_lshiftc_and_add:
; inputs: iy = ptr to src, hl = ptr to dest, a = shift count
; ouputs: none
; destroys: a, b, c, flags
; algorithm:
;		byte shift: shift by between 1 and 32 (inclusive) bytes by:
;			shift a to the right 3x (div 8), then and a with 30 to constrain to 30 or less
;		 	if a == 0, skip to the bit shift section
;			set the first a bytes of de to 0
;			copy 32 - a bytes from hl to de + a
;		bit shift: shift by between 1 and 7 (inclusive) bits by:
;			restore original a, then and with 7 to return a value mod 8
;			return if 0
;			shift the 32 bytes at hl to the left a times
	push af
		srl a
		srl a
		srl a

		or a
		jr z, .skip_byte_shift

		; add a to hl
		ld bc, 0
		ld c, a
		add hl, bc

		; sub 32 - a
		ld b, a
		ld a, 32					; set c to 32
		sub a, b
		ld b, a
	pop af
	push bc
		and a, 7			; and a with 7 to get a % 8
		ld b, a
		ld a, 1
.lshiftc:
		rlca
		djnz .ishiftc
	pop bc		; loop count in b
	ld c, a		; bits multiplier in c
	xor a
.loop_xor_bytes:
	ld e, (iy)
	ld d, c
	mlt de
	add a, e
	xor (hl)
	ld (hl), a
	ld a, d
	inc iy
	inc hl
	djnz .loop_xor_bytes
	ret