.model tiny
.code
.386
org 100h
entry: jmp start
int9:
    in al, 60h

    mov di, tail
    mov buffer[di], al

    inc tail
    and tail, 0fh

    mov ax, tail
    cmp head, ax

    jne _1

    inc head
    and head, 0fh

_1:
    in al, 61h
    or al, 80h
    out 61h, al

    and al, 07fh
    out 61h, al

    mov al, 20h
    out 20h, al
    iret

buffer          db 10h dup (?)
head            dw ?
tail            dw ?
oldInt9         dd ?
ENDL            db 13, 10, '$'
ESC_SC          db 81h
SPACE_SC        db 039h
spaceMessage    db 'muhaha', '$'

start:
    xor dx, dx
    mov ax, 3509h
    int 21h
    mov word ptr oldInt9,   bx
    mov word ptr oldInt9+2, es

    cli
    mov ax, 2509h
    mov dx, offset int9
    int 21h
    sti

    _2:
        mov di, head
        cmp tail, di
        je _2

        mov dl, buffer[di]
        inc head
        and head, 0fh

        cmp dl, SPACE_SC
        jne _cont

            mov ax, 0900h
            lea dx, spaceMessage
            int 21h

            mov ax, 0900h
            lea dx, ENDL
            int 21h

        _cont:

        cmp dl, ESC_SC
        je exit

		xor bx, bx
		mov bl, dl
		call out_hex
        jne _2

out_hex proc
	push bp
	mov bp, sp

	pusha

	mov cx, 4
	_3:
		rol bx, 4
		mov al, bl
		and al, 0fh
		cmp al, 10
		sbb al, 69h
		das

		mov dh, 02h
		xchg ax, dx
		int 21h
	loop _3

	mov ax, 0900h
	lea dx, ENDL
	int 21h

	popa

	mov sp, bp
	pop bp
	ret
out_hex endp

exit:
    cli
    mov ax, 2509h
    mov dx, word ptr cs:[oldInt9]
    mov ds, word ptr cs:[oldInt9+2]
    int 21h
    sti
ret

end entry