path: root/semaphore.c

/*
 * -------------------------------------------------------------
 *
 * Module: semaphore.c
 *
 * Purpose:
 *      Semaphores aren't actually part of the PThreads standard.
 *      They are defined by the POSIX Standard:
 *
 *              POSIX 1003.1b-1993      (POSIX.1b)
 *
 * Contents:
 *              Public Methods                    Author
 *              --------------                    ------
 *              sem_init                          John E. Bossom  Mar 1998
 *              sem_destroy                       John E. Bossom  Mar 1998
 *              sem_trywait                       John E. Bossom  Mar 1998
 *              sem_wait                          John E. Bossom  Mar 1998
 *              sem_post                          John E. Bossom  Mar 1998
 *
 *              Private Methods
 *              ---------------
 *
 * -------------------------------------------------------------
 *
 * Pthreads-win32 - POSIX Threads Library for Win32
 * Copyright (C) 1998
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA
 */

#include <windows.h>
//#include <process.h>
//#include <sys/timeb.h>
#include <string.h>

#include "pthread.h"
#include "semaphore.h"

int
sem_init (sem_t * sem, int pshared, unsigned int value)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      This function initializes an unnamed semaphore. the
      *      initial value of the semaphore is 'value'
      *
      * PARAMETERS
      *      sem
      *              pointer to an instance of sem_t
      *
      *      pshared
      *              if zero, this semaphore may only be shared between
      *              threads in the same process.
      *              if nonzero, the semaphore can be shared between
      *              processes
      *
      *      value
      *              initial value of the semaphore counter
      *
      * DESCRIPTION
      *      This function initializes an unnamed semaphore. The
      *      initial value of the semaphore is set to 'value'.
      *
      * RESULTS
      *              0               successfully created semaphore,
      *              -1              failed, error in errno
      * ERRNO
      *              EINVAL          'sem' is not a valid semaphore,
      *              ENOSPC          a required resource has been exhausted,
      *              ENOSYS          semaphores are not supported,
      *              EPERM           the process lacks appropriate privilege
      *
      * ------------------------------------------------------
      */
{
  int result = 0;


  if (pshared != 0)
    {
      /*
       * Creating a semaphore that can be shared between
       * processes
       */
      result = EPERM;

    }
  else
    {

#ifdef NEED_SEM

      sem->value = value;
      pthread_mutex_init(&sem->mutex, NULL);
      sem->event = CreateEvent (NULL,
				FALSE,	/* manual reset */
				FALSE,	/* initial state */
				NULL);
      if (value != 0)
        {
	  SetEvent(sem->event);
        }

#else /* NEED_SEM */

      /*
       * NOTE: Taking advantage of the fact that
       *               sem_t is a simple structure with one entry;
       *               We don't have to allocate it...
       */
      *sem = CreateSemaphore (
			       0,
			       value,
			       0x7FFFFFF,
			       NULL);

      if (*sem == 0)
	{
	  result = ENOSPC;
	}

#endif /* NEED_SEM */

    }

  if (result != 0)
    {
      errno = result;
      return -1;
    }

  return 0;

}				/* sem_init */


int
sem_destroy (sem_t * sem)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      This function destroys an unnamed semaphore.
      *
      * PARAMETERS
      *      sem
      *              pointer to an instance of sem_t
      *
      * DESCRIPTION
      *      This function destroys an unnamed semaphore.
      *
      * RESULTS
      *              0               successfully destroyed semaphore,
      *              -1              failed, error in errno
      * ERRNO
      *              EINVAL          'sem' is not a valid semaphore,
      *              ENOSYS          semaphores are not supported,
      *              EBUSY           threads (or processes) are currently
      *                                      blocked on 'sem'
      *
      * ------------------------------------------------------
      */
{
  int result = 0;

  if (sem == NULL)
    {
      result = EINVAL;
    }

#ifdef NEED_SEM

  else
    {
      pthread_mutex_destroy(&sem->mutex);
      if (!CloseHandle(sem->event))
        {
          result = EINVAL;
        }
    }

#else /* NEED_SEM */

  else if (! CloseHandle (*sem))
    {
      result = EINVAL;
    }

#endif /* NEED_SEM */

  if (result != 0)
    {
      errno = result;
      return -1;
    }

  return 0;

}				/* sem_destroy */


int
sem_trywait (sem_t * sem)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      This function tries to wait on a semaphore.
      *
      * PARAMETERS
      *      sem
      *              pointer to an instance of sem_t
      *
      * DESCRIPTION
      *      This function tries to wait on a semaphore. If the
      *      semaphore value is greater than zero, it decreases
      *      its value by one. If the semaphore value is zero, then
      *      this function returns immediately with the error EAGAIN
      *
      * RESULTS
      *              0               successfully decreased semaphore,
      *              -1              failed, error in errno
      * ERRNO
      *              EAGAIN          the semaphore was already locked,
      *              EINVAL          'sem' is not a valid semaphore,
      *              ENOSYS          semaphores are not supported,
      *              EINTR           the function was interrupted by a signal,
      *              EDEADLK         a deadlock condition was detected.
      *
      * ------------------------------------------------------
      */
{
  int result = 0;

  if (sem == NULL)
    {
      result = EINVAL;
    }

#ifdef NEED_SEM

  /* not yet implemented! */
  result = EINVAL;
  return -1;

#else /* NEED_SEM */

  else if (WaitForSingleObject (*sem, 0) == WAIT_TIMEOUT)
    {
      result = EAGAIN;
    }

#endif /* NEED_SEM */

  if (result != 0)
    {
      errno = result;
      return -1;
    }

  return 0;

}				/* sem_trywait */


#ifdef NEED_SEM

void 
ptw32_decrease_semaphore(sem_t * sem)
{
  pthread_mutex_lock(&sem->mutex);

  if (sem->value != 0)
    {
      sem->value--;
      if (sem->value != 0)
        {
          SetEvent(sem->event);
        }
    }
  else
    {
      /* this case should not happen! */
    }

  pthread_mutex_unlock(&sem->mutex);
}

BOOL 
ptw32_increase_semaphore(sem_t * sem, unsigned int n)
{
  BOOL result;

  pthread_mutex_lock(&sem->mutex);

  if (sem->value + n > sem->value)
    {
       sem->value += n;
       SetEvent(sem->event);
       result = TRUE;
    }
  else
    {
       result = FALSE;
    }

  pthread_mutex_unlock(&sem->mutex);
  return result;
}

#endif /* NEED_SEM */

int
sem_wait (sem_t * sem)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      This function  waits on a semaphore.
      *
      * PARAMETERS
      *      sem
      *              pointer to an instance of sem_t
      *
      * DESCRIPTION
      *      This function waits on a semaphore. If the
      *      semaphore value is greater than zero, it decreases
      *      its value by one. If the semaphore value is zero, then
      *      the calling thread (or process) is blocked until it can
      *      successfully decrease the value or until interrupted by
      *      a signal.
      *
      * RESULTS
      *              0               successfully decreased semaphore,
      *              -1              failed, error in errno
      * ERRNO
      *              EINVAL          'sem' is not a valid semaphore,
      *              ENOSYS          semaphores are not supported,
      *              EINTR           the function was interrupted by a signal,
      *              EDEADLK         a deadlock condition was detected.
      *
      * ------------------------------------------------------
      */
{
  int result = 0;

  if (sem == NULL)
    {
      result = EINVAL;
    }
  else
    {

#ifdef NEED_SEM

	result = pthreadCancelableWait (sem->event);

#else /* NEED_SEM */

	result = pthreadCancelableWait (*sem);

#endif /* NEED_SEM */

    }

  if (result != 0)
    {
      errno = result;
      return -1;
    }

#ifdef NEED_SEM

  ptw32_decrease_semaphore(sem);

#endif /* NEED_SEM */

  return 0;

}				/* sem_wait */


int
sem_post (sem_t * sem)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      This function posts a wakeup to a semaphore.
      *
      * PARAMETERS
      *      sem
      *              pointer to an instance of sem_t
      *
      * DESCRIPTION
      *      This function posts a wakeup to a semaphore. If there
      *      are waiting threads (or processes), one is awakened;
      *      otherwise, the semaphore value is incremented by one.
      *
      * RESULTS
      *              0               successfully posted semaphore,
      *              -1              failed, error in errno
      * ERRNO
      *              EINVAL          'sem' is not a valid semaphore,
      *              ENOSYS          semaphores are not supported,
      *
      * ------------------------------------------------------
      */
{
  int result = 0;

  if (sem == NULL)
    {
	result = EINVAL;
    }

#ifdef NEED_SEM

  else if (! ptw32_increase_semaphore (sem, 1))

#else /* NEED_SEM */

  else if (! ReleaseSemaphore (*sem, 1, 0))

#endif /* NEED_SEM */

    {
	result = EINVAL;
    }

  if (result != 0)
    {
      errno = result;
      return -1;
    }

  return 0;

}				/* sem_post */


int
sem_open (const char * name, int oflag, mode_t mode, unsigned int value)
{
  errno = ENOSYS;
  return -1;
}				/* sem_open */


int
sem_close (sem_t * sem)
{
  errno = ENOSYS;
  return -1;
}				/* sem_close */


int
sem_unlink (const char * name)
{
  errno = ENOSYS;
  return -1;
}				/* sem_unlink */


int
sem_getvalue (sem_t * sem, int * sval)
{
  errno = ENOSYS;
  return -1;
}				/* sem_getvalue */