.MCALL	.MODULE
.MODULE	ITLOCK,VERSION=04,COMMENT=<ITLOCK/SYSLIB>,IDENT=No,LIB=Yes

; 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.
	.SBTTL	Module Declarations

	.NLIST
	.ENABL	LC
	.DSABL	GBL
	.NLIST	CND
	.LIST
; ++
; FACILITY:
;
;    RT-11 System Subroutine Library
;
; ENVIRONMENT:
;
;    This routine can be used by any job running concurrently in
;    a multi-job environment.
;
; INCLUDE FILES:
;

	; SYSMAC.SML		; RT-11 system macro library.

	.MCALL	.TLOCK		; TLOCK programmed request.

;
; EXTERNAL REFERENCES:
;

	.GLOBL	$ERRP0		; Entry point to EMT error conversion routine.
	.GLOBL	$SYSLB		; Include system library work area.
	.SBTTL	ITLOCK - Fortran-callable Routine

; ++
; FUNCTIONAL DESCRIPTION:
;
;    The ITLOCK function is used in a multi-job  environment  to  attempt
;    to  gain  ownership  of the USR.  It is similar to LOCK in that,  if
;    successful, the calling job returns with the USR in memory. However,
;    if a job attempts to LOCK the USR while another job is using it, the
;    requesting job is suspended  until the USR is free.  With ITLOCK, if
;    the  USR is not available, control returns immediately and the  lock
;    failure is indicated.
;    
; CALLING SEQUENCE:
;
;    i = ITLOCK( )
;
; OUTPUT PARAMETERS:
;
;    R0	     -	USR lock status
;
; RETURNED FUNCTION VALUE:
;
;    0	     -	no error locking USR access for current job
;    1	     -	USR is already in use
;
; --

	.PSECT	SYS$I

ITLOCK::

	.TLOCK			; Attempt to lock USR for exclusive access
				; and use by calling job.
	CALLR	$ERRP0		; Get and convert any errors (status in R0)
				; and return to caller with status in R0.

	.END