relay2.c

linux源码

#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>

#define BUFSIZE 32

struct job_st {
	int fd1, fd2;
	int fd1save, fd2save;
	int r1, w2, r2, w1;
	char buf12[BUFSIZE], buf21[BUFSIZE];
	int len12, pos12, len21, pos21;
};

int
do_relay(struct job_st *p)
{
	int ret;

	if (p->r1+p->w2+p->r2+p->w1) {
		if (p->r1) {
			p->len12=read(p->fd1, p->buf12, BUFSIZE);
			p->pos12=0;
			if (p->len12==-1) {
				if (errno!=EAGAIN) {
					p->r1=0; p->w2=0;
				}
			} else if (p->len12==0) {
				p->r1=0; p->w2=0;
			} else {
				p->r1=0; p->w2=1;
			}
		}

		if (p->w2) {
			ret=write(p->fd2, p->buf12+p->pos12, p->len12);
			if (ret==-1) {
				if (errno!=EAGAIN) {
					p->r1=0; p->w2=0;
				}
			} else {
				p->pos12+=ret;
				p->len12-=ret;
				if (p->len12==0) {
					p->r1=1; p->w2=0;
				}
			}
		}
/*
		if (r2) {
			len21=read(fd2, buf21, BUFSIZE);
			pos21=0;
			if (len21==-1) {
				if (errno!=EAGAIN) {
					r2=0; w1=0;
				}
			} else if (len21==0) {
				r2=0; w1=0;
			} else {
				r2=0; w1=1;
			}
		}

		if (w1) {
			ret=write(fd1, buf21+pos21, len21);
			if (ret==-1) {
				if (errno!=EAGAIN) {
					r2=0; w1=0;
				}
			} else {
				pos21+=ret;
				len21-=ret;
				if (len21==0) {
					r2=1; w1=0;
				}
			}
		}
*/
	}

	return 0;
}

int
relay(struct job_st *p)
{
	p->fd1save=fcntl(p->fd1, F_GETFL);
	ret=fcntl(p->fd1, F_SETFL, p->fd1save|O_NONBLOCK);
	if (ret==-1) {
		return -1;
	}
	p->fd2save=fcntl(p->fd2, F_GETFL);
	ret=fcntl(p->fd2, F_SETFL, p->fd2save|O_NONBLOCK);
	if (ret==-1) {
		fcntl(p->fd1, F_SETFL, p->fd1save);
		return -1;
	}

	while (1) {
		ret=do_relay(p);
		if (ret==-1) {
			break;
		}
	}
	fcntl(fd1, F_SETFL, fd1save);
	fcntl(fd2, F_SETFL, fd2save);
	return 0;
}

int
main()
{
	int ret;
	int fd1, fd2;

	fd1=open("/dev/tty5", O_RDWR);
	if (fd1==-1) {
		perror("open()");
		exit(1);
	}
	fd2=open("/dev/tty6", O_RDWR);
	if (fd2==-1) {
		perror("open()");
		exit(1);
	}

	write(fd1, "fd1\n", 4);
	write(fd2, "fd2\n", 4);
	ret=relay(fd1, fd2);

	close(fd1);
	close(fd2);

	exit(0);
}