[Info-vax] Access to _all_ VMS system services and library functions from DCL ?

[Arne Vajhøj]

On 7/8/2017 4:09 PM, Simon Clubley wrote:
> On 2017-07-07, Arne Vajhøj <arne at vajhoej.dk> wrote:
>> On 4/4/2017 2:21 PM, Simon Clubley wrote:
>>> This is why there really should be a marshalling system for the types
>>> to convert between the DCL types and the VMS native types so you can
>>> mostly eliminate this problem. This is also part of why the VMS
>>> development process needs an automatic interface generator if you
>>> do this.
>>>
>>> As mentioned in my original post, some aspects might be challenging
>>> in DCL as it stands today. For example, how do you marshall an
>>> itemlist as seen by DCL into an itemlist directly usable by VMS ?
>>>
>>> It would be a lot easier if DCL had a lists within lists data
>>> structure or a lists within an array data structure. As it
>>> stands, you would probably need a new DCL intrinsic to allow
>>> you to manually build a usable itemlist from within DCL.
>>
>> It requires some tweaking, but it is possible.
> 
> Interesting.
> 
> Now we just need a similar process for DCL (or whatever scripting
> language is shipped with VMS in the future).

I doubt DCL will be the language for this.

JavaScript as I am using. Or Python. Or something else
in that category.

> Suggested enhancements in this new future language over the example
> below would be to see the reference to SYS$PUBLIC_VECTORS dropped and
> SYS$GETJPIW to be changed from a string to a function/method name so
> type checking could be done (if the replacement language supported
> type checking to this level). This _may_ also mean the parameter
> access method would not have to be declared in the code is it is below.

Anything is possible.

Original version was primarily to show item lists working:

$ type itmlst.js
importClass(Packages.java.lang.System);

function printf() {
     System.out.printf.apply(System.out, arguments);
}

importClass(Packages.dk.vajhoej.vms.call.VMS);
importClass(Packages.dk.vajhoej.vms.call.VMSLibrary);
importClass(Packages.dk.vajhoej.vms.call.IOSB);
importClass(Packages.dk.vajhoej.vms.call.lib.VMSCodes);

var pid = new VMS.LongWord(0);
var usrnamitm = new VMS.Item32CharacterStringOut(VMSCodes.JPI$_USERNAME, 
256);
var itmlst = new VMS.ItemList32([usrnamitm]);
var iosb = new VMS.Block(new IOSB());

var sts = VMS.call("SYS$PUBLIC_VECTORS",
                    "SYS$GETJPIW",
                    VMS.MISSING,
                    VMS.pass(pid).byReference().readWrite(),
                    VMS.MISSING,
                    VMS.pass(itmlst).byReference().readOnly(),
                    VMS.pass(iosb).byReference().writeOnly(),
                    VMS.MISSING,
                    VMS.MISSING);

printf("sts=%.0f pid=%d usrnam=%s\n", sts, pid.getValue(), 
VMS.createTrimmedString(usrnamitm.getValue()));

$ jsshell itmlst.js
sts=1 pid=1072 usrnam=ARNE

Getting rid of the string image name and function name is trivial:

$ type itmlst2.js
importClass(Packages.java.lang.System);

function printf() {
     System.out.printf.apply(System.out, arguments);
}

importClass(Packages.dk.vajhoej.vms.call.VMS);
importClass(Packages.dk.vajhoej.vms.call.VMSLibrary);
importClass(Packages.dk.vajhoej.vms.call.IOSB);
importClass(Packages.dk.vajhoej.vms.call.lib.VMSCodes);

function SYS$GETJPIW(p1,p2,p3,p4,p5,p6,p7) {
    return 
VMS.call("SYS$PUBLIC_VECTORS","SYS$GETJPIW",p1,p2,p3,p4,p5,p6,p7);
}

var pid = new VMS.LongWord(0);
var usrnamitm = new VMS.Item32CharacterStringOut(VMSCodes.JPI$_USERNAME, 
256);
var itmlst = new VMS.ItemList32([usrnamitm]);
var iosb = new VMS.Block(new IOSB());

var sts = SYS$GETJPIW(VMS.MISSING,
                       VMS.pass(pid).byReference().readWrite(),
                       VMS.MISSING,
                       VMS.pass(itmlst).byReference().readOnly(),
                       VMS.pass(iosb).byReference().writeOnly(),
                       VMS.MISSING,
                       VMS.MISSING);

printf("sts=%.0f pid=%d usrnam=%s\n", sts, pid.getValue(), 
VMS.createTrimmedString(usrnamitm.getValue()));

$ jsshell itmlst2.js
sts=1 pid=1072 usrnam=ARNE

But I don't see the point. For known functions we would want
a much cleaner API - something more DCL lexical like.

$ type itmlst3.js
load("vms.js");

var res = syssrv.SYS$GETJPIW(0,["PID","USERNAME"]);
var sts = res.getStatus();
var pinfo = res.getResult();
printf("sts=%.0f pid=%.0f usrnam=%s\n", sts, pinfo.PID, pinfo.USERNAME);

$ jsshell itmlst3.js
sts=1 pid=1072 usrnam=ARNE

This is a much nicer API. But it does not show the item lists. The
array of item code get translated to an item list in some of the
glue code (Java).

Arne