//-------------------------------------------------------------------
//	intwatch.cpp
//
//	This application continuously reads the volatile kernel data
//	that is stored in a pseudo-file (named '/proc/activity') and
//	displays it on the screen until the <ESCAPE> key is pressed.
//	The 'data' consists of an array of 256 counters representing
//	invocations of the kernel's 256 interrupt service routines.
//	
//	NOTE: The counters may be reset by pressing the <SPACE> key.
//
//	Before running this program you must compile and install our 
//	accompanying 'activity.c' kernel module.	
//
//	programmer: ALLAN CRUSE
//	written on: 23 MAR 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()

int main( int argc, char **argv )
{
	// open the pseudo-file for read and write access
	char	filename[] = "/proc/activity";
	int	fd = open( filename, O_RDWR );
	if ( fd < 0 ) { perror( filename ); exit(1); }

	// preserve the current terminal settings 
	struct termios	save_tty;
	tcgetattr( STDIN_FILENO, &save_tty );

	// setup the terminal for noncanonical mode
	struct termios	work_tty = save_tty;
	work_tty.c_lflag &= ~( ICANON | ECHO );
	work_tty.c_cc[ VMIN ] = 1;
	work_tty.c_cc[ VTIME ] = 0;
	tcsetattr( STDIN_FILENO, TCSANOW, &work_tty );	

	// erase the display, hide the cursor. and draw title 	
	printf( "\e[H\e[J" );		// clear the screen
	printf( "\e[?25l\e[?1c" );	// cursor invisible
	printf( "\e[%d;%dH INTERRUPT ACTIVITY MONITOR ", 3, 27 );
	for (int i = 0; i < 16; i++)
		{
		int	row, col;
		col = 7, row = i+7;
		printf( "\e[%d;%dH%02X:", row, col, i*16 );
		row = 6, col = i*4 + 13;
		printf( "\e[%d;%dH%X", row, col, i );
		}

	
	// main program loop uses 'select' for multiplexed input
	int	done = 0;
	while ( !done )
		{
		// use 'select()' to sleep until new input is available 
		fd_set	readset;
		FD_ZERO( &readset );
		FD_SET( STDIN_FILENO, &readset );
		FD_SET( fd, &readset );
		if ( select( 1+fd, &readset, NULL, NULL, NULL ) < 0 ) break;

		// process new input from keyboard
		if ( FD_ISSET( STDIN_FILENO, &readset ) )
			{
			int	inch = 0;
			if ( read( STDIN_FILENO, &inch, 4 ) > 0 )
				{
				lseek( fd, 0LL, SEEK_SET );
				if ( inch == 0x1B ) done = 1;
				else if ( inch == 0x20 ) write( fd, &inch, 1 );
				}
			}

		// process new input from pseudo-file
		if ( FD_ISSET( fd, &readset ) )
			{
			unsigned long	counter[ 256 ] = {0};
			lseek( fd, 0LL, SEEK_SET );
			if ( read( fd, counter, 1024 ) < 1024 ) break;
			for (int i = 0; i < 256; i++)
				{
				int	row = ( i / 16 ) + 7;
				int	col = ( i % 16 ) * 4 + 11;
				int	what = counter[ i ] % 1000;
				if ( !counter[ i ] ) 
					printf( "\e[%d;%dH---", row, col );
				else printf( "\e[%d;%dH%03d", row, col, what );
				}
			printf( "\e[%d;%dH", 24, 0 );	
			}

		fflush( stdout );
		}

	printf( "\e[?25h\e[?0c" );	// restore visible cursor
	printf( "\e[%d;%dH", 24, 0 );	// place cursor at bottom
	tcsetattr( STDIN_FILENO, TCSAFLUSH, &save_tty );	
	close( fd );			// close the pseudo-file
}