Parameter list in Assembler

Avinashhlg · New User Joined: 05 Jan 2010 Posts: 7 Location: Bangalore

To accept the data from parameters passed from COBOL program to assembler, we know that R1 will have the address of the parameter, but I have difficulty in identifying the length of the data. How will I able to get the length of parameter passed?

enrico-sorichetti · Posted: Tue Jan 05, 2010 5:09 pm

You will not!
review the LE interlanguage reference for the parameter passing rules

note:
R1 will point to the list of the addresses of the parameters

Robert Sample · Posted: Tue Jan 05, 2010 5:12 pm

Actually, register 1 does not have the address of the parameter -- register 1 has the address of the parameter list. This is a significant difference.

What does this mean?

Avinashhlg · New User Joined: 05 Jan 2010 Posts: 7 Location: Bangalore

Yes, iam referring to the length of the indivisual parameter. Is there any way by which I can extract the exact data passed from the calling program. The problem is that I dont know the length of the data I receive in my assembler code.

PeterHolland · Posted: Tue Jan 05, 2010 5:30 pm

A scenario could be :

UPON ENTRY R1 POINTS TO ADDRESS OF PLIST PLIST+0 : LENGTH OF PARM
PLIST+2 : START OF PARM

Another scenario is :

R1 POINTS TO ADDRESS OF PLIST
PLIST CONTAINS POINTERS TO PARAMETERS WITH LENGTH+DATA
PLIST ENDS WITH X'80',AL3(0)

Avinashhlg · New User Joined: 05 Jan 2010 Posts: 7 Location: Bangalore

I could see only the data in the plist and not length.

enrico-sorichetti · Posted: Tue Jan 05, 2010 5:47 pm

cobol follows the assembler conventions
it' s Your concern to know the structure of the data You are dealing with

just to show a different scenario
in PL/I
with the OPTIONS ASM clause for parameter passing,
PL/I will use the assembler convention ==> data address
without the OPTIONS ASM clause,
PL/I will use it's internal scheme ==> locator descriptor address
where all the info about the variable is kept ( length,type,..., content)

PeterHolland · Posted: Tue Jan 05, 2010 5:47 pm

Maybe there is no length, cause the parameter is always fixed length.
The called routine, and the calling routine MUST know that of course.

But thats a stupid way of supplying parameter lists.

Robert Sample · Posted: Tue Jan 05, 2010 5:48 pm

Pass the length as a parameter.

PeterHolland · Posted: Tue Jan 05, 2010 6:09 pm

www.ibmmainframes.com/post-160331.html

Bill O'Boyle · Posted: Tue Jan 05, 2010 7:19 pm

Although the following discussion is not quite the same, it might be helpful -

www.ibmmainframes.com/viewtopic.php?t=44937&highlight=

Bill

dick scherrer · Posted: Wed Jan 06, 2010 1:01 am

Hello,

If your goal is to write a generic module that will handle "anything" that arrives, i suspect you will expereience considerable frustration. . .

If the data has a structure, use the same in both the calling and called modules and there is no need to determine length.

Why do you believe you need to determine the length dynamically?

Possibly i have misunderstood something. . .

UmeySan · Posted: Thu Jan 07, 2010 3:42 pm

Hi Avinashhlg !

The lengt depends on the structure of the data you would receive.

If there are several structures, the best is, as said before, to define al field at the first point of the structure which contains the length.

Also a field with a FunctionCode would be useful. Several parms indicate several functions.

So, as everyone told before, it's your turn to handle this. If there is nothing that fits your requirement, just create it by yourselfe.