Implement ramdisk i/o, advance kernel printf

lib/printf.inc

@@ -0,0 +1,80 @@
+printf:
+  cld
+  pop si
+  push bp
+  mov bp, sp
+.loop:
+  mov al, [cs:si]
+  inc si
+  cmp al, 0x00
+  je .end
+  cmp al, 0x25
+  je .handle_25h
+.literal:
+  call putc
+  jmp .loop
+.end:
+  pop bp
+  push si
+  ret
+.handle_25h:
+  mov al, [cs:si]
+  inc si
+  cmp al, 0x25
+  je .literal
+  cmp al, 0x58 ; 'X'
+  je .printhex
+  cmp al, 0x55 ; 'U'
+  je .printdec
+  cmp al, 0x53 ; 'S'
+  je .printstr
+  mov al, 0x3F
+  jmp .literal
+.printhex:
+  add bp, 2
+  mov ax, [bp]
+  mov bx, 0x0010
+  call print_number
+  jmp .loop
+.printdec:
+  add bp, 2
+  mov ax, [bp]
+  mov bx, 0x000A
+  call print_number
+  jmp .loop
+.printstr:
+  add bp, 2
+  mov ax, [bp]
+  call print_string
+  jmp .loop
+
+print_number:
+  xor dx, dx
+  div bx ; ax = dx:ax / 10, dx = dx:ax % 10
+  and ax, ax
+  jz .print
+  push dx
+  call print_number
+  pop dx
+.print:
+  mov al, dl
+  add al, 0x30
+  cmp al, 0x3A
+  jl .noadj
+  add al, 0x07
+.noadj:
+  call putc
+  ret
+
+print_string:
+  push si
+  mov si, ax
+.loop:
+  lodsb
+  cmp al, 0x00
+  je .end
+  call putc
+  jmp .loop
+.end:
+  pop si
+  ret