//-------------------------------------------------------------------
//	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: user$ make pcxphoto
//
//	NOTE: The following preliminary steps are needed in order
//	to run this program, and may require system administrator 
//	setup (or 'sudo' privileges):
//	(1) device-node '/dev/vram' is created with rw privileges
//		root# mknod /dev/vram c 99 0
//		root# chmod a+rw /dev/vram
//	(2) program 'mode3' (from svgalib) has 'setuid' attribute 
//		root# gcc mode3.c lrmi.c -o mode3
//		root# chmod a+s mode3
//	(3) module 'vram.c' is compiled in current user directory
//		user# make vram.o	
//	Here step 3 may require installing a suitable 'Make' file
//	that specifies the proper Linux kernel 'build' directory. 
//
//	programmer: ALLAN CRUSE
//	written on: 01 SEP 2003
//-------------------------------------------------------------------

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

#define VRAM_BASE_ADDRESS 0xB0000000
#define VESA_DISPLAY_MODE 0x413A

typedef unsigned long PEL;

PEL *fb = (PEL*)VRAM_BASE_ADDRESS;
int 	hres = 640, vres = 480;
char	devname[] = "/dev/vram";
char	pcxname[] = "issxmas.pcx";

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	pcx;
	
	// read the image file's header	
	int	fd = open( pcxname, O_RDONLY );
	if ( fd < 0 ) { perror( pcxname ); exit(1); }
	if ( read( fd, &pcx, sizeof( pcx ) ) < 128 ) 
		{ perror( "read" ); exit(1); }

	// allocate storage for the image data
	int	wide = pcx.x2 - pcx.x1;
	int	high = pcx.y2 - pcx.y1;
	int	npixels = wide * high;
	int	*image = (int*)calloc( npixels, sizeof( int ) );
	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;
		}
	close( fd );

	// report image file statistics
	printf( "\ngraphic image filename: \'%s\' ", pcxname );
	printf( "\nimage size (in pixels): wide=%d high=%d ", wide, high );
	printf( "\n\n" );
	getchar();
	
	// install our 'vram' device-driver module into the Linux kernel  
	system( "/sbin/insmod ./vram.o ; clear" ); 
	// and then map the vram device's display-memory into user-space
	fd = open( devname, O_RDWR );
	if ( fd < 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, fd, 0 ) == MAP_FAILED )
		{ perror( "mmap" ); exit(1); }

	// enter graphics mode 
	char	command[ 40 ] = "";
	sprintf( command, "mode3 %d", VESA_DISPLAY_MODE );	
	system( command );
	
	// 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();

	// draw the uncompressed image
	xindent = ( hres - wide )/2; yindent = ( vres - high )/2;
	for (i = 0; i < npixels; i++)
		{
		x = xindent + (i % pcx.bplin);
		y = yindent + (i / pcx.bplin);
		fb[ y*hres + x ] = colortable[ image[i] ];
		}
	getchar();

	// restore the video display system to standard text mode
 	system( "mode3" );
}

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;
}