; number to print in decimal is in R3.
; it will be positive.

; The way DIV works is as follows:
; input R3, R4
; out R0-quotient, R1-remainder

; PUSH
; IN:R0, OUT:R5 (0-success, 1-fail/overflow)
; R3: STACK_END R4: STACK_TOP

; POP
; OUT: R0, OUT R5 (0-success, 1-fail/underflow)
; R3 STACK_START R4 STACK_TOP

.ORIG x3000

	AND R4, R4, #0			; set up R4
	ADD R4, R4, #10

	MAIN_LOOP
		JSR DIV

		AND R3, R3, #0
		ADD R3, R0, #0		; Store quotient back into R3

		AND R0, R0, #0		; put the value of R1-remainder onto R0
		ADD R0, R1, #0		; and then push it onto stack
		JSR PUSH

		ADD R3, R3, #0		; set nzp bits for R3

		BRp MAIN_LOOP		; if quotient is not zero, keep looping


	TOP_OF_PRINT_LOOP
		JSR POP

		ADD R5, R5, #-1		; if nothing was left to pop, we're done
		BRz DONE

		LD R1, ASCII_0		; add ascii offset of '0'
		ADD R0, R0, R1

		OUT			; print

		BR TOP_OF_PRINT_LOOP	; next value in stack

DONE
	HALT


ASCII_0 .FILL x30
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;input R3, R4
;out R0-quotient, R1-remainder
DIV
	AND R0, R0, #0			; Clear R0, R1, and R2
	AND R1, R1, #0
	AND R2, R2, #0

	ADD R1, R1, R3			; R1 holds R3
	NOT R2, R4			; R2 holds negative R4
	ADD R2, R2, #1

	TOP_OF_DIVISION_LOOP
		ADD R1, R1, R2		; Subtract the value of R3
		BRp POSITIVE
		BRn NEGATIVE
		BRz ZERO

	POSITIVE
		ADD R0, R0, #1		; Increment quotient result
		BR TOP_OF_DIVISION_LOOP
	NEGATIVE
		ADD R1, R1, R4		; Bring the remainder back to a positive result
		BR DIV_DONE
	ZERO
		ADD R0, R0, #1		; Increment quotient result
		BR DIV_DONE		; Since the divison was clean,
					; nothing else needs to be done

DIV_DONE
	RET

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;IN:R0, OUT:R5 (0-success, 1-fail/overflow)
;R3: STACK_END R4: STACK_TOP
;
PUSH
	ST R3, PUSH_SaveR3	;save R3
	ST R4, PUSH_SaveR4	;save R4
	AND R5, R5, #0		;
	LD R3, STACK_END	;
	LD R4, STACk_TOP	;
	ADD R3, R3, #-1		;
	NOT R3, R3		;
	ADD R3, R3, #1		;
	ADD R3, R3, R4		;
	BRz OVERFLOW		;stack is full
	STR R0, R4, #0		;no overflow, store value in the stack
	ADD R4, R4, #-1		;move top of the stack
	ST R4, STACK_TOP	;store top of stack pointer
	BRnzp DONE_PUSH		;
OVERFLOW
	ADD R5, R5, #1		;
DONE_PUSH
	LD R3, PUSH_SaveR3	;
	LD R4, PUSH_SaveR4	;
	RET


PUSH_SaveR3	.BLKW #1	;
PUSH_SaveR4	.BLKW #1	;


;OUT: R0, OUT R5 (0-success, 1-fail/underflow)
;R3 STACK_START R4 STACK_TOP
;
POP
	ST R3, POP_SaveR3	;save R3
	ST R4, POP_SaveR4	;save R3
	AND R5, R5, #0		;clear R5
	LD R3, STACK_START	;
	LD R4, STACK_TOP	;
	NOT R3, R3		;
	ADD R3, R3, #1		;
	ADD R3, R3, R4		;
	BRz UNDERFLOW		;
	ADD R4, R4, #1		;
	LDR R0, R4, #0		;
	ST R4, STACK_TOP	;
	BRnzp DONE_POP		;
UNDERFLOW
	ADD R5, R5, #1		;
DONE_POP
	LD R3, POP_SaveR3	;
	LD R4, POP_SaveR4	;
	RET


POP_SaveR3	.BLKW #1	;
POP_SaveR4	.BLKW #1	;
STACK_END	.FILL x3FF0	;
STACK_START	.FILL x4000	;
STACK_TOP	.FILL x4000	;

.END