#include <unistd.h>
int pipe(int pipefd[2]);
//pipefd：文件描述符數(shù)組，其中pipefd[0]表示讀端，pipefd[1]表示寫端，值為對應(yīng)的文件描述符 
//返回值:成功返回0，失敗返回錯誤代碼

#include <iostream>
#include <cstdio>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <string>
#include <cstring>
#include <cstdlib>

#define N 2
#define NUM 1024
using namespace std;

void Writer(int wfd)
{
	//定義要發(fā)送的字符串
    string s = "this is your child";
    //獲取當(dāng)前進程的pid
    pid_t myid = getpid();
    int number = 0;

    char buffer[NUM];
    while(1)
    {
        //此處相當(dāng)于buffer[0] = '\0';意思是將整個數(shù)組當(dāng)做字符串用并且清空字符串
        buffer[0] = 0;
        //將字符串、pid、以及計數(shù)器number按照"%s-%d-%d"格式寫到buffer當(dāng)中
        snprintf(buffer,sizeof(buffer),"%s-%d-%d",s.c_str(),myid,number++);
        //這里傳過來的wfd為對應(yīng)的文件描述符，然后將buffer中的有效內(nèi)容寫到管道文件緩沖區(qū)中
        write(wfd,buffer,strlen(buffer));

        sleep(5);
    }
}

void Reader(int rfd)
{
    char buffer[NUM];
    while(1)
    {
    	//同上
        buffer[0] = 0;
        //將文件描述符rfd讀取的內(nèi)容存儲到buffer中，并返回讀取到的字符個數(shù)n
        ssize_t n = read(rfd,buffer,sizeof(buffer));
        //如果有內(nèi)容則打印出來
        if(n > 0)
        {
            buffer[n] = 0;
            cout << "parent get a message[" << getpid() << "]# " << buffer << endl;
        }
        //沒有內(nèi)容即讀取完成
        else if(n == 0) 
        {
            printf("parent read file done!\n");
            break;
        }
        //其他情況就是有bug了
        else break;
    }
}

int main()
{
	//pipefd用來存放輸出型參數(shù)
    int pipefd[N] = {0};	
    //成功驗證
    int n = pipe(pipefd);
    if(n < 0)
    {
        return 1;
    }
	//創(chuàng)建子進程
    pid_t id = fork();
	//錯誤情況
    if(id < 0)
    {
        return 2;
    }
    //子進程執(zhí)行段，把讀寫函數(shù)打包一下，寫到一個函數(shù)里，立體分明
    else if(id == 0)
    {
        //child
        //子進程要寫不讀，關(guān)掉pipefd[0]，寫pipefd[1]，寫完再關(guān)掉pipefd[1],然后退出
        close(pipefd[0]);
        Writer(pipefd[1]);
        close(pipefd[1]);
        exit(0);
    }
    //父進程執(zhí)行段
    else{
        //parent
        //父進程要讀不寫，關(guān)掉pipefd[1]，讀pipefd[0]，等待子進程結(jié)束再關(guān)掉pipefd[0]
        close(pipefd[1]);
        Reader(pipefd[0]);

        pid_t rid = waitpid(id,NULL,0);
        if(rid < 0)
        {
            return 3;
        }
        close(pipefd[0]);
    }
    return 0;
}

int main()
{
	//......
    if(id < 0)
    {
        return 2;
    }
    else if(id == 0)
    {
        //child
        close(pipefd[0]);
        Writer(pipefd[1]);
        close(pipefd[1]);
        exit(0);
    }
    else{
        //parent
        close(pipefd[1]);
        Reader(pipefd[0]);
        close(pipefd[0]);
        cout << "father close read fd: " << pipefd[0] << endl;
        sleep(5);
        int status = 0;
        pid_t rid = waitpid(id,&status,0);
        if(rid < 0)
        {
            return 3;
        }
        cout << "wait child success: " << rid << " exit code: " << ((status>>8)&0xFF) << " exit signal: " << (status&0x7F) << endl;
        sleep(5);
        cout << "parent quit" << endl;
    }
    
    return 0;
}

//子進程一直寫
void Writer(int wfd)
{
    string s = "this is your child";
    pid_t myid = getpid();
    int number = 0;

    char buffer[NUM];
    while(1)
    {
        //buffer[0] = '\0';
        buffer[0] = 0;
        snprintf(buffer,sizeof(buffer),"%s-%d-%d",s.c_str(),myid,number++);
        write(wfd,buffer,strlen(buffer));
    }
}

//父進程5秒讀一次數(shù)據(jù)
void Reader(int rfd)
{
    char buffer[NUM];
    while(1)
    {
        sleep(5);
        buffer[0] = 0;
        ssize_t n = read(rfd,buffer,sizeof(buffer));
        if(n > 0)
        {
            buffer[n] = 0;
            cout << "parent get a message[" << getpid() << "]# " << buffer << endl;
        }
        else if(n == 0) 
        {
            printf("parent read file done!\n");
            break;
        }
        else break;
    }
}