#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <termios.h>
#include <time.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>

__inline__ unsigned long long int
rdtsc()
{
    unsigned long long int x;
    __asm__ volatile ("rdtsc" : "=A" (x));
    return x;
}


int
main()
{
    int fd;
    int rtm;
    pid_t pid;

    fd = open( "/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);
    if( fd < 0 ){
	fprintf( stderr, "device open error.\n" );
	exit(1);
    }

    pid = fork();
    if( pid == -1 ){
	perror( "fork() error: " );
	exit(1);
    }else if( pid ){ /* parent */
	unsigned long long tsc;
	int arg, lstat;

	while(1){
	    arg = TIOCM_CTS;
	    ioctl( fd, TIOCMIWAIT, arg );
	    tsc = rdtsc();
	    ioctl( fd, TIOCMGET, &lstat );
	    if( lstat & TIOCM_CTS ){
		printf( "> CTS set:   %llu\n", tsc );
	    }else{
		printf( "> CTS clear: %llu\n", tsc );
	    }
	    fflush(stdout);
	}
    }else{ /* child */
	unsigned long long tsc, tsc0;
	int arg;

	while(1){
	    usleep( 500000 );
	    arg = TIOCM_RTS;
	    tsc0 = rdtsc();
	    ioctl( fd, TIOCMBIS, &arg );
	    tsc = rdtsc();
	    printf( "< RTS set:   %llu\n", tsc0 );
	    printf( "< ioctl:     %llu\n", tsc );
	    fflush(stdout);
	    usleep( 500000 );
	    arg = TIOCM_RTS;
	    tsc0 = rdtsc();
	    ioctl( fd, TIOCMBIC, &arg );
	    tsc = rdtsc();
	    printf( "< RTS clear: %llu\n", tsc0 );
	    printf( "< ioctl:     %llu\n", tsc );
	    fflush(stdout);
	}
    }
    
    return 0;
}