#include "types.h"

#define RAMSCREEN 0xB8000	/* debut de la memoire video */
#define SIZESCREEN 0xFA0	/* 4000, nombres d'octets d'une page texte */
#define SCREENLIM 0xB8FA0

char kX = 0;			/* position courante du curseur a l'ecran */
char kY = 17;
char kattr = 0x0E;		/* attributs video des caracteres a afficher */


/* 
 * 'scrollup' scrolle l'ecran (la console mappee en ram) vers le haut
 * de n lignes (de 0 a 25).
 */
void scrollup(unsigned int n)
{
	unsigned char *video, *tmp;

	for (video = (unsigned char *) RAMSCREEN;
	     video < (unsigned char *) SCREENLIM; video += 2) {
		tmp = (unsigned char *) (video + n * 160);

		if (tmp < (unsigned char *) SCREENLIM) {
			*video = *tmp;
			*(video + 1) = *(tmp + 1);
		} else {
			*video = 0;
			*(video + 1) = 0x07;
		}
	}

	kY -= n;
	if (kY < 0)
		kY = 0;
}

void putcar(uchar c)
{
	unsigned char *video;
	int i;

	if (c == 10) {		/* CR-NL */
		kX = 0;
		kY++;
	} else if (c == 9) {	/* TAB */
		kX = kX + 8 - (kX % 8);
	} else if (c == 13) {	/* CR */
		kX = 0;
	} else {		/* autres caracteres */
		video = (unsigned char *) (RAMSCREEN + 2 * kX + 160 * kY);
		*video = c;
		*(video + 1) = kattr;

		kX++;
		if (kX > 79) {
			kX = 0;
			kY++;
		}
	}

	if (kY > 24)
		scrollup(kY - 24);
}

/*
 * 'print' affiche a l'ecran, a la position courante du curseur, une chaine
 * de caracteres terminee par \0.
 */
void print(char *string)
{
	while (*string != 0) {	/* tant que le caractere est different de 0x0 */
		putcar(*string);
		string++;
	}
}