Tranz Am: Routine at 7170

7170: Mask Sprite

Used by the routines at ActorEraseMovedSprite, ActorEraseDestroyed, 7149, DrawTwoBytes and 71CB.
MaskSprite	7170	LD A,C	Jump to 71CB if the vertical position is zero.
	7171	AND A
	7172	JR Z,$71CB
	7174	DEC C	Decrease C by one.
	7175	PUSH HL	Stash HL on the stack.
	7176	LD A,($5E40)	B=5E40.
	7179	LD B,A	B=5E40.
	717A	EX DE,HL
	717B	PUSH DE
	717C	LD D,(HL)
	717D	INC HL
	717E	LD E,(HL)
	717F	INC HL
	7180	AND A
	7181	JR Z,$716D
	7183	EX DE,HL
	7184	XOR A
MaskSprite_0	7185	ADD HL,HL
	7186	ADC A,A
	7187	DJNZ MaskSprite_0
	7189	EX DE,HL
	718A	EX (SP),HL
	718B	CPL
	718C	AND (HL)
	718D	LD (HL),A
	718E	INC L
This entry point is used by the routine at 716D.
MaskSprite_1	718F	LD A,D
	7190	CPL
	7191	AND (HL)
	7192	LD (HL),A
	7193	INC L
	7194	LD A,E
	7195	CPL
	7196	AND (HL)
	7197	LD (HL),A
	7198	POP DE
	7199	POP HL
	719A	CALL ScreenPos1PixelAbove	Call ScreenPos1PixelAbove.
	719D	EXX
	719E	LD A,C
	719F	AND A
	71A0	JR Z,DrawTwoBytes_0
This entry point is used by the routine at 71CB.
MaskSprite_2	71A2	DEC C
	71A3	PUSH HL
	71A4	LD A,($5E41)	B=5E41.
	71A7	LD B,A	B=5E41.
	71A8	EX DE,HL
	71A9	PUSH DE	Stash DE on the stack.
	71AA	LD D,(HL)
	71AB	INC HL
	71AC	LD E,(HL)
	71AD	INC HL
	71AE	AND A
	71AF	JR Z,$71EA
	71B1	EX DE,HL
	71B2	XOR A
MaskSprite_3	71B3	ADD HL,HL
	71B4	ADC A,A
	71B5	DJNZ MaskSprite_3
	71B7	EX DE,HL
	71B8	EX (SP),HL
	71B9	OR (HL)
	71BA	LD (HL),A
	71BB	INC L