//-------------------------------------------------------------------
//	mndlbrot.cpp
//
//	This is a graphics program to display the Mandelbrot set.
//
//	References: 
//	   James Gleick, "Chaos: Making a New Science," 
//		Penguin Press (1987), pp. 231-232.
//	   Roger T. Stevens, "Fractal Programming in C,"
//		M&T Books (1989), p. 255. 
//
//	programmer: ALLAN CRUSE
//	written on: 05 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) 

unsigned char *vram = (unsigned char*)VRAM_BASE_ADDRESS; 
const int display_mode = 0x4103, hres = 800, vres = 600; 

int	max_iterations = 64;
int	max_colors = 8;
float	max_size = 5.0;

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 ); 
}

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 ); 
}


void plot_fractal_set( float mag  )
{
	for (int v = 0; v < vres; v++)
	for (int h = 0; h < hres; h++)
		{
		float	a = (float)(h - hres/2);
		float	b = (float)(vres/2 - v);
		a /= mag;
		b /= mag;
		int	color = -2;
		float	x = 0.0, y = 0.0;
		float	xsquare = 0.0, ysquare = 0.0;
		while (( color < max_iterations )
			&&( xsquare + ysquare < max_size ))
			{
			xsquare = x*x;
			ysquare = y*y;
			y *= x;
			y += y + b;
			x = xsquare - ysquare + a;
			++color;
			}		
		vram[ v*hres + h ] = ( color % max_colors );
		}
}


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 ); 
	getchar(); 
	
	float	magnification = 240.0;
	plot_fractal_set( magnification ); 
	getchar();
	
	system( " mode3 3 " ); 
	tcsetattr( 0, TCSAFLUSH, &otty ); 
}