//-------------------------------------------------------------------
//	pcxphoto.cpp
//
//	This Linux program must be run from a 'text mode' console.
//	It will display the truecolor image stored in a .pcx file.
//
//	 compile using:  $ g++ pcxphoto.cpp int86.cpp -o pcxphoto
//
//	programmer: ALLAN CRUSE
//	written on: 01 SEP 2003
//	revised on: 25 AUG 2005 -- replace 'mode3' with 'int86()' 
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <unistd.h>	// for read() 
#include <stdlib.h>	// for exit() 
#include <sys/mman.h>	// for mman() 
#include "int86.h"	// for init8086(), int86()
#include "pcx.h"	// for PCX_FILE_HEADER

#define VRAM_BASE_ADDRESS 0xA0000000

typedef unsigned long PEL;
PEL *fb = (PEL*)VRAM_BASE_ADDRESS;

int 	vesa_mode = 0x4121, hres = 640, vres = 480;
char	devname[] = "/dev/vram";
char	pcxname[] = "issxmas.pcx";
struct vm86plus_struct	vm;

void draw_rectangle( int x, int y, int h, int v, PEL color );
void fill_rectangle( int x, int y, int h, int v, PEL color );

int main( int argc, char **argv )
{
	PCX_FILE_HEADER	pcxHeader; 

	// read the .pcx image-file's header 
	int	fd = open( pcxname, O_RDONLY );
	if ( fd < 0 ) { perror( pcxname ); exit(1); }
	if ( read( fd, &pcxHeader, sizeof( pcxHeader ) ) < 0 )
		{ perror( "read" ); exit(1); } 

	// verify the file-format parameters
	if (( pcxHeader.manuf != 10 )||( pcxHeader.rle != 1 ))
		{ fprintf( stderr, "unsupported file-format\n" ); exit(1); }

	// allocate storage for the uncompressed image 
	int	wide = pcxHeader.x2 - pcxHeader.x1;
	int	high = pcxHeader.y2 - pcxHeader.y1;
	int	bytes_per_scanline = pcxHeader.bplin;
	int	npixels = wide * high;
	int	*image = (int*)calloc( npixels, sizeof( PEL ) );
	if ( !image ) { perror( "calloc" ); exit(1); }

	// read and uncompress the .pcx file's image data
	int	i = 0;
	while ( i < npixels )
		{
		int	datum = 0;
		read( fd, &datum, 1 );
		if ( datum < 0xC0 ) image[ i++ ] = datum;
		else	{
			int	reps = datum & 0x3F;
			read( fd, &datum, 1 );
			do { image[ i++ ] = datum; } while ( --reps > 0 );
			}	
		}

	// read the image-file's colors 
	unsigned char	rgb[ 768 ];
	lseek( fd, -768, SEEK_END );
	read( fd, rgb, 768 );
	
	// build the color lookup-table
	PEL	colortable[ 256 ];
	for (i = 0; i < 256; i++)
		{
		PEL	color = 0;
		color |= ( rgb[ 3*i + 0 ] << 16 );	// red intensity
		color |= ( rgb[ 3*i + 1 ] <<  8 );	// green intensity	
		color |= ( rgb[ 3*i + 2 ] <<  0 );	// blue intensity
		colortable[ i ] = color;
		}

	// report some image-file statistics
	printf( "\ngraphic image filename: \'%s\' ", pcxname );
	printf( "\nimage size (in pixels): wide=%d high=%d ", wide, high );
	printf( "\n\n" );
	getchar();
	
	// map the vram device's display-memory into user-space
	int	dd = open( devname, O_RDWR );
	if ( dd < 0 ) { perror( devname ); exit(1); }	
	int	size = (2 << 20);  // 2 megabytes 	
	int	prot = PROT_READ | PROT_WRITE;
	int	flag = MAP_FIXED | MAP_SHARED;
	void	*mm = (void*)VRAM_BASE_ADDRESS;
	if ( mmap( mm, size, prot, flag, dd, 0 ) == MAP_FAILED )
		{ perror( "mmap" ); exit(1); }

	// enter graphics mode 
	init8086();
	vm.regs.eax = 0x4F02;
	vm.regs.ebx = vesa_mode;
	int86( 0x10, vm );
	if ( vm.regs.eax != 0x004F ) 
		{
		fprintf( stderr, "cannot set mode %04X \n", vesa_mode );
		exit(1);
		}
	
	// draw red and green screen borders
	PEL	red = 0xFF0000, green = 0x00FF00;
	int	x = 0, y = 0, h = hres, v = vres;
	draw_rectangle( x, y, h, v, red );	// outer border
	x += 8; y += 8; h -= 16; v -= 16;
	draw_rectangle( x, y, h, v, green );	// inner border
	getchar();

	// draw color lookup-table grid
	int	xindent = ( hres - 160 )/2, yindent = ( vres - 160 )/2;
	for (i = 0; i < 256; i++)
		{
		x = xindent + (i % 16)*10;
		y = yindent + (i / 16)*10;
		fill_rectangle( x, y, 8, 8, colortable[ i ] );
		}
	getchar();

	// write the uncompressed image to display memory
	xindent = ( hres - wide )/2; yindent = ( vres - high )/2;
	for (i = 0; i < npixels; i++)
		{
		x = xindent + (i % bytes_per_scanline);
		y = yindent + (i / bytes_per_scanline);
		fb[ y*hres + x ] = colortable[ image[i] ];
		}
	getchar();

	// restore the video display system to standard text mode
	vm.regs.eax = 0x0003;
	int86( 0x10, vm );
	printf( "\n" );
}

void draw_rectangle( int x, int y, int h, int v, PEL color )
{
	int	minx = x, maxx = x+h-1, miny = y, maxy = y+v-1;
	
	do { fb[ y*hres + x ] = color; ++x; } while ( x < maxx );
	do { fb[ y*hres + x ] = color; ++y; } while ( y < maxy );
	do { fb[ y*hres + x ] = color; --x; } while ( x > minx );
	do { fb[ y*hres + x ] = color; --y; } while ( y > miny );
}

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

	for (y = miny; y <= maxy; y++)
		for (x = minx; x <= maxx; x++)
			fb[ y*hres + x ] = color;
}