（第四章 2）生产者-消费者模型

输出大致像这样：

[hadoop@sam1 test]$ ./producer_consumer [P0] Producing 0 ...[P1] Producing 0 ...[P1] Producing 1 ...[P0] Producing 1 ...------> [C1] Comsuming 0 ...------> [C1] Comsuming 0 ...[P2] Producing 0 ...[P2] Producing 1 ...------> [C2] Comsuming 1 ...------> [C0] Comsuming 1 ...------> [C0] Comsuming 0 ...------> [C1] Comsuming 1 ...[P1] Producing 2 ...[P1] Producing 3 ...------> [C0] Comsuming 2 ...------> [C0] Comsuming 3 ...[P0] Producing 2 ...[P2] Producing 2 ...------> [C2] Comsuming 2 ...[P2] Producing 3 ...[P0] Producing 3 ...------> [C1] Comsuming 2 ...------> [C2] Comsuming 3 ...------> [C2] Comsuming 3 ...

?

代码：

#include <pthread.h>#include <stdio.h>#include <stdlib.h>#include </usr/include/semaphore.h>#define BUFF_SIZE   5/* total number of slots */#define NP          3/* total number of producers */#define NC          3/* total number of consumers */#define NITERS      4/* number of items produced/consumed */typedef struct {    int buf[BUFF_SIZE];   /* shared var */    int in;           /* buf[in%BUFF_SIZE] is the first empty slot */    int out;          /* buf[out%BUFF_SIZE] is the first full slot */    sem_t full;       /* keep track of the number of full spots */    sem_t empty;      /* keep track of the number of empty spots */    sem_t mutex;      /* enforce mutual exclusion to shared data */} sbuf_t;sbuf_t shared;void *Producer(void *arg){    int i, item, index;    //index是线程编号    index = (int)arg;    for (i=0; i < NITERS; i++) {        /* Produce item */        item = i;        /* Prepare to write item to buf ??*/        /* If there are no empty slots, wait */        sem_wait(&shared.empty);         /* If another thread uses the buffer, wait */        sem_wait(&shared.mutex);        shared.buf[shared.in] = item;        shared.in = (shared.in+1)%BUFF_SIZE;        printf("[P%d] Producing %d ...\n", index, item);fflush(stdout);        /* Release the buffer */        sem_post(&shared.mutex);        /* Increment the number of full slots */        sem_post(&shared.full);        /* Interleave  producer and consumer execution */        if (i % 2 == 1) sleep(1);    }    return NULL;}void *Consumer(void *arg){    /* Fill in the code here */int i,item,index;index=(int)arg;for(i=0;i<NITERS;i++){item=i;sem_wait(&shared.full);sem_wait(&shared.mutex);printf("------> [C%d] Comsuming %d ...\n",index,shared.buf[shared.out]);//fflush(stdout);shared.out=(shared.out+1)%BUFF_SIZE;sem_post(&shared.mutex);sem_post(&shared.empty);}return NULL;}int main(){    pthread_t idP, idC;    int index;    //注意：    //1. 信号量一定要初始化，否则程序卡住，而且不报错    //2. value=1的信号量等同于互斥锁??    sem_init(&shared.mutex,0,1);    sem_init(&shared.full, 0, 0);    sem_init(&shared.empty, 0, BUFF_SIZE);    /* Insert code here to initialize mutex*/    for (index = 0; index < NP; index++)    {         /* Create a new producer */       pthread_create(&idP, NULL, Producer, (void*)index);    }    /* Insert code here to create NC consumers */for(index=0;index<NC;index++){pthread_create(&idC,NULL,Consumer,(void*)index);}    pthread_exit(NULL);//仅仅结束主线程，进程不结束（对其他子线程不影响）}