vbr: implement file searching in rootdir

lib/print.asm

@@ -0,0 +1,66 @@
+; important functions in this file: kprintf
+
+; write a character to kernel output
+; in: al
+printc:
+  push ax
+  push bx
+  mov bx, 0x0000
+  mov ah, 0x0e
+  int 0x10
+  pop bx
+  pop ax
+  ret
+
+; prints a nibble in hex
+; in: al
+print4:
+  and al, 0x0F
+  add al, 0x30
+  cmp al, 0x3a
+  jl printc
+  add al, 0x07
+  jmp printc
+
+; print a byte
+; in: al
+print8:
+  push ax ; avoid destroying ah
+  aam 16 ; high nibble moved into ah
+  xchg ah,al ; high nibble first
+  call print4
+  xchg ah,al
+  call print4
+  pop ax
+  ret
+
+; print a word
+; in: ax
+print16:
+  xchg ah,al
+  call print8
+  xchg ah,al
+  call print8
+  ret
+
+; print a inline following its call opcode
+; the string ends with a nullbyte
+; trashes si
+print_inline:
+  pop si
+  push ax
+  push bx
+  mov bx, 0x0000
+.loop:
+  lodsb
+  cmp al, 0x00
+  je .end
+  mov ah, 0x0e
+  int 0x10
+  cmp al, 0x0D
+  jmp .loop
+.end:
+  pop bx
+  pop ax
+  push si
+  ret