keyboard.asm

	; Keyboard library
	; NAMESPACE: "keyboard"
	; REQUIRES: "string"
	keyboard:

; ### ### ### ### ### ### ### ### ### ### ### ### ### ### ###
; ### MACRO: "getKey"
	;
	; return:
	;	ah = BIOS scan code
	;	al = ASCII character
	;	(flag) zf = clear if key available, set otherwise
macro keyboard.getKey
{
	mov		ah, 0x10			; 0x16 - get enhanced keyboard character
	int		0x16
}


; ### ### ### ### ### ### ### ### ### ### ### ### ### ### ###
; ### PROC: "waitForKey"
	;
	; return:
	;	ah = BIOS scan code
	;	al = ASCII code
macro keyboard.waitForKey {
	.waitForKey:
		keyboard.getKey
		cmp		ax, 0
		jz		.waitForKey
		
	.waitForKey.return:
		ret
}
	

; ### ### ### ### ### ### ### ### ### ### ### ### ### ### ###
; ### PROC: "inputString"
	; Catches input from the keyboard into a string. Terminated when ENTER pressed.
	;
	; param:
	;	al = maximum string length, excluding null terminator
	;	ah = 0: no echo, 1: echo (via string.teletype)
	;	di = pointer to new string destination
	; return:
	;	di = pointer to new string, null terminated
macro keyboard.inputString {
	.inputString:
		push	ax
		push	bx
		push	cx
		push	di
		push	dx
		
		mov		cl, al				; hold AX values elsewhere - will be destroyed by .getKey
		mov		ch, 0				; cx = number of characters to get
		mov		bl, ah				; bl = echo flag
		mov		dx, di				; save start of pointer in dx
	
	.inputString.getNextKey:
		call	.waitForKey
		cmp		al, 0x0D			; enter key pressed? stop accepting input and return string
		je		.inputString.appendTerminator
		cmp		al, 0x08			; backspace key pressed? clear previous character
		je		.inputString.backspace
		mov		[di], al			; store character
		inc		di
		
		cmp		bl, 0				; echo enabled?
		jz		.inputString.nextIteration
									; loopz doesn't want to work for some reason? always decrements cx by 2.
									; loopnz is horribly broken, too. infinite loop.
		
		string.putChar				; display character on screen
		
	.inputString.nextIteration:
		loop	.inputString.getNextKey
	
	.inputString.appendTerminator:
		mov		al, 0
		mov		[di], al
		
	.inputString.return:
		pop		dx
		pop		di
		pop		cx
		pop		bx
		pop		ax
		ret
		
	.inputString.backspace:
		cmp		dx, di				; beginning of string?
		je		.inputString.getNextKey
									; act like nothing ever happened
		
									; else...
		dec		di					; previous position in buffer
		
		cmp		bl, 0				; echo enabled?
		jz		.inputString.offsetCounter
		string.putChar				; backspace cursor
		mov		al, ' '
		string.putChar				; blank that character
		mov		al, 0x08
		string.putChar				; and backspace again
		
	.inputString.offsetCounter:
		inc		cx
		jmp		.inputString.getNextKey
}