/************************************************************
  File:          gsemaphore.cc
  Description:   A program that simulates a dependancy graph 
                 for a set of threads.
                 The functions for manipulating a general
                 semaphore.
                                                         
  Author:        Dana Vrajitoru                          
  Organization:  IUSB                                    
  Date:          November 24, 2004
**************************************************************/

#include "gsemaphore.h"

// Assigns the value of the second parameter to the internal semaphore
// value and initializes the mutex.
void Init_sem(Gsemaphore &sem, int val)
{
  sem.value = val;
  pthread_mutex_init(&(sem.mutex), NULL);
}

// Waits until the value has become 0, then increments it. It's a
// blocking function.
void Test_and_inc(Gsemaphore &sem)
{
  // To be implemented by the student.
}

// Decreases the value of the semaphore without testing it. It still
// must protect the value as a critical section.
void Dec(Gsemaphore &sem)
{
  pthread_mutex_lock(&(sem.mutex));
  sem.value--;
  pthread_mutex_unlock(&(sem.mutex));
}