使用mmap实现自己的PIPE

程序没有仔细测试，如果有BUG请留言，谢谢！

//pipe.h#ifndef __HEAD_H#define __HEAD_H#define BUFSIZE 4000//读写标志typedef enum{READ,WRITE}RDWRFLAG;//缓冲区和控制标志typedef struct {char buf[BUFSIZE];int head;int tail;int existnum;//缓冲区中存在待读取的数据的个数pid_t rpid;pid_t wpid;} PIPE;//创建自己的PIPEint createPipe(PIPE** pip);//设置进程的读写标志，每个进程要么只读，要么只写void setRDWRflag(PIPE *pip, RDWRFLAG flag);//每次从缓冲区中读取一个byte的数据int readAbye(PIPE* pip, int* c);//每次向缓冲区中写入一个byte的数据int writeAbye(PIPE* pip, int c);//从缓冲区中读取数据int readPipe(PIPE *pip, char *buf, int size);//向缓冲区中写入数据int writePipe(PIPE *pip, const char *buf, int size);//销毁自己的PIPEint closePipe(PIPE *pip);#endif

 

//pipe.c//使用mmap实现父子进程间通信#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/mman.h>#include <sys/types.h>#include "pipe.h"//创建共享区int createPipe(PIPE** pip){*pip=(PIPE*)mmap(NULL, sizeof(PIPE), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0 );if( MAP_FAILED==*pip ){perror("mmap");return -1;}(*pip)->head=0;(*pip)->tail=0;(*pip)->existnum=0;return 0;}//设置调用进程的读写属性，一个进程要么是读，要么是写void setRDWRflag(PIPE* pip, RDWRFLAG flag){if( READ==flag ){pip->rpid=getpid();}else{pip->wpid=getpid();}}//从共享缓冲区中读取一个数据int readAbye(PIPE* pip, int* c){if( 0==pip->existnum )//当缓冲区为空时，返回读错误{return -1;}else{*c=(pip->buf)[pip->head];(pip->existnum)--;if( ++(pip->head)==BUFSIZE ){pip->head=0;}return 0;}}//向共享缓冲区中写入一个数据int writeAbye(PIPE* pip, int c){//缓冲区已满，无法写入if( BUFSIZE==pip->existnum ){return -1;}else{(pip->buf)[pip->tail]=c;(pip->existnum)++;if( BUFSIZE==++(pip->tail) ){pip->tail=0;}return 0;}}int readPipe(PIPE* pip, char* buf, int size){int i=0;int cnt=size;int c;if( getpid()!=pip->rpid ){return -1;}while( cnt-- ){if( -1!=readAbye(pip, &c) ){buf[i++]=c;}else{break;}}if( cnt==0 ){return size;}else{return i;}}int writePipe(PIPE* pip, const char* buf, int size){int i=0;int cnt=size;if( getpid()!=pip->wpid ){return -1;}while( cnt-- ){if( -1==writeAbye(pip, buf[i++]) ){break;}}if( 0==cnt ){return size;}else{return i;}}int closePipe(PIPE* pip){return munmap(pip, sizeof(PIPE));}//测试代码int main(int argc, char *argv[]){char srcbuf[20]="Hello World!";char desbuf[20];memset(desbuf, 0, 20);pid_t pid;PIPE* pip=NULL;if( -1==createPipe(&pip) ){printf("createPipe error!/n");exit(1);}pid=fork();if( pid<0 ){perror("fork");exit(1);}else if( pid==0 )//设置子进程为写端{setRDWRflag(pip, WRITE);if( -1==writePipe(pip, srcbuf, 20) ){printf("writePipe error!/n");exit(1);}exit(0);}else//设置父进程为读端{sleep(1);setRDWRflag(pip, READ);if( -1==readPipe(pip, desbuf, 20) ){printf("readPipe error!/n");exit(1);}printf("%s/n", desbuf);}closePipe(pip);exit(0);}