操作系统上机作业-- 使用信号量解决生产者、计算者、消费者问题（多线程）

pc2.c: 使用信号量解决生产者、计算者、消费者问题

•   功能和前面的实验相同，使用信号量解决

实现思路:
生产者、计算者、消费者三者之间的关系和上一个编程任务一样，不一样的是，将互斥量、条件变量封装起来作为信号量，处理方式基本和上一个编程任务一样
实现代码：

#include<stdio.h>
#include<pthread.h>
#include<unistd.h>#define CAPACITY 4char buffer1[4];
char buffer2[4];int crea; //生产者 
int comp1;//计算者 
int comp2;//计算者 
int cons; //消费者 int buffer1_is_empty(){return crea==comp1;
}int buffer1_is_full(){return (crea+1)%CAPACITY==comp1;
}int buffer2_is_empty(){return comp2==cons;
}int buffer2_is_full(){return (cons+1)%CAPACITY==comp2;
}int get_item1(){int item;item=buffer1[comp1];comp1=(comp1+1)%CAPACITY;return item;
}int get_item2(){int item;item=buffer2[cons];cons=(cons+1)%CAPACITY;return item;
}int put_item1(int item){buffer1[crea]=item;crea=(crea+1)%CAPACITY;
}int put_item2(int item){buffer2[comp2]=item;comp2=(comp2+1)%CAPACITY;
}typedef struct{int value;pthread_mutex_t mutex;pthread_cond_t  cond;
}sema_t;void sema_init(sema_t *sema,int value){sema->value=value;pthread_mutex_init(&sema->mutex,NULL);pthread_cond_init(&sema->cond,NULL);
}void sema_wait(sema_t *sema){pthread_mutex_lock(&sema->mutex);sema->value--;while(sema->value<0)pthread_cond_wait(&sema->cond,&sema->mutex);pthread_mutex_unlock(&sema->mutex);
}void sema_signal(sema_t *sema){pthread_mutex_lock(&sema->mutex);++sema->value;pthread_cond_signal(&sema->cond);pthread_mutex_unlock(&sema->mutex);
}sema_t mutex_sema1;
sema_t empty_buffer1_sema;
sema_t full_buffer1_sema;sema_t mutex_sema2;
sema_t empty_buffer2_sema;
sema_t full_buffer2_sema;#define ITEM_COUNT  (CAPACITY *2)void *consumer(void *arg){int i;int item;for(i=0;i<ITEM_COUNT;i++){sema_wait(&full_buffer2_sema);sema_wait(&mutex_sema2);item=get_item2();sema_signal(&mutex_sema2);sema_signal(&empty_buffer2_sema);printf("                   consume item:%c\n",item);}return NULL;
}void *computer(void *arg){int i;int item;for(i=0;i<ITEM_COUNT;i++){sema_wait(&full_buffer1_sema);sema_wait(&mutex_sema1);item=get_item1();sema_signal(&mutex_sema1);sema_signal(&empty_buffer1_sema);printf("        computer get item:%c\n",item);sema_wait(&empty_buffer2_sema);sema_wait(&mutex_sema2);item-=32;put_item2(item);printf("        computer put item:%c\n",item);sema_signal(&mutex_sema2);sema_signal(&full_buffer2_sema);}return NULL;
}void create(){int i;int item;for(i=0;i<ITEM_COUNT;i++){sema_wait(&empty_buffer1_sema);sema_wait(&mutex_sema1);item=i+'a';put_item1(item);printf("create item:%c\n",item);sema_signal(&mutex_sema1);sema_signal(&full_buffer1_sema);}
}int main(){pthread_t computer_tid;pthread_t consumer_tid;sema_init(&mutex_sema1,1);sema_init(&empty_buffer1_sema,CAPACITY-1);sema_init(&full_buffer1_sema,0);sema_init(&mutex_sema2,1);sema_init(&empty_buffer2_sema,CAPACITY-1);sema_init(&full_buffer2_sema,0);pthread_create(&consumer_tid,NULL,consumer,NULL);pthread_create(&computer_tid,NULL,computer,NULL);create();pthread_join(consumer_tid,NULL);pthread_join(computer_tid,NULL);return 0;
}