#include <sys/types.h>#include <sys/ipc.h>
#include <sys/sem.h>#include <stdio.h>
#define KEY (key_t)	//后面自己使用兩個隨機的數值
#define KEY2 (key_t)
#define MAX_BUFFER_SIZE	10		//緩沖區最大緩沖個數
union semun {
	int val;
	struct semid_ds *buf;
	ushort *array;
};						//用于semctl函數的控制結構

typedef struct _tagShareBuffer{
	int buffer[MAX_BUFFER_SIZE];
	int writer;
	int reader;
}SHAREBUFFER;			//共享內存中的結構

int main(){	int	  shmid;		//共享內存id	char* shmPtr;		//指向共享內存首地址的指針
	
	SHAREBUFFER* pSharebuffer;	//共享內存結構體指針
	int product = 0;			//產品值，生產一件自加1
	
	int	semid;	//信號集id
	struct sembuf mutex,empty,full;  //三個信號量的控制變量
	
	int i;
	
	//
	//創建或打開一個鍵值為KEY的信號量集合，包含3個信號量，并返回一個信號量集合id
	//	
	if ((semid = semget(KEY,3,IPC_CREAT|0660)) == -1)
	{
		printf("semget error! \n");
		
		return -1;
	}

	/*********************************************************
	*	初始化信號量的初值
	*	第0個信號量用于互斥，初值為1
	*	第1個信號量用于生產者，初值為MAX_BUFFER_SIZE
	*	第2個信號量用于消費者，初值為0
	*	arg是用于給信號量賦值的一個中間過渡變量，不必理會
	*********************************************************/
	union semun arg[3];
	arg[0].val = 1;
	arg[1].val = MAX_BUFFER_SIZE;
	arg[2].val = 0;

	for(i=0;i<3;i++)
		semctl(semid,i,SETVAL,arg[i]);	//賦值語句，因為信號是核心對象，所以要使用特殊的系統調用賦值
	
	for(i=0;i<3;i++)
		printf("The semval(%d) = %d\n",i,semctl(semid,i,GETVAL,NULL));

	//**************************
	//創建或打開一個鍵值為KEY的共享內存塊，并返回它的id
	//將KEY值加1，避免與信號量集的key相同
	if ((shmid = shmget(KEY+1,sizeof(SHAREBUFFER),IPC_CREAT)) < 0)	{		printf("shmget error!\n");		return -1;	}
	
	//
	//將共享內存映射到進程空間里，并返回共享內存首地址
	//	if((shmPtr = (char*)shmat(shmid,0,0)) == (void*)-1)	{		printf("shmat error!\n");		return -1;	}
	
	memset((void*)shmPtr,0,sizeof(SHAREBUFFER));	//將共享內存空間清0
	
	pSharebuffer = (SHAREBUFFER*)shmPtr;

	//
	//下面開始向ShareBuffer中生產產品
	//
	while(1)
	{
		empty.sem_num = 1;		//指操作哪個信號量
		empty.sem_op  = -1;		//要對信號量的值作減1操作
		empty.sem_flg = 0;		//控制標識符
		semop(semid,&empty,1);	//P(empty)
		
		pSharebuffer->buffer[pSharebuffer->writer] = product;
		
		for(i=0;i<3;i++)
			printf("The semval(%d) = %d\n",i,semctl(semid,i,GETVAL,NULL));
		
		printf("Produced the product into buffer[%d] = %d;\n",pSharebuffer->writer,product);
		
		product++;
		
		mutex.sem_num = 0;
		mutex.sem_op  = -1;
		mutex.sem_flg = 0;
		semop(semid,&mutex,1);	//P(mutex)
		
		pSharebuffer->writer = (pSharebuffer->writer + 1) % MAX_BUFFER_SIZE;
		
		mutex.sem_num = 0;
		mutex.sem_op  = 1;
		mutex.sem_flg = 0;
		semop(semid,&mutex,1);	//V(mutex)
		
		full.sem_num = 2;
		full.sem_op	= 1;
		full.sem_flg = 0;
		semop(semid,&full,1); //V(full)

		sleep(1); //調節一下生產速度^_^
	}

	return 0;}