linux网络编程-进程间通信——信号量2

#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/sem.h>
#include <stdio.h>
#include <stdlib.h>
#include<errno.h>

int gSemid = 0;
typedef int sem_t;
#define ERR_EXIT(m) \
        do \
        { \
            perror(m); \
            exit(EXIT_FAILURE); \
        }while(0)

sem_t CreateSem(key_t key, int initValue, int semNum)
{
    union semun sem;
    sem_t semid;
    sem.val = initValue;

    semid = semget(key, 5, IPC_CREAT | IPC_EXCL | 0666);//创建信号量个数为1
    if(-1 == semid)
    {
        ERR_EXIT("semget");
    }
    for(int i=0;i<semNum;i++)
    {
        semctl(semid, i, SETVAL, sem);//参数2-要操作的信号量在信号量集中的编号；参数3-cmd...
    }
    return semid;
}

int Sem_P(sem_t semid)
{
    //sops有三种方式，0-默认阻塞、IPC_NOWAIT-非阻塞、SEM_UNDO-撤销上一次操作
    struct sembuf sops={0,-1,0};
    return (semop(semid,&sops,1));
}

int Sem_V(sem_t semid)
{
    struct sembuf sops={0,+1,0};
    return (semop(semid,&sops,1));
}

void SetvalueSem(sem_t semid, int value)
{
    union semun sem;
    sem.val = value;
    
    semctl(semid,0,SETVAL,sem);
}

int GetvalueSem(sem_t semid)
{
    union semun sem;
    return semctl(semid,0,GETVAL,sem);
}

void DestroySem(sem_t semid)
{
    union semun sem;
    sem.val = 0;
    semctl(semid,0,IPC_RMID,sem);
}

void Print(char opChar)
{
    int pauseTime;
    srand(getpid());
    int i;

    for(i=0; i<10; i++)
    {
        if(Sem_P(gSemid) != 0)
            ERR_EXIT("Sem_P");
        //临界区-begin
        printf("%c", opChar);
        fflush(stdout);
        pauseTime = rand()%3;
        sleep(pauseTime);
        printf("%c", opChar);
        fflush(stdout);
        //临界区-end
        Sem_V(gSemid);
        pauseTime = rand()%2;
        sleep(pauseTime);
    }
}
#define DELAY (rand()%5+1)

void waitFor2Fork(int phiNum)
{
    int ret = 0;
    int left = phiNum;//哲学家左侧 筷子编号
    int right = (phiNum+1)%5;
    struct sembuf buf[2] = {
        {left, -1, 0},
        {right, -1, 0}
    };
    //同时拿起左侧右侧的筷子，则不会发生死锁
    //如果没有被释放，则等待
    ret = semop(gSemid, buf, 2);
    if(-1 == ret)
    {
        ERR_EXIT("waitFor2Fork");
    }
}
void free2Fork(int phiNum)
{
    int left = phiNum;//哲学家左侧 筷子编号
    int right = (phiNum+1)%5;
    struct sembuf buf[2] = {
        {left, +1, 0},
        {right, +1, 0}
    };
    //同时放下筷子
    semop(gSemid, buf, 2);
}

void waitForLeftFork(int phiNum)
{
    int ret = 0;
    int left = phiNum;//哲学家左侧 筷子编号
    int right = (phiNum+1)%5;
    struct sembuf buf = {left, -1, 0};
    //同时拿起左侧右侧的筷子，则不会发生死锁
    //如果没有被释放，则等待
    ret = semop(gSemid, &buf, 1);
    if(-1 == ret)
    {
        ERR_EXIT("waitForLeftFork");
    }
}
void waitForRightFork(int phiNum)
{
    int ret = 0;
    int left = phiNum;//哲学家左侧 筷子编号
    int right = (phiNum+1)%5;
    struct sembuf buf = {right, -1, 0};
    //同时拿起左侧右侧的筷子，则不会发生死锁
    //如果没有被释放，则等待
    ret = semop(gSemid, &buf, 1);
    if(-1 == ret)
    {
        ERR_EXIT("waitForRightFork");
    }
}
void freeLeftFork(int phiNum)
{
    int left = phiNum;//哲学家左侧 筷子编号
    int right = (phiNum+1)%5;
    struct sembuf buf = {left, +1, 0};
    //同时放下筷子
    semop(gSemid, &buf, 1);
}
void freeRightFork(int phiNum)
{
    int left = phiNum;//哲学家左侧 筷子编号
    int right = (phiNum+1)%5;
    struct sembuf buf = {right, +1, 0};
    //同时放下筷子
    semop(gSemid, &buf, 1);
}
//#define LOCK
void Philosopher(int phiNum)
{
#ifdef LOCK
    for(;;)//有锁
    {
        printf("%d is thinking\n",phiNum);
        sleep(DELAY);
        printf("%d is hungry\n",phiNum);
        waitFor2Fork(phiNum);
        printf("%d is eating\n",phiNum);
        sleep(DELAY);
        free2Fork(phiNum);
    }
#else
    for(;;)//无锁
    {
        printf("%d is thinking\n",phiNum);
        sleep(DELAY);
        printf("%d is hungry\n",phiNum);
        waitForLeftFork(phiNum);
        sleep(5);
        waitForRightFork(phiNum);
        printf("%d is eating\n",phiNum);
        sleep(DELAY);
        freeLeftFork(phiNum);
        freeRightFork(phiNum);
    }
#endif
}

int main(void)
{
    char i;
    key_t key;
    int value = 0;
    int pid;
    int phiNum = 0;
        
    key = ftok("./ipc", 'c');
    gSemid = CreateSem(key,1, 5);//5个信号量都初始化为1，表示可用的状态

    for(int i=1; i<5; i++)
    {
        pid = fork();
        if(-1 == pid)
            ERR_EXIT("fork");
        if(0 == pid)//子进程
        {
            phiNum = i;
            break;
        }
    }

    Philosopher(phiNum);
    
    return 0;
}