操作系统课程设计读者写者问题源程序.txt

用c实现读者写者问题

/*
Reader-Writer problem
Class:0504
NO.:0120510340412
Name:Song Yuanlin
Year.Month:2008.6
*/

#include<stdio.h>
#include<pthread.h>
#include<semaphore.h>
#include<stdlib.h>
void *reader(void *args);
void *writer(void *args);
pthread_mutex_t  mutex;
sem_t wrt;
int count=0;
int share[20];
time_t end;     //define the thread running time
int position1=0;  //define the writer's position
int position2=0;  //define the reader's position

/*main function*/
int main(int argc,char **argv)
{       end=time(NULL)+5;
        pthread_mutex_init(&mutex,NULL);
        sem_init(&wrt,0,1);
        pthread_t r1,r2,r3,r4,w1,w2,w3;
        int res;
/*create the thread for every reader and writer*/
        res=pthread_create(&w1,NULL,(void*)writer,"Writer1");
        res=pthread_create(&r1,NULL,(void*)reader,"Reader1");
        res=pthread_create(&w2,NULL,(void*)writer,"Writer2");
        res=pthread_create(&r2,NULL,(void*)reader,"Reader2");
        res=pthread_create(&r3,NULL,(void*)reader,"Reader3");
        res=pthread_create(&w3,NULL,(void*)writer,"writer3");
        res=pthread_create(&r4,NULL,(void*)reader,"Reader4");

        res=pthread_join(w1,NULL);
        res=pthread_join(r1,NULL);
        res=pthread_join(w2,NULL);
        res=pthread_join(r2,NULL);
        res=pthread_join(r3,NULL);
        res=pthread_join(w3,NULL);
        res=pthread_join(r4,NULL);
        
	return 0;
   }

/*reader thread function*/
void *reader(void *args)
{	int i;
	while(time(NULL)<end)
      {  pthread_mutex_lock(&mutex);
         count++;
         if(count==1)
           sem_wait(&wrt);
         pthread_mutex_unlock(&mutex);
	 if(position2<position1)
	    position2++;
	 else
	    position2=1;
         printf(" %s is reading %d                The current position is %d\n",(char*)args,position2,position2);
 //display the reader's number and the current pointer        
	 printf("------------------------The current content of the sharearea----------------------\n");
	 for(i=0;i<20;i++)
	{
	  printf("| %d |",share[i]);
	}
	 printf("\n=================================================================================\n\n");
	 pthread_mutex_lock(&mutex);
         count--;
         if(count==0)
           sem_post(&wrt);
        pthread_mutex_unlock(&mutex);
	sleep(1);
      }
 }

/*writer thread function*/
void *writer(void *args)
 {	int i;
	while(time(NULL)<end)
      {
        sem_wait(&wrt);
	if(position1<20)
       {
	 share[position1]=position1+1;
	 position1++;
	 printf("%s is writing %d             The current position is %d\n",(char*)args,position1,position1);
//display the writer's number and the current pointer
	 printf("----------------The current content of the sharearea-----------------\n");
	 for(i=0;i<20;i++)
	 {
	   printf("| %d |",share[i]);     //display the current of the sharearea
	 }
	 printf("\n====================================================================\n\n");
	 sem_post(&wrt);
	 sleep(3);
        }
       }
 }