//-------------------------------------------------------------------
//	studydac.cpp
//
//	This testbed lets us see the effect of modifying the values 
//	that get programmed into the 256 DAC color-table registers.
//
//	programmer: ALLAN CRUSE
//	written on: 12 NOV 2003
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for close() 
#include <termios.h>	// for tcgetattr(), tcsetattr() 
#include <sys/mman.h>	// for mmap() 
#include <sys/io.h>	// for iopl() 

#define VRAM_BASE_ADDRESS 0xA0000000 
#define VGA_MEMORY_LENGTH ( 4 << 20) 

typedef struct	{ unsigned char	r, g, b; } rgb_t;
rgb_t	color_table[ 256 ] = {0};

unsigned char *vram = (unsigned char*)VRAM_BASE_ADDRESS; 
const int display_mode = 0x4101, hres = 640, vres = 480; 

void draw_rectangle( int x, int y, int h, int v, int color ) 
{
	int	minx = x, miny = y, maxx = x+h-1, maxy = y+v-1; 

	do { vram[ y*hres + x ] = color; ++x; } while ( x < maxx ); 
	do { vram[ y*hres + x ] = color; ++y; } while ( y < maxy ); 
	do { vram[ y*hres + x ] = color; --x; } while ( x > minx ); 
	do { vram[ y*hres + x ] = color; --y; } while ( y > miny ); 
}

void draw_color_grid( void )
{
	int	wide = hres/16, high = vres/16;

	for (int i = 0; i < 256; i++)
		{
		int	r = i / 16, k = i % 16;
		unsigned char	*where = &vram[ r*high*hres + k*wide ];	
		for (r = 5; r < high-5; r++) for (k = 5; k < wide-5; k++) 
			where[ r*hres + k ] = i;
		}
}

void set_color_registers( rgb_t *table )
{
	for (int i = 0; i < 256; i++)
		{
		outb( i, 0x3C8 );
		outb( table[ i ].r, 0x3C9 );	
		outb( table[ i ].g, 0x3C9 );	
		outb( table[ i ].b, 0x3C9 );	
		}
}

int map_system_memory( int base, int size ) 
{
	int	fd = open( "/dev/vram", O_RDWR ); 
	if ( fd < 0 ) { perror( "/dev/vram" ); return -1; } 
	int	prot = PROT_READ | PROT_WRITE; 
	int	flag = MAP_FIXED | MAP_SHARED; 
	void	*mm = (void*)base; 
	if ( mmap( mm, size, prot, flag, fd, 0 ) == MAP_FAILED ) 
		{ perror( "mmap" ); return -1; } 
	close( fd ); 
}


int main( int argc, char **argv )
{
	if ( iopl( 3 ) ) { perror( "iopl" ); exit(1); }
	system( "/sbin/insmod vram.o" ); 
	map_system_memory( VRAM_BASE_ADDRESS, VGA_MEMORY_LENGTH ); 

	struct termios	otty; 
	tcgetattr( 0, &otty ); 
	struct termios	tty = otty; 
	tty.c_lflag &= ~( ICANON | ECHO | ISIG ); 
	tty.c_cc[ VMIN ] = 1; 
	tty.c_cc[ VTIME ] = 0; 
	tcsetattr( 0, TCSAFLUSH, &tty ); 

	char	command[ 40 ]; 
	sprintf( command, " clear ; mode3 %d ", display_mode ); 
	system( command ); 

	int	color = 15; 
	draw_rectangle( 0, 0, hres, vres, color ); 
	draw_color_grid();
	getchar();

	// design a new array of color values 
	int	b = 0, g = 64, r = 128, w = 192;
	for (int i = 0; i < 64; i++)
		{
		color_table[ r + i ].r = i;
		color_table[ g + i ].g = i;
		color_table[ b + i ].b = i;
		color_table[ w + i ].r = i;
		color_table[ w + i ].g = i;
		color_table[ w + i ].b = i;
		}	
	set_color_registers( color_table );
	getchar();
	
	system( " mode3 3 " ); 
	tcsetattr( 0, TCSAFLUSH, &otty ); 
}