// a software tty 2 tty null modem

// this is basicly the same as
// http://david.fries.net/utilities/pty2pty.php

// exept:
// - it doesn't change terminal settings



#include <sys/select.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>



void fatalerror(const char *msg1, const char *msg2, int code){
    fprintf(stderr, "%s: %s\n", msg1, msg2);
    exit(code);
}

void fatalsyserror(char *msg){
    fatalerror(msg, strerror(errno), 1);
}

void usage(char *me){
    fprintf(stderr, "%s <term1> <term2>\n", me ? me : "sterm");
}

void writebuf(char *buffer, int bytes, int to){
    while (bytes) {
	int rv = write(to, buffer, bytes);
	if (-1 == rv) { fatalsyserror("write error"); }
	bytes -= rv;
	buffer += rv;
    }
}

void hexify(char *in, char *out, int bytes){
    char table[] = "0123456789ABCDEF";
    while (bytes){
	*out++ = table[(*in >> 8) & 0x0f];
	*out++ = table[*in & 0x0f];
	in++;
	bytes--;
    }
}

void writebuf_hexified(char *buffer, int bytes, int to){
    char bbuffer[bytes*2];
    hexify(buffer, bbuffer, bytes);
    writebuf(bbuffer, bytes*2, to);
}

void transfer(int from, int to){
    int bufsize = 4096;
    char buffer[bufsize];
    int rv;
    int bytes = read(from, buffer, bufsize);
    if (0 == bytes) { exit(0); } // EOF
    if (-1 == bytes) { fatalsyserror("read error"); }

    writebuf(buffer, bytes, to);
}




int main(int argc, char **argv){
    if (argc != 3) { usage(argv[0]); exit(1); }

    int fd1 = open(argv[1], O_RDWR);
    if (-1 == fd1) { fatalsyserror(argv[1]); }

    int fd2 = open(argv[2], O_RDWR);
    if (-1 == fd2) { fatalsyserror(argv[2]); }

    int fdmax = ((fd1>fd2) ? fd1 : fd2) + 1;

    while(1){
	// struct timeval tv = {0,0};
	fd_set inset;

	FD_ZERO(&inset);
	FD_SET(fd1, &inset);
	FD_SET(fd2, &inset);

	if (-1 == select(fdmax, &inset, NULL, NULL, NULL)){
	    fatalsyserror("select()");
	}

	if (FD_ISSET(fd1,  &inset)){ transfer(fd1, fd2); }
	else if (FD_ISSET(fd2, &inset)){ transfer(fd2, fd1); }
    }

    
}