//-------------------------------------------------------------------
//	multplex.cpp
//
//	This program illustrates use of the 'select()' function for
//	efficiently performing multiplexed input from two devices.
//
//	programmer: ALLAN CRUSE
//	written on: 23 APR 2005
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for read(), write(), close() 
#include <termios.h>	// for tcgetattr(), tcsetattr()

void handle_nic_input( int );	// prototypes our response to nic
void handle_kbd_input( int );	// prototypes our response to kbd

char devname[] = "/dev/nic";	// name of the device special file
int done = 0;			// flag used for loop-termination

int main( void )
{
	// open the device-file for our network interface
	int	nic = open( devname, O_RDWR );
	if ( nic < 0 ) { perror( devname ); exit(1); }

	// preserve terminal settings and setup noncanonical input
	int	kbd = STDIN_FILENO;
	struct termios	orig_term;
	tcgetattr( kbd, &orig_term );
	struct termios	work_term = orig_term;
	work_term.c_lflag &= ~(ICANON | ECHO);
	work_term.c_cc[ VMIN ] = 1;	// one character at a time
	work_term.c_cc[ VTIME ] = 0;	// with no console timeout
	tcsetattr( kbd, TCSAFLUSH, &work_term );	
	
	// main program-loop performs the multiplexed device-input
	int	maxfd = 1 + (( kbd < nic ) ? nic : kbd );
	do	{
		fd_set	readset;
		FD_ZERO( &readset );
		FD_SET( kbd, &readset );
		FD_SET( nic, &readset );
		if ( select( maxfd, &readset, NULL, NULL, NULL ) < 0 ) break;
		if ( FD_ISSET( kbd, &readset ) ) handle_kbd_input( kbd );
		if ( FD_ISSET( nic, &readset ) ) handle_nic_input( nic );
		}
	while ( !done );

	// restore the original terminal-control settings	
	tcsetattr( kbd, TCSAFLUSH, &orig_term );	
	printf( "\n" );
}



void handle_kbd_input( int kbd )
{
	char 	inch[ 8 ] = {0};
	int	nbytes = read( kbd, inch, sizeof( inch ) );
	if ( *(int*)inch == '\e' ) done = 1;
	else	write( STDOUT_FILENO, &inch, nbytes );
}


void handle_nic_input( int nic )
{
	unsigned char	packet[ 64 ] = {0};
	int 	nbytes = read( nic, packet, sizeof( packet ) );
	if ( nbytes > 0 ) 
		{
		printf( "\n" );
		for (int i = 0; i < nbytes; i += 16)
			{
			printf( "\n%04X: ", i );
			for (int j = 0; j < 16; j++)
				{
				if ( i+j < nbytes ) 
					printf( "%02X ", packet[i+j] );
				else	printf( "   " );
				}
			for (int j = 0; j < 16; j++)
				{
				char	ch = ' ';
				if ( i+j < nbytes ) ch = packet[ i+j ];
				if (( ch < 0x20 )||( ch > 0x7E )) ch = '.';
				printf( "%c", ch ); 
				}
			}
		printf( "\n" );
		}
}