//-------------------------------------------------------------------
//	vramdraw.cpp
//
//	This application exercises services of our 'vram.c' driver.
//
//	programmer: ALLAN CRUSE
//	written on: 19 NOV 2004
//	revised on: 13 DEC 2004 -- correction to draw_pixel() bounds
//-------------------------------------------------------------------

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

char devname[] = "/dev/vram";
int	hmax = 1280;
int	vmax = 1024;
int	fd;

void draw_pixel( int r, int c, int color )
{
	if (( r < 0 )||( r >= vmax )) return;
	if (( c < 0 )||( c >= hmax )) return;
	
	int	pos = ( hmax * r + c ) << 2;
	lseek( fd, pos, SEEK_SET );
	write( fd, &color, 4 );
}

int main( int argc, char **argv )
{
	// install our driver module
	system( "/sbin/insmod vram.o" );

	// open the device-file 
	fd = open( devname, O_RDWR );
	if ( fd < 0 ) { perror( devname ); exit(1); }
	getchar();

	// draw white border around edge of screen
	long	pel = 0x00FFFFFF;
	int	row = 0, col = 0;
	do { draw_pixel( row, col, pel ); } while ( ++col < hmax-1 );
	do { draw_pixel( row, col, pel ); } while ( ++row < vmax-1 );
	do { draw_pixel( row, col, pel ); } while ( --col >      0 );
	do { draw_pixel( row, col, pel ); } while ( --row >      0 );
	getchar(); 

	// fill screen with green color
	pel = 0x0000FF00;
	int	nbytes = hmax * vmax;
	for (int i = 0; i < nbytes; i++) 
		write( fd, &pel, sizeof( pel ) );
	getchar();

	// close the device-file and remove the driver-module
	close( fd );
	system( "/sbin/rmmod vram" );
}