as24.s

unix v7是最后一个广泛发布的研究型UNIX版本

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/ a4 -- pdp-11 assembler pass 2

oset:
	mov	r2,-(sp)
	mov	r3,-(sp)
	mov	(r5)+,r3
	mov	r1,r2
	bic	$!777,r1
	add	r3,r1
	add	$8,r1
	mov	r1,(r3)+	/ next slot
	mov	r3,r1
	add	$1006,r1
	mov	r1,(r3)+	/ buf max
	mov	r0,(r3)+
	mov	r2,(r3)+	/ seek addr
	mov	(sp)+,r3
	mov	(sp)+,r2
	rts	r5

putw:
	mov	r1,-(sp)
	mov	r2,-(sp)
	mov	(r5)+,r2
	mov	(r2)+,r1	/ slot
	cmp	r1,(r2)		/ buf max
	bhis	1f
	mov	r0,(r1)+
	mov	r1,-(r2)
	br	2f
1:
	tst	(r2)+
	mov	r0,-(sp)
	jsr	r5,flush1
	mov	(sp)+,r0
	mov	r0,*(r2)+
	add	$2,-(r2)
2:
	mov	(sp)+,r2
	mov	(sp)+,r1
	rts	r5

flush:
	mov	(r5)+,r2
	cmp	(r2)+,(r2)+
flush1:
	mov	(r2)+,0f
	mov	(r2)+,r1
	mov	r1,0f+2		/ seek address
	mov	fout,r0
	sys	indir; 9f
	.data
9:	sys	lseek; 0:..; ..; 0
	.text
	bic	$!777,r1
	add	r2,r1		/ write address
	mov	r1,0f
	mov	r2,r0
	bis	$777,-(r2)
	add	$1,(r2)		/ new seek addr
	adc	-(r2)
	cmp	-(r2),-(r2)
	sub	(r2),r1
	neg	r1
	mov	r1,0f+2		/ count
	mov	r0,(r2)		/ new next slot
	mov	fout,r0
	sys	indir; 9f
	jes	wrterr
	.data
9:	sys	write; 0:..; ..
	.text
	rts	r5

wrterr:
	mov	$1,r0
	sys	write; 9f; 8f-9f
	jmp	saexit
9:	<as: write error on output\n>; 8:

readop:
	mov	savop,r4
	beq	1f
	clr	savop
	rts	pc
1:
	jsr	pc,getw1
	cmp	r4,$200
	blo	1f
	cmp	r4,$4000
	blo	2f
	add	$usymtab-4000,r4
	rts	pc
2:
	add	$symtab-1000,r4
1:
	rts	pc

getw:
	mov	savop,r4
	beq	getw1
	clr	savop
	rts	pc
getw1:
	dec	ibufc
	bgt	1f
	movb	fin,r0
	sys	read; inbuf; 512.
	bes	3f
	asr	r0
	mov	r0,ibufc
	bne	2f
3:
	mov	$4,r4
	sev
	rts	pc
2:
	mov	$inbuf,ibufp
1:
	mov	*ibufp,r4
	add	$2,ibufp
	rts	pc