#include "csapp.c"


sem_t step1_done, step2_done;

void*  foo1() {
    printf("test1 is done\n");
    V(&step1_done);                  //step1執(zhí)行完畢了，那么foo2的阻塞就會被解開
    P(&step2_done);                  //測試是否step2執(zhí)行完畢，
    printf("test3 is done\n");
    return NULL;
}

void* foo2() {
    P(&step1_done);
    printf("test2 is done\n");
    V(&step2_done);                  //step2執(zhí)行完畢，解開打印step的鎖
    return NULL;
}

int main()
{
    pthread_t tid1, tid2;
    Sem_init(&step1_done, 0, 0);            //第二個參數(shù)為0：在線程之間進(jìn)行， 第三個參數(shù)初始化都為零
    Sem_init(&step2_done, 0, 0);


    Pthread_create(&tid1, NULL, foo1, NULL);
    Pthread_create(&tid2, NULL, foo2, NULL);


    //保證線程執(zhí)行完畢之后主線程才退出，否則線程都執(zhí)行不了了
    Pthread_join(tid1, NULL);
    Pthread_join(tid2, NULL);


    exit(0);

}

void sbuf_insert(subf_t* sp, int item) {
    sem_wait(&sp->mutex);
  	sem_wait(&sp->slots);

    //將項(xiàng)目放進(jìn)buf中
    sp->buf[(++sp->rear) % (sp->n)] = item;

    sem_post(&sp->items);
    sem_post(&sp->mutex);

}


void sbuf_remove(sbuf_t* sp) {
  sem_wait(&sp->mutex);
  sem_wait(&sp->items);
  
  
  //do works
  
  sem_post(&sp->slots);
  sem_post(&sp->mutex);
}

#include <stdio.h>
#include <stdlib.h>
#include <semaphore.h>

typedef struct sbuf{
    int *buf;               /*堆上開辟的內(nèi)存，用于存儲*/
    int n;                  /*cap of the buf*/
    int front;              //第一個item
    int rear;               //最后一個item

    sem_t mutex;            //獲取臨界區(qū)的鎖
    sem_t slots;            //空槽數(shù)目
    sem_t items;            //已經(jīng)生產(chǎn)了的數(shù)目
}subf_t;

void sbuf_init(subf_t* sp, int n) {
    sp->n     = n;
    sp->buf   = static_cast<int *>(calloc(n, sizeof(int)));
    sp->front = 0;
    sp->rear  = 0;

    sem_init(&sp->mutex, 0, 1);
    sem_init(&sp->slots, 0, n);
    sem_init(&sp->items, 0, 0);
}

void sbuf_deinit(subf_t*sp) {
    free(sp->buf);
}


void sbuf_insert(subf_t* sp, int item) {
    //首先應(yīng)該對信號量slots判斷，你生產(chǎn)者看中
    sem_wait(&sp->slots);
    sem_wait(&sp->mutex);

    //將項(xiàng)目放進(jìn)buf中
    sp->buf[(++sp->rear) % (sp->n)] = item;


    //CSAPP中提到，解鎖的順序一般是和加鎖的順序是相反的
    sem_post(&sp->mutex);
    sem_post(&sp->items);
}

int  sbuf_remove(subf_t* sp) {
    int item;
    sem_wait(&sp->items);       //我看上哪個格子的產(chǎn)品了
    sem_wait(&sp->mutex);

    item = sp->buf[(++sp->front) % (sp->n)];

    sem_post(&sp->mutex);
    sem_post(&sp->slots);
    return item;
}

int readcnt = 0;
sem_t ,mutex = 1, w = 1;

void reader() {
  while (1) {
    P(&mutex);
    readcnt++;
    if (readcnt == 1) 	//第一個進(jìn)入的讀者
      P(&w);						//上鎖，寫者不能寫了
    V(&mutex);					//解開對于readcnt的保護(hù)鎖
    
    /*
    		臨界區(qū)的工作
    
    */
    
    P(&mutex);
    readcnt--;
    if (readcnt == 0) 
      V(&w);								//最后一個讀者了， 解開阻塞寫者的鎖
    V(&mutex);							//解開對readcnt的保護(hù)鎖
  }
}

void writer() {
  while (1) {
    P(&w);
    
    /*
    	臨界區(qū)工作
    
    */
    V(&w);
  }
}