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prioque.c

//
// implementation of "prioque.h" priority queue functions */
// (c) 198x/1998/2001 (minor updates) by Golden G. Richard III, Ph.D. */
//
// Major update October 2004.  See prioque.h for details.
//

#include <stdio.h>
#include <string.h>        
#include <stdlib.h>
#include "prioque.h"

// global lock on entire package
pthread_mutex_t global_lock=PTHREAD_MUTEX_INITIALIZER;  

// for init purposes
pthread_mutex_t initial_mutex=PTHREAD_MUTEX_INITIALIZER;   

// function prototypes for internal functions
void nolock_next_element(Queue *q);
void nolock_rewind_queue(Queue *q);
int nolock_element_in_queue(Queue *q, void *element);
void nolock_destroy_queue(Queue *q);
void local_nolock_next_element(Context *ctx);
void local_nolock_rewind_queue(Context *ctx);


void init_queue(Queue *q, int elementsize, int duplicates, 
            int (*compare)(void *e1, void *e2)) {

  q->queuelength = 0;
  q->elementsize = elementsize;
  q->queue = 0;
  q->duplicates = duplicates;
  q->compare = compare;
  nolock_rewind_queue(q);
  q->lock=initial_mutex;
}


void destroy_queue(Queue *q) {

  // lock entire queue
  pthread_mutex_lock(&(q->lock));
  
  nolock_destroy_queue(q);

  // release lock on queue
  pthread_mutex_unlock(&(q->lock));
}


void nolock_destroy_queue(Queue *q) {

  Queue_element temp;
  
  if (q != 0) {   
    while (q->queue != 0) {
      free(q->queue->info); 
      temp = q->queue;
      q->queue = q->queue->next;
      free(temp);
      (q->queuelength)--;
    }
  }

  nolock_rewind_queue(q);
}




int element_in_queue(Queue *q, void *element) {

  int found;
  // lock entire queue
  pthread_mutex_lock(&(q->lock));
  
  found = nolock_element_in_queue(q, element);
  
  // release lock on queue
  pthread_mutex_unlock(&(q->lock));
  
  return found;
}

int nolock_element_in_queue(Queue *q, void *element) {

  int found=0;

  if (q->queue != 0) {
    nolock_rewind_queue(q);
    while (! end_of_queue(q) && ! found) {
      if (q->compare(element, q->current->info) == 0) {
      found=1;
      }
      else {
      nolock_next_element(q);
      }
    }
  }
  if (! found) {
    nolock_rewind_queue(q);
  }
  
  return found;
}



void nolock_add_to_queue(Queue *q, void *element, int priority) {

   Queue_element new_element, ptr, prev=0;

   if (! q->queue ||   
       (q->queue && (q->duplicates || 
                 ! nolock_element_in_queue(q, element)))) {
     
     new_element = (Queue_element)malloc(sizeof(struct _Queue_element));
     if (new_element == 0) {
       fprintf(stderr,"Malloc failed in function add_to_queue()\n");
       exit(1);
     }
     new_element->info = (void *)malloc(q->elementsize);
     if (new_element->info == 0) {
       fprintf(stderr,"Malloc failed in function add_to_queue()\n");
       exit(1);
     }
     
     memcpy(new_element->info, element, q->elementsize);
     
     new_element->priority = priority;
     
     (q->queuelength)++;
     
     if (q->queue == 0) {
       new_element->next = 0;
       q->queue = new_element;
     }
     else if ((q->queue)->priority >= priority) {
       new_element->next = q->queue;
       q->queue = new_element;
     }
     else {
       ptr = q->queue;
       while (ptr != 0 && priority >= ptr->priority) {
       prev = ptr;
       ptr = ptr->next;
       }  
       
       new_element->next = prev->next;
       prev->next = new_element;
     }
     
     nolock_rewind_queue(q);
   }
}


void add_to_queue(Queue *q, void *element, int priority) {

   // lock entire queue
   pthread_mutex_lock(&(q->lock));

   nolock_add_to_queue(q, element, priority);

   // release lock on queue
   pthread_mutex_unlock(&(q->lock));
   
}


int empty_queue(Queue *q) {

    return q->queue == 0;
}   



void remove_from_front(Queue *q, void *element) {

    Queue_element temp;

    // lock entire queue
    pthread_mutex_lock(&(q->lock));
    
#if defined(CONSISTENCY_CHECKING)
   if (q->queue == 0) {
      fprintf(stderr,"NULL pointer in function remove_from_front()\n");
      exit(1);
   }
   else 
#endif 
   {

     memcpy(element, q->queue->info, q->elementsize);
     
     free(q->queue->info); 
     temp = q->queue;
     q->queue = q->queue->next;
     free(temp);
     (q->queuelength)--;
   }   
   
   nolock_rewind_queue(q);

   // release lock on queue
   pthread_mutex_unlock(&(q->lock));
}



void peek_at_current(Queue *q, void *element) {

  // lock entire queue
  pthread_mutex_lock(&(q->lock));
     
#if defined(CONSISTENCY_CHECKING)
   if (q->queue == 0 || q->current == 0) {
      fprintf(stderr,"NULL pointer in function peek_at_current()\n");
      exit(1);
   }
   else 
#endif 
   {
     
     memcpy(element, (q->current)->info, q->elementsize);
     
   // release lock on queue
     pthread_mutex_unlock(&(q->lock));
   }   
}


void *pointer_to_current(Queue *q) {

  void *data;

  // lock entire queue
  pthread_mutex_lock(&(q->lock));
    
#if defined(CONSISTENCY_CHECKING)
   if (q->queue == 0 || q->current == 0) {
      fprintf(stderr,"NULL pointer in function pointer_to_current()\n");
      exit(1);
   }
   else 
#endif 
   {

     data = (q->current)->info;

     // release lock on queue
     pthread_mutex_unlock(&(q->lock));
     
     return data;
   }   
}



int current_priority(Queue *q) {

  int priority;

  // lock entire queue
  pthread_mutex_lock(&(q->lock));
    
#if defined(CONSISTENCY_CHECKING)
   if (q->queue == 0 || q->current == 0) {
      fprintf(stderr,"NULL pointer in function peek_at_current()\n");
      exit(1);
   }
   else 
#endif 
   {

     priority = (q->current)->priority;

     // release lock on queue
     pthread_mutex_unlock(&(q->lock));

     return priority;
   }   
}



void update_current(Queue *q, void *element) {
    
  // lock entire queue
  pthread_mutex_lock(&(q->lock));

#if defined(CONSISTENCY_CHECKING)
   if (q->queue == 0 || q->current == 0) {
      fprintf(stderr,"NULL pointer in function update_current()\n");
      exit(1);
   }
   else 
#endif 
   {
      memcpy(q->current->info, element, q->elementsize);
   }   

   // release lock on queue
   pthread_mutex_unlock(&(q->lock));
}



void delete_current(Queue *q) {

  Queue_element temp;

  // lock entire queue
  pthread_mutex_lock(&(q->lock));
  
#if defined(CONSISTENCY_CHECKING)
  if (q->queue == 0 || q->current == 0) {
    fprintf(stderr,"NULL pointer in function delete_current()\n");
    exit(1);
  }
  else 
#endif 
    {

      free(q->current->info); 
      temp = q->current;
      
      if (q->previous == 0) {      /* deletion at beginning */
      q->queue = q->queue->next;
      q->current = q->queue; 
      }
      else {                    /* internal deletion */
      q->previous->next = q->current->next;
      q->current = q->previous->next;
      }

      free(temp);
      (q->queuelength)--;
      
    }
  
  // release lock on queue
  pthread_mutex_unlock(&(q->lock));
  
}    



int end_of_queue(Queue *q) {

  return (q->current == 0);

}


void next_element(Queue *q) {

  // lock entire queue
  pthread_mutex_lock(&(q->lock));
  
  nolock_next_element(q);
  
  // release lock on queue
  pthread_mutex_unlock(&(q->lock));
}


void nolock_next_element(Queue *q) {

#if defined(CONSISTENCY_CHECKING)
    if (q->queue == 0) {
      fprintf(stderr,"NULL pointer in function next_element()\n");
      exit(1);
    }
    else if (q->current == 0) {
      fprintf(stderr,"Advance past end in NULL pointer in function next_element()\n");
      exit(1);
    }
    else 
#endif 
   {
     q->previous = q->current;
     q->current = q->current->next;
   }
}



void rewind_queue(Queue *q) {
  
  // lock entire queue
  pthread_mutex_lock(&(q->lock));

  nolock_rewind_queue(q);
   // release lock on queue
  pthread_mutex_unlock(&(q->lock));
}

void nolock_rewind_queue(Queue *q) {

  q->current = q->queue;
  q->previous = 0;
  
}


int queue_length(Queue *q) {

    return q->queuelength;
}


void copy_queue(Queue *q1, Queue *q2) {

    Queue_element temp, new_element, endq1;

    // to avoid deadlock, this function acquires a global package
    // lock!
    pthread_mutex_lock(&global_lock);

    // lock entire queues q1, q2
    pthread_mutex_lock(&(q1->lock));
    pthread_mutex_lock(&(q2->lock));
    
    /* free elements in q1 before copy */
    
    nolock_destroy_queue(q1);

    /* now make q1 a clone of q2 */

    q1->queuelength = 0;
    q1->elementsize = q2->elementsize;
    q1->queue = 0;
    q1->duplicates = q2->duplicates;
    q1->compare = q2->compare;

    temp = q2->queue;
    endq1 = q1->queue;

    while (temp != 0) {
      new_element = (Queue_element)malloc(sizeof(struct _Queue_element));

      if (new_element == 0) {
          fprintf(stderr,"Malloc failed in function copy_queue()\n");
          exit(1);
      }

      new_element->info = (void *)malloc(q1->elementsize);
      if (new_element->info == 0) {
          fprintf(stderr,"Malloc failed in function copy_queue()\n");
          exit(1);
      }
      memcpy(new_element->info, temp->info, q1->elementsize);
   
      new_element->priority = temp->priority;
      new_element->next = 0;

      (q1->queuelength)++;
   
      if (endq1 == 0) {
          q1->queue = new_element;
      }
      else {
          endq1->next = new_element;
      }
      endq1 = new_element;
      temp = temp->next;
    }

    nolock_rewind_queue(q1);

    // release locks on q1, q2
    pthread_mutex_unlock(&(q2->lock));
    pthread_mutex_unlock(&(q1->lock));

    // release global package lock
    pthread_mutex_unlock(&global_lock);

}



int equal_queues(Queue *q1, Queue *q2) {

    Queue_element temp1, temp2;
    int same = TRUE;

    // to avoid deadlock, this function acquires a global package
    // lock!
    pthread_mutex_lock(&global_lock);

    // lock entire queues q1, q2
    pthread_mutex_lock(&(q1->lock));
    pthread_mutex_lock(&(q2->lock));

    if (q1->queuelength != q2->queuelength || q1->elementsize != q2->elementsize) {
      same = FALSE;
    }
    else {
      temp1 = q1->queue;
      temp2 = q2->queue;
      while (same && temp1 != 0) {
          same = (! memcmp(temp1->info, temp2->info, q1->elementsize) &&
                temp1->priority == temp2->priority);
          temp1=temp1->next;
          temp2=temp2->next;
      }
    }

    // release locks on q1, q2
    pthread_mutex_unlock(&(q2->lock));
    pthread_mutex_unlock(&(q1->lock));

    // release global package lock
    pthread_mutex_unlock(&global_lock);

    return same;
}


void merge_queues(Queue *q1, Queue *q2) {

    Queue_element temp;

    // to avoid deadlock, this function acquires a global package
    // lock!
    pthread_mutex_lock(&global_lock);

    // lock entire queues q1, q2
    pthread_mutex_lock(&(q1->lock));
    pthread_mutex_lock(&(q2->lock));

    temp = q2->queue;

    while (temp != 0) {
      nolock_add_to_queue(q1, temp->info, temp->priority);
      temp=temp->next;
    }

    nolock_rewind_queue(q1);

    // release locks on q1, q2
    pthread_mutex_unlock(&(q2->lock));
    pthread_mutex_unlock(&(q1->lock));

    // release global package lock
    pthread_mutex_unlock(&global_lock);

}



void local_peek_at_current(Context *ctx, void *element) {

  // lock entire queue
  pthread_mutex_lock(&(ctx->queue->lock));

#if defined(CONSISTENCY_CHECKING)
   if (ctx->queue == 0 || ctx->current == 0) {
      fprintf(stderr,"NULL pointer in function peek_at_current()\n");
      exit(1);
   }
   else 
#endif 
   {
     
     memcpy(element, (ctx->current)->info, ctx->queue->elementsize);
     
     // release lock on queue
     pthread_mutex_unlock(&(ctx->queue->lock));

   }   
}


void *local_pointer_to_current(Context *ctx) {

  void *data;

  // lock entire queue
  pthread_mutex_lock(&(ctx->queue->lock));
    
#if defined(CONSISTENCY_CHECKING)
   if (ctx->queue == 0 || ctx->current == 0) {
      fprintf(stderr,"NULL pointer in function pointer_to_current()\n");
      exit(1);
   }
   else 
#endif 
   {

     data = (ctx->current)->info;

     // release lock on queue
     pthread_mutex_unlock(&(ctx->queue->lock));
     
     return data;
   }   
}


int local_current_priority(Context *ctx) {

  int priority;

  // lock entire queue
  pthread_mutex_lock(&(ctx->queue->lock));
    
#if defined(CONSISTENCY_CHECKING)
   if (ctx->queue == 0 || ctx->current == 0) {
      fprintf(stderr,"NULL pointer in function peek_at_current()\n");
      exit(1);
   }
   else 
#endif 
   {
     priority = (ctx->current)->priority;

     // release lock on queue
     pthread_mutex_unlock(&(ctx->queue->lock));

     return priority;
   }   
}



void local_update_current(Context *ctx, void *element) {
    
  // lock entire queue
  pthread_mutex_lock(&(ctx->queue->lock));

#if defined(CONSISTENCY_CHECKING)
   if (ctx->queue == 0 || ctx->current == 0) {
      fprintf(stderr,"NULL pointer in function update_current()\n");
      exit(1);
   }
   else 
#endif 
   {
      memcpy(ctx->current->info, element, ctx->queue->elementsize);
   }   

   // release lock on queue
   pthread_mutex_unlock(&(ctx->queue->lock));
}



void local_delete_current(Context *ctx) {

  Queue_element temp;

  // lock entire queue
  pthread_mutex_lock(&(ctx->queue->lock));
  
#if defined(CONSISTENCY_CHECKING)
  if (ctx->queue == 0 || ctx->current == 0) {
    fprintf(stderr,"NULL pointer in function delete_current()\n");
    exit(1);
  }
  else 
#endif 
    {

      free(ctx->current->info); 
      temp = ctx->current;
      
      if (ctx->previous == 0) {      /* deletion at beginning */
      ctx->queue->queue = ctx->queue->queue->next;
      ctx->current = ctx->queue->queue; 
      }
      else {                         /* internal deletion */
      ctx->previous->next = ctx->current->next;
      ctx->current = ctx->current->next;
      }

      free(temp);
      (ctx->queue->queuelength)--;
      
    }
  
  // release lock on queue
  pthread_mutex_unlock(&(ctx->queue->lock));
  
}    



int local_end_of_queue(Context *ctx) {

  return (ctx->current == 0);

}


void local_next_element(Context *ctx) {

  // lock entire queue
  pthread_mutex_lock(&(ctx->queue->lock));
  
  local_nolock_next_element(ctx);
  
  // release lock on queue
  pthread_mutex_unlock(&(ctx->queue->lock));
}


void local_nolock_next_element(Context *ctx) {

#if defined(CONSISTENCY_CHECKING)
    if (ctx->queue == 0) {
      fprintf(stderr,"NULL pointer in function next_element()\n");
      exit(1);
    }
    else if (ctx->current == 0) {
      fprintf(stderr,"Advance past end in NULL pointer in function next_element()\n");
      exit(1);
    }
    else 
#endif 
   {
     ctx->previous = ctx->current;
     ctx->current = ctx->current->next;
   }
}



void local_rewind_queue(Context *ctx) {
  
  // lock entire queue
  pthread_mutex_lock(&(ctx->queue->lock));

  local_nolock_rewind_queue(ctx);

   // release lock on queue
  pthread_mutex_unlock(&(ctx->queue->lock));
}

void local_nolock_rewind_queue(Context *ctx) {

  ctx->current = ctx->queue->queue;
  ctx->previous = 0;
  
}

void local_init_context(Queue *q, Context *ctx) {
  ctx->queue = q;
  ctx->current = q->queue;
  ctx->previous=0;
}


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