线程的互斥锁和条件变量通信机制

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>

#define BUFFER_SIZE 2
struct prodcons
{
int buffer[BUFFER_SIZE];
pthread_mutex_t lock;
int readpos,writepos;
pthread_cond_t notempty;
pthread_cond_t notfull;
};

void init(struct prodcons *prod)
{
pthread_mutex_init(&prod->lock,NULL);
pthread_cond_init(&prod->notempty,NULL);
pthread_cond_init(&prod->notfull,NULL);
prod->readpos=0;
prod->writepos=0;
}

void put(struct prodcons *prod, int data)
{
pthread_mutex_lock(&prod->lock);
while((prod->writepos+1)%BUFFER_SIZE==prod->readpos)
{
printf("producer wait for not full\n");
pthread_cond_wait(&prod->notfull,&prod->lock);
}
prod->buffer[prod->writepos]=data;
prod->writepos++;
if(prod->writepos>=BUFFER_SIZE)
prod->writepos=0;
pthread_cond_signal(&prod->notempty);
pthread_mutex_unlock(&prod->lock);
}

int get(struct prodcons *prod)
{
int data;
pthread_mutex_lock(&prod->lock);
while(prod->writepos==prod->readpos)
{
printf("consumer wait for not empty\n");
pthread_cond_wait(&prod->notempty,&prod->lock);
}
data=prod->buffer[prod->readpos];
prod->readpos++;
if(prod->readpos>=BUFFER_SIZE)
prod->readpos=0;
pthread_cond_signal(&prod->notfull);
pthread_mutex_unlock(&prod->lock);
return data;
}

#define OVER (-1)

struct prodcons buffer;

void *producer(void * data)
{
int n;
for(n=1;n<=5;n++)
{
printf("producer sleep 1 second...\n");
sleep(1);
printf("put the %d product\n",n);
put(&buffer,n);
}
for(n=6;n<=10;n++)
{
printf("producer sleep 3 second...\n");
sleep(3);
printf("put the %d product\n",n);
put(&buffer,n);
}
put(&buffer,OVER);
printf("producer stopped\n");
return NULL;
}

void *consumer(void *data)
{
int d=0;
while(1)
{
printf("consumer sleep 2 second...\n");
sleep(2);
d=get(&buffer);
printf("get the %d product\n",d);
if(d==OVER)
break;
}
printf("consumer stopped\n");
return NULL;
}

int main(int argc, char *argv[])
{
pthread_t th_a,th_b;
void *retval;
init(&buffer);
pthread_create(&th_a,NULL,producer,0);
pthread_create(&th_b,NULL,consumer,0);
pthread_join(th_a,&retval);
pthread_join(th_b,&retval);
return 0;
}