ref: a39ae178fcc4387fe63efea4d15b34d52f4a13de
dir: /os/boot/puma/cga.c/
#include "u.h" #include "lib.h" #include "mem.h" #include "dat.h" #include "io.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 uchar cgaregr(int index) { outb(0x3D4, index); return inb(0x3D4+1) & 0xFF; } static void cgaregw(int index, int data) { outb(0x3D4, index); outb(0x3D4+1, data); } static void movecursor(void) { cgaregw(0x0E, (pos/2>>8) & 0xFF); cgaregw(0x0F, pos/2 & 0xFF); CGASCREENBASE[pos+1] = Attr; } static void cgascreenputc(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(); } void screeninit(void) { if(screeninitdone == 0){ pos = cgaregr(0x0E)<<8; pos |= cgaregr(0x0F); pos *= 2; screeninitdone = 1; } } void cgascreenputs(char* s, int n) { if(screeninitdone == 0) screeninit(); while(n-- > 0) cgascreenputc(*s++); }