/* rotate.c : map a->b, b->c, .. z->a
 *   purpose: useful for showing tty modes
 */

#include	<stdio.h>
#include	<termios.h>
#include	<fcntl.h>
#include	<string.h>
#include	<signal.h>

int main()
{
    int c;

    signal( SIGINT, SIG_IGN );
    signal( SIGTSTP, SIG_IGN );
    signal( SIGQUIT, SIG_IGN );

	tty_mode(0);				/* save current mode	*/
	set_cr_noecho_mode();			/* set -icanon, -echo	*/


    while ( ( c=getchar() ) != EOF ){
        if ( c == 'Q') {
            tty_mode(1);
            exit(0);
        }
        else if ( c == 'z' )  
            c = 'a';
        else if (islower(c))
            c++;
        putchar(c);
    }
}


set_cr_noecho_mode()
/* 
 * purpose: put file descriptor 0 into chr-by-chr mode and noecho mode
 *  method: use bits in termios
 */
{
	struct	termios	ttystate;

	tcgetattr( 0, &ttystate);		/* read curr. setting	*/
	ttystate.c_lflag    	&= ~ICANON;	/* no buffering		*/
	ttystate.c_lflag    	&= ~ECHO;	/* no echo either	*/
	ttystate.c_cc[VMIN]  	=  1;		/* get 1 char at a time	*/
	tcsetattr( 0 , TCSANOW, &ttystate);	/* install settings	*/
}

set_nodelay_mode()
/*
 * purpose: put file descriptor 0 into no-delay mode
 *  method: use fcntl to set bits
 *   notes: tcsetattr() will do something similar, but it is complicated
 */
{
	int	termflags;

	termflags = fcntl(0, F_GETFL);		/* read curr. settings	*/
	termflags |= O_NDELAY;			/* flip on nodelay bit	*/
	fcntl(0, F_SETFL, termflags);		/* and install 'em	*/
}

/* how == 0 => save current mode,  how == 1 => restore mode */
/* this version handles termios and fcntl flags             */

tty_mode(int how)
{
	static struct termios original_mode;
	static int            original_flags;
	if ( how == 0 ){
		tcgetattr(0, &original_mode);
		original_flags = fcntl(0, F_GETFL);
	}
	else {
		tcsetattr(0, TCSANOW, &original_mode); 
		fcntl( 0, F_SETFL, original_flags);	
	}
}