Add original unix v6

source/s3/get.s

@@ -0,0 +1,92 @@
+/ getw/getc -- get words/characters from input file
+/ fopen -- open a file for use by get(c|w)
+/
+/ calling sequences --
+/
+/   mov $filename,r0
+/   jsr r5,fopen; ioptr
+/
+/  on return ioptr buffer is set up or error bit is set if
+/  file could not be opened.
+/
+/   jsr r5,get(c|w)1; ioptr
+/
+/  on return char/word is in r0; error bit is
+/  set on error or end of file.
+/
+/  ioptr is the address of a 518-byte buffer
+/  whose layout is as follows:
+/
+/  ioptr: .=.+2    / file descriptor
+/         .=.+2    / charact+2    / pointer to next character (reset if no. chars=0)
+/         .=.+512. / the buffer
+
+	.globl	getc,getw,fopen
+
+fopen:
+	mov	r1,-(sp)
+	mov	(r5)+,r1
+	mov	r0,0f
+	sys	0; 9f
+.data
+9:
+	sys	open; 0:..; 0
+.text
+	bes	1f
+	mov	r0,(r1)+
+	clr	(r1)+
+	mov	(sp)+,r1
+	rts	r5
+1:
+	mov	$-1,(r1)
+	mov	(sp)+,r1
+	sec
+	rts	r5
+
+.data
+getw:
+	mov	(r5),9f
+	mov	(r5)+,8f
+	jsr	r5,getc; 8:..
+	bec	1f
+	rts	r5
+1:
+	mov	r0,-(sp)
+	jsr	r5,getc; 9:..
+	swab	r0
+	bis	(sp)+,r0
+	rts	r5
+.text
+
+getc:
+	mov	r1,-(sp)
+	mov	(r5)+,r1
+	dec	2(r1)
+	bge	1f
+	mov	r1,r0
+	add	$6,r0
+	mov	r0,0f
+	mov	r0,4(r1)
+	mov	(r1),r0
+	sys	0; 9f
+.data
+9:
+	sys	read; 0:..; 512.
+.text
+	bes	2f
+	tst	r0
+	bne	3f
+2:
+	mov	(sp)+,r1
+	sec
+	rts	r5
+3:
+	dec	r0
+	mov	r0,2(r1)
+1:
+	clr	r0
+	bisb	*4(r1),r0
+	inc	4(r1)
+	mov	(sp)+,r1
+	rts	r5
+