MS-DOS Protected Mode (DOS/4GW) Test

32dos.c

#include <stdio.h>
#include <dos.h>
#include <conio.h>
#include <string.h>
#include <stdlib.h>

#define STAR_MAX    128
#define STAR_DARK   16
#define STAR_BRIGHT 31
#define STAR_SHIFT  4
#define STAR_SPEED  5

struct Vector {
	int x, y, z;
};

unsigned char *vga_mem = (unsigned char *)0xA0000;
unsigned short *txt_mem = (unsigned short *)0xB8000;

int lin = 0;
int col = 0;

struct Vector stars[STAR_MAX];

void modeswitch(unsigned char mode) {
	_asm {
		mov al, mode
		int 0x10
	}
}

void vsync(void) {
	while(inp(0x03da) & 8) {}
	while(!(inp(0x03da) & 8)) {}
}

unsigned short *output_text(unsigned short *t, char *text, char properties) {
	size_t i;
	size_t length = strlen(text);
	
	for(i = 0; i < length; ++i) {
		if(text[i] == 0x0A) {
			++col;
			lin = 0;
		}
		else if(text[i] == 0x20) {
			++lin;
			if(t)
				++t;
		}
		else {
			++lin;
			if(t)
				*t++ = properties << 8 | text[i];
			else
				txt_mem[col * 80 + lin] = properties << 8 | text[i];
		}
	}
	
	return txt_mem + (col * 80 + lin);
}

float remap(float value, float oldmin, float oldmax, float newmin, float newmax)
{
    float real_range = oldmax - oldmin;
    float new_range = newmax - newmin;
    return (((value - oldmin) * new_range) / real_range) + newmin;
}

void draw_star(struct Vector star) {
	float k, x, y;
	unsigned char col;
	
	star.x >>= STAR_SHIFT; star.y >>= STAR_SHIFT; star.z >>= STAR_SHIFT;
	
	k = 32.0f / star.z;
	x = star.x * k + (320 / 2);
	y = star.y * k + (200 / 2);
	col = (int)remap(star.z, 25, 0, STAR_DARK, STAR_BRIGHT);
	
	if(!(x >= 320 || x <= 0 || y >= 200 || y <= 0))
		vga_mem[(int)y * 320 + (int)x] = col;
}

int main(void) {
	int i;
	unsigned short *t = txt_mem;
	char buf[512];
	size_t size = 64000;
	void *mem = NULL;
	
	srand(0);
	
	memset(t, 0, 4000);
	
	sprintf(buf, "\n\n    size of int is: %d\n", sizeof(int));
	output_text(NULL, buf, 0x07);
	
	if(sizeof(int) == 4) {
		output_text(NULL, "Now we're cooking with gas!!\n\n", 0x82);
		t = output_text(NULL, "    Allocating size:  ", 0x07);
		
		while((mem = malloc(size)) != NULL) {
			sprintf(buf, "%zu KB (%zu MB)", size / 1000, size / 1000000);
			memset(t, 0, 256);
			output_text(t, buf, 0x0F);
			size += 64000;
			free(mem);
		}
	}
	else {
		output_text(NULL, "16-bit real mode it is then...\n", 0x04);
	}
	
	output_text(NULL, "\n\nTime for more stuff?: ", 0x07);
	getch();
	output_text(NULL, "\nGoing into mode 13h!!\n", 0x85);
	
	modeswitch(0x13);
	//replace_pit_interrupt();
	
	do {
		memset(vga_mem + 320 * (rand() % 200), rand(), 320);
		
		vsync();
	} while(!kbhit());
	
	getch();
	
	for(i = 0; i < STAR_MAX; ++i) {
		stars[i].x = ((rand() % 50) - 25) << STAR_SHIFT;
		stars[i].y = ((rand() % 50) - 25) << STAR_SHIFT;
		stars[i].z = ((rand() % 50) - 25) << STAR_SHIFT;
	}
	
	do {	
		memset(vga_mem, 0, 320 * 200);
		for(i = 0; i < STAR_MAX; ++i) {
			stars[i].z -= STAR_SPEED;
			if(stars[i].z < 0) {
				stars[i].z = 25 << STAR_SHIFT;
				stars[i].x = ((rand() % 50) - 25) << STAR_SHIFT;
				stars[i].y = ((rand() % 50) - 25) << STAR_SHIFT;
			}
			
			draw_star(stars[i]);
		}
		
		vsync();
	} while(!kbhit());
	
	modeswitch(0x03);
	//restore_pit_interrupt();
	
	return 0;
}

/*

* タイマーなどの割り込みを置き換えるのは拡張メモリーではめっちゃくちゃ難しくなっちゃうからとりえあず放置


typedef void interrupt (*handler_t)(void);

handler_t old_pit_handler;
long freq_div = 1000;
long prev_slow_tick = 0;
long time_counter = 0;

void interrupt pit_handler(void) {
	long slow_tick;
	
	_asm cli
	
	slow_tick = time_counter * 1193182 / (freq_div * 65536);
	time_counter++;
	
	if(slow_tick != prev_slow_tick){
		prev_slow_tick = slow_tick;
		old_pit_handler();
	}
	else {
		outp(0x20, 0x20);
	}
	
	_asm sti
	
	printf("yos\n");
}

void *selector_to_addr(unsigned short selector, unsigned short offset) {
	union REGS r;
	union SREGS s;
	
	r.x.eax = 0x0006;
	r.x.bx = selector;
	int386(0x31, &r, &r);
	
	return (void *)((r.x.cx << 4 | r.x.dx) + offset);
}

void pm_setvect(handler_t vector) {
	
}

handler_t pm_getvect(void) {
	union REGS r;
	union SREGS s;
	
	r.x.eax = 0x0204;
	r.h.bl = 0x08;
	int386(0x31, &r, &r);
	
	return selector_to_addr((unsigned short)r.x.ecx, (unsigned short)r.x.edx);
}

void replace_pit_interrupt(void) {
	long speed = 1193182 / freq_div;
	
	old_pit_handler = _dos_getvect(0x08);
	
	outp(0x43, 0x36);
	outp(0x40, speed % 0x100);
	outp(0x40, speed / 0x100);
	
	_dos_setvect(0x08, pit_handler);
}

void restore_pit_interrupt(void) {
	outp(0x43, 0x36);
	outp(0x40, 0xFF);
	outp(0x40, 0xFF);
	
	_dos_setvect(0x08, old_pit_handler);
}
*/