/****************************************************************************\
*                                       
*                                Written by
*                     Tom Wagner (wagner@cs.umass.edu)
*                  at the Distributed Problem Solving Lab
*       Department of Computer Science, University of Massachusetts,
*                            Amherst, MA 01003
*                                     
*        Copyright (c) 1995 UMASS CS Dept. All rights are reserved.
*                                     
*           Development of this code was partially supported by:
*                        ONR grant N00014-92-J-1450
*                         NSF contract CDA-8922572
*                                      
* ---------------------------------------------------------------------------
* 
* This code is free software; you can redistribute it and/or modify it.
* However, this header must remain intact and unchanged.  Additional
* information may be appended after this header.  Publications based on
* this code must also include an appropriate reference.
* 
* This code 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.
* 
\****************************************************************************/

#include "./H/semaphore.h"

  // needed for each function to be able to write to logFile
//#include "./../../LogFile/H/logFile.h"
/*extern LogFile *logFile;*/

/*
 * function must be called prior to semaphore use.
 *
 */
void
semaphore_init(Semaphore * s, int initValue)
{
    if (initValue >= 0)
      s->v = initValue;
 //   else {
     // logFile->WriteString(llError, __FILE__ 
//			   "%d:Error in initValue for semaphore", __LINE__);
  //  }

    if (pthread_mutex_init(&(s->mutex), pthread_mutexattr_default) == -1)
      ;
 //     logFile->WriteString(llError, __FILE__ 
//			   "%d:Error setting up semaphore mutex", __LINE__);

    if (pthread_cond_init(&(s->cond), pthread_condattr_default) == -1)
    ;
    //  logFile->WriteString(llError, __FILE__ 
//			   "%d:Error setting up semaphore condition signal", 
//			   __LINE__);
}

/*
 * function should be called when there is no longer a need for
 * the semaphore.
 *
 */
void
semaphore_destroy(Semaphore * s)
{
    if (pthread_mutex_destroy(&(s->mutex)) == -1)
      ;
      //logFile->WriteString(llError, __FILE__ 
//			   "%d:Error destroying semaphore mutex", __LINE__);

    if (pthread_cond_destroy(&(s->cond)) == -1)
      ;
      //logFile->WriteString(llError, __FILE__ 
//			   "%d:Error destroying semaphore condition signal", 
//			   __LINE__);
}

/*
 * function increments the semaphore and signals any threads that
 * are blocked waiting a change in the semaphore.
 *
 */
int
semaphore_up(Semaphore * s)
{
    int         value_after_op;

    tw_pthread_mutex_lock(&(s->mutex));

    (s->v)++;
    value_after_op = s->v;

    tw_pthread_mutex_unlock(&(s->mutex));
    tw_pthread_cond_signal(&(s->cond));

    return(value_after_op);
}

/*
 * function decrements the semaphore and blocks if the semaphore is
 * <= 0 until another thread signals a change.
 *
 */
int
semaphore_down(Semaphore * s)
{
    int         value_after_op;

    tw_pthread_mutex_lock(&(s->mutex));

    if (s->v <= 0 )
     ;
     // logFile->WriteString(llDebug, __FILE__ "%d:Nekdo pujde spat", __LINE__);

    while(s->v <= 0)
    {
     tw_pthread_cond_wait(&(s->cond), &(s->mutex));
    }

    (s->v)--;
    value_after_op = s->v;

    tw_pthread_mutex_unlock(&(s->mutex));

    return(value_after_op);
}

/*
 * function does NOT block but simply decrements the semaphore.
 * should not be used instead of down -- only for programs where
 * multiple threads must up on a semaphore before another thread
 * can go down, i.e., allows programmer to set the semaphore to
 * a negative value prior to using it for synchronization.
 *
 */
int
semaphore_decrement(Semaphore * s)
{
    int         value_after_op;

    tw_pthread_mutex_lock(&(s->mutex));
    s->v--;
    value_after_op = s->v;
    tw_pthread_mutex_unlock(&(s->mutex));

    return(value_after_op);
}

/*
 * function returns the value of the semaphore at the time the
 * critical section is accessed.  obviously the value is not guarenteed
 * after the function unlocks the critical section.  provided only
 * for casual debugging, a better approach is for the programmar to
 * protect one semaphore with another and then check its value.
 * an alternative is to simply record the value returned by semaphore_up
 * or semaphore_down.
 *
 */
int
semaphore_value(Semaphore * s)
{
    /* not for sync */
    int         value_after_op;

    tw_pthread_mutex_lock(&(s->mutex));
    value_after_op = s->v;
    tw_pthread_mutex_unlock(&(s->mutex));

    return(value_after_op);
}



/* -------------------------------------------------------------------- */
/* The following functions replace standard library functions in that   */
/* they exit on any error returned from the system calls.  Saves us     */
/* from having to check each and every call above.                      */
/* -------------------------------------------------------------------- */


int
tw_pthread_mutex_unlock(pthread_mutex_t * m)
{
    int         return_value;

    if ((return_value = pthread_mutex_unlock(m)) == -1)
      ;
      //logFile->WriteString(llError, __FILE__ 
//			   "%d:pthread_mutex_unlock", __LINE__);

    return(return_value);
}

int
tw_pthread_mutex_lock(pthread_mutex_t * m)
{
    int         return_value;

    if ((return_value = pthread_mutex_lock(m)) == -1)
      ;
 //     logFile->WriteString(llError, __FILE__ 
//			   "%d:pthread_mutex_lock", __LINE__);

    return(return_value);
}

int
tw_pthread_cond_wait(pthread_cond_t * c, pthread_mutex_t * m)
{
    int         return_value;

    if ((return_value = pthread_cond_wait(c, m)) == -1)
      ;
      //logFile->WriteString(llError, __FILE__ "%d:pthread_cond_wait", __LINE__);

    return(return_value);
}

int
tw_pthread_cond_signal(pthread_cond_t * c)
{
    int         return_value;

    if ((return_value = pthread_cond_signal(c)) == -1)
      ;
      //logFile->WriteString(llError, __FILE__ 
//			   "%d:pthread_cond_signal", __LINE__);

    return(return_value);
}