rdos/kernel/char.asm

section .data

conbx	dw 7

section .text

	; raw console output
	; IN	dl	character
conout	mov al, dl
	mov ah, 0x0e
	mov bx, [cs:conbx]
	int 0x10
	ret

	; check if character has characters ready
	; OUT	al	0xFF if data, 0 if none
const	mov ah, 1
	int 0x16
	jz .emp
	mov ax, 0xFF
	ret
.emp	mov al, 0
	ret

	; read character from console
	; OUT	al	character or zero
conin	call const
	test al, al
	jz .ret
	mov al, 0
	int 0x16
.ret	ret

	; dummy: write to auxillary dev
auxout	ret

	; dummy: read from auxillary dev
auxin	mov al, 0x1A
	ret

	; dummy: lister out
lstout	ret

	; character input with echo
	; OUT	al	character
getc	call const
	test al, al
	jz getc
	call conin
	push ax
	mov dl, al
	call putc
	pop ax
	ret

	; character input without echo
readc	call const
	test al, al
	jz readc
	jmp conin

	; character output
	; IN	dl	character
putc	jmp conout

	; direct console I/O
	; IN	dl	character to output or 0xFF if input
	; OUT	al	character to read
dcon	cmp dl, 0xFF
	je conin
	jmp conout

	; output character string
	; IN	ds:dx	far ptr to string, '$'-terminated
puts	push si
	mov si, dx
.loop	lodsb
	cmp al, '$'
	je .ret
	mov dl, al
	call putc
	jmp .loop
.ret	pop si
	ret

	; send a beep ctl to console
beep	mov dl, 0x07
	jmp conout

	; buffered input
	; IN	ds:dx	far ptr to buffer
gets	mov si, dx
	mov cx, [si]
	mov ch, 0
	; ch = actual number of chars
	; cl = maximum number of chars
.loop	call readc
	cmp al, 0x0D
	je .cr
	cmp al, 0x08
	je .bs
	cmp al, 0x20
	jc .loop
	; check if there is space in the buffer
	; emit a beep if not
	mov dl, cl
	dec dl
	cmp ch, dl
	jc .append
	call beep
	jmp .loop
	; append to buffer
.append	mov bh, 0
	mov bl, ch
	mov [si+2+bx], al
	inc ch
	mov dl, al
	call putc
	jmp .loop
	; handle backspace
.bs:	test ch, ch
	jz .loop
	mov dl, 0x08
	call putc
	mov dl, 0x20
	call putc
	mov dl, 0x08
	call putc
	dec ch
	jmp .loop
	; handle carriage return
.cr	mov bx, 0
	mov bl, ch
	mov [si+2+bx], al
	mov [si], cx
	mov dl, 0x0A
	call putc
	mov dl, 0x0D
	call putc
	ret