#include "u.h"#include "lib.h"#include "mem.h"#include "dat.h"#include "fns.h" enum {	Width		= 160,	Height		= 25, 	Attr		= 7,		/* white on black */}; #define CGASCREENBASE	((uchar*)KADDR(0xB8000)) static int pos;static int screeninitdone; static ucharcgaregr(int index){	outb(0x3D4, index);	return inb(0x3D4+1) & 0xFF;} static voidcgaregw(int index, int data){	outb(0x3D4, index);	outb(0x3D4+1, data);} static voidmovecursor(void){	cgaregw(0x0E, (pos/2>>8) & 0xFF);	cgaregw(0x0F, pos/2 & 0xFF);	CGASCREENBASE[pos+1] = Attr;} static voidcgascreenputc(int c){	int i; 	if(c == '\n'){		pos = pos/Width;		pos = (pos+1)*Width;	}	else if(c == '\t'){		i = 8 - ((pos/2)&7);		while(i-->0)			cgascreenputc(' ');	}	else if(c == '\b'){		if(pos >= 2)			pos -= 2;		cgascreenputc(' ');		pos -= 2;	}	else{		CGASCREENBASE[pos++] = c;		CGASCREENBASE[pos++] = Attr;	}	if(pos >= Width*Height){		memmove(CGASCREENBASE, &CGASCREENBASE[Width], Width*(Height-1));		memset(&CGASCREENBASE[Width*(Height-1)], 0, Width);		pos = Width*(Height-1);	}	movecursor();} static voidscreeninit(void){	if(screeninitdone == 0){		pos = cgaregr(0x0E)<<8;		pos |= cgaregr(0x0F);		pos *= 2;		screeninitdone = 1;	}} voidcgascreenputs(char* s, int n){	if(screeninitdone == 0)		screeninit();	while(n-- > 0)		cgascreenputc(*s++);}