STDIO_BUFFERED_IO
#include <unistd.h>
#include <semaphore.h>
#include <errno.h>
#include <assert.h>
#include "lib_internal.h"
/************************************************************
* Definitions
************************************************************/
/************************************************************
* Private Data
************************************************************/
/************************************************************
* Global Functions
************************************************************/
/************************************************************
* lib_sem_initialize
************************************************************/
void lib_sem_initialize(FILE *stream)
{
/* Initialize the LIB semaphore to one (to support one-at-
* a-time access to private data sets.
*/
(void)sem_init(&stream->sem, 0, 1);
stream->holder = -1;
stream->counts = 0;
}
/************************************************************
* lib_take_semaphore
************************************************************/
void lib_take_semaphore(FILE *stream)
{
pid_t my_pid = getpid();
/* Do I already have the semaphore? */
if (stream->holder == my_pid)
{
/* Yes, just increment the number of references that I have */
stream->counts++;
}
else
{
/* Take the semaphore (perhaps waiting) */
while (sem_wait(&stream->sem) != 0)
{
/* The only case that an error should occr here is if
* the wait was awakened by a signal.
*/
ASSERT(*get_errno_ptr() == EINTR);
}
/* We have it. Stake the claim and return */
stream->holder = my_pid;
stream->counts = 1;
}
}
/************************************************************
* lib_give_semaphore
************************************************************/
void lib_give_semaphore(FILE *stream)
{
pid_t my_pid = getpid();
/* I better be holding at least one count on the semaphore */
ASSERT(stream->holder == my_pid);
/* Do I hold multiple references to the semphore */
if (stream->counts > 1)
{
/* Yes, just release one count and return */
stream->counts--;
}
else
{
/* Nope, this is the last reference I have */
stream->holder = -1;
stream->counts = 0;
ASSERT(sem_post(&stream->sem) == 0);
}
}
#endif /* CONFIG_STDIO_BUFFERED_IO */
