有限状态机实现文件拷贝
通过有限状态机实现文件相互拷贝
示例:relay.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#define FILE1 "/tmp/out1"
#define FILE2 "/tmp/out2"
#define BUFFSIZE 1024
enum fsmstate //状态机状态
{
STATE_R,
STATE_W,
STATE_EX,
STATE_T
};
struct fsm_st //状态机结构体
{
enum fsmstate state;
int sfd;
int dfd;
int lenth;
int pos;
char *err;
char buff[BUFFSIZE];
};
static void fsm_driver(struct fsm_st *fsm) //状态机驱动函数
{
int ret;
switch(fsm->state) //状态判断
{
case STATE_R: //读状态
fsm->lenth = read(fsm->sfd,fsm->buff,BUFFSIZE);
if(fsm->lenth<0)
{
if(errno == EAGAIN)
fsm->state = STATE_R;
else
{
fsm->err = "read";
fsm->state = STATE_EX;
}
}
else if(fsm->lenth == 0)
fsm->state = STATE_T;
else
{
fsm->pos =0;
fsm->state = STATE_W;
}
break;
case STATE_W: //写状态
ret = write(fsm->dfd,fsm->buff + fsm->pos,fsm->lenth);
if(ret <0)
{
if(errno == EAGAIN)
fsm->state = STATE_W;
else
{
fsm->err = "write";
fsm->state = STATE_EX;
}
}
else
{
fsm->pos +=ret;
fsm->lenth -=ret;
if(fsm->lenth ==0)
fsm->state = STATE_T;
fsm->state = STATE_W;
}
break;
case STATE_EX: //出错
fprintf(stderr,"%s\n",fsm->err);
fsm->state = STATE_T;
break;
case STATE_T: //完成
break;
default:
abort();
break;
}
}
static void relay(int fd1, int fd2)
{
struct fsm_st fsm12,fsm21;
int fd1_save,fd2_save;
fd1_save = fcntl(fd1,F_GETFL); //保存文件flag
fsm12.state = STATE_R; //设置初始状态
fsm12.sfd = fd1;
fsm12.dfd = fd2;
fd2_save = fcntl(fd2,F_GETFL);
fsm21.state = STATE_R;
fsm21.sfd = fd2;
fsm21.dfd = fd1;
while(fsm12.state != STATE_T || fsm21.state != STATE_T) //启动状态机
{
fsm_driver(&fsm12);
fsm_driver(&fsm21);
}
fcntl(fd1,F_SETFL,fd1_save);
fcntl(fd2,F_SETFL,fd2_save);
}
int main()
{
int fd1,fd2;
fd1 = open(FILE1,O_RDWR|O_NONBLOCK); //状态机非阻塞打开
if(fd1 <0)
{
perror("open()");
exit(1);
}
fd2 = open(FILE2,O_RDWR|O_NONBLOCK);
if(fd2 <0)
{
perror("open()");
exit(1);
}
relay(fd1,fd2);
close(fd1);
close(fd2);
exit(0);
}