.TITLE	TRUNC

; SUBROUTINE TO TRUNCATE TRAILING BLANKS FROM A STRING, AND ENSURE
; THAT THE STRING ENDS WITH A NULL.
;
;	CALL TRUNC (S,L)  OR
;	CALL TRUNC (S)
;
;	S IS A STRING
;	L IS LENGTH
;
	.GLOBL	TRUNC

TRUNC:	MOV	2(R5),R0	;ADDRESS STRING
	CMP	@R5,#1		;>1 ARGUMENT?
	BGT	TWOARG
T1:	CLR	R1
1$:	INC	R1		;COUNT
	TSTB	(R0)+		;LOOK FOR NULL
	BNE	1$
	BR	T2

TWOARG:	MOV	@4(R5),R1	;GET COUNT
	BLE	T1		;ZERO OR -: SAME AS 1-ARG
	ADD	R1,R0		;POINT TO END OF STRING
	CLRB	-1(R0)		;BE SURE OF NULL IF NO BLANKS

T2:	DEC	R1		;COUNT STRING BACKWARDS
	BLT	DONE
	TSTB	-(R0)		;ALREADY NULL?
	BEQ	T2
	CMPB	@R0,#40		;NON-BLANK?
	BNE	DONE
	CLRB	@R0		;BLANK- NULL IT
	BR	T2

DONE:	RTS	PC
	.END