.NLIST	TOC,SYM
.TITLE	$ALBLK
.SBTTL	ULBLIB 025	- Allocate Block
.IDENT	\V01.00\
.PSECT	.LIBC.
.ENABL	LC,GBL

; Copyright (c) 1998 by Mentec, Inc., Nashua, NH.
; All rights reserved
;
; This software is furnished under a license for use only on a
; single computer system and  may  be  copied  only  with  the
; inclusion of the above copyright notice.  This software,  or
; any other copies thereof, may not be provided  or  otherwise
; made available to any other person except for  use  on  such
; system and to one who agrees to these license  terms.  Title
; to  and  ownership of the software shall at all times remain
; in Mentec, Inc.
;
; The information in this document is subject to change without
; notice and should not be construed as a commitment by Digital
; Equipment Corporation, or Mentec, Inc.
;
; Digital and Mentec  assume  no  responsibility for the use or
; reliability of its software on equipment which is not supplied
; by Digital  or Mentec,  and listed  in the  Software  Product
; Description.
;+
; $ALBLK
; This routine determines whether a block of memory storage can be
; allocated from the free dynamic memory.  If so, it clears the allocated
; block and return the resident memory address of the block.  If there is
; insufficient space in the free dynamic memory, the user routine $ERMSG
; is entered with E$R4 in R1 and $FRHD in R2.
;
;	R1	= number of bytes to be allocated (<=512.)
;
;	CALL	$ALBLK
;
;	R0	= dynamic memory address of the cleared block.
;	R1	= 0
;	R2	= random
;
;	If unsuccessful, $ERMSG is jumped to with
;	R1	= E$R4
;	R2	= $FRHD
;-

$ALBLK::
	MOV	R1,-(SP)	;Save the size
	CALL	$GTCOR		;Request a block of storage
	BCC	10$		;Branch if successful
	MOV	#E$R4,R1	;R1 = error code
	MOV	#$FRHD,R2	;R2 -> free memory list head
	JMP	$ERMSG		;Issue fatal error (no return)

10$:	MOV	(SP)+,R1	;Restore the size of the request
	ADD	#3,R1		;Round to next 2 word boundary
	BIC	#3,R1		;Clear ugly bits
	ASR	R1		;Get size in words
	MOV	R0,R2		;Copy address of block
2$:	CLR	(R2)+		;Clear block
	DEC	R1		;Decrement the count
	BNE	2$		;Loop
	RETURN

.END