/ u5 -- unix

mget:
	mov	*u.fofp,mq / file offset in mq
	clr	ac / later to be high sig
	mov	$-8,lsh   / divide ac/mq by 256.
	mov	mq,r2
	bit	$10000,i.flgs / lg/sm is this a large or small file
	bne	4f / branch for large file
	bit	$!17,r2
	bne	3f / branch if r2 greater than or equal to 16
	bic	$!16,r2 / clear all bits but bits 1,2,3
	mov	i.dskp(r2),r1 / r1 has physical block number
	bne	2f / if physical block num is zero then need a new block
		   / for file
	jsr	r0,alloc / allocate a new block
	mov	r1,i.dskp(r2) / physical block number stored in i-node
	jsr	r0,setimod / set inode modified byte (imod)
	jsr	r0,clear / zero out disk/drum block just allocated
2:
	rts	r0
3: / adding on block which changes small file to a large file
	jsr	r0,alloc / allocate a new block for this file; block number
	                 /in r1
	jsr	r0,wslot / set up I/O buffer for write, r5 points to first
			 / data word in buffer
	mov	$8.,r3 / next 6 instructions transfer old physical block
		       / pointers
	mov	$i.dskp,r2 / into new indirect block for the new large file
1:
	mov	(r2),(r5)+
	clr	(r2)+
	dec	r3
	bgt	1b
	mov	$256.-8.,r3 / clear rest of data buffer
1:
	clr	(r5)+
	dec 	r3
	bgt	1b
	jsr	r0,dskwr / write new indirect block on disk
	mov	r1,i.dskp / put pointer to indirect block in i-node
	bis	$10000,i.flgs / set large file bit in i.flgs word of i-node
	jsr	r0,setimod / set i-node modified flag
	br	mget
4: / large file
	mov	$-8,lsh / divide byte number by 256.
	bic	$!776,r2 / zero all bits but 1,2,3,4,5,6,7,8; gives offset
			 / in indirect block
	mov	r2,-(sp) / save on stack
	mov	mq,r2 / calculate offset in i-node for pointer to proper
       		      / indirect block
	bic	$!16,r2
	mov	i.dskp(r2),r1
	bne	2f / if no indirect block exists
	jsr	r0,alloc / allocate a new block