IBM AS/400 manual Omitting Parameters, Passing Prototyped Parameters, the length of the parameter

Passing Prototyped Parameters

are then built by the calling procedure and passed as hidden para called procedure. Operational descriptors will not be built for omitt

You can retrieve information from		an operational descriptor						using the
APIs Retrieve Operational Descriptor Information (CEEDOD) and Get Descr
Information	About a String Argument (CEESGI).
Note that	operational descriptors	are	only	allowed		for	bound		calls. Fu
non-prototyped calls, an error message will				be	issued		by	the	compiler
operation	code extender is specified		on	a	CALL	operation.

Figure 66 shows an example of the keyword OPDESC.

*-------------------------------------------------------------

*Len returns a 10-digit integer value. The parameter

*is a character string passed by read-only reference.

*Operational descriptors are required so that Len knows

*the length of the parameter.

*OPTIONS(*VARSIZE) is required so that the parameter can

*be less than 32767 bytes.

	*-------------------------------------------------------------
D Len					PR	10I 0 OPDESC
D						32767A	OPTIONS(*VARSIZE) CONST
Figure	66.		Requesting Operational Descriptors for a Prototyped Procedure
For an		example		of	how to use operational descriptors see “Sample Serv
Program”		on	page 94.			The example	consists of a service program which
character			strings		which are passed to it to their hexadecimal equi
service		program uses				operational descriptors to determine the length
acter	string			and	the	length to	be converted.

Omitting Parameters

When

calling

a

procedure,

you may sometimes want

to

leave

out

a

par

may

be that it is not relevant

to the called procedure. For

exampl

might

arise

when

you

are

calling

the

ILE

bindable APIs.

Another reas

that

you

are calling an older procedure

that does

not

handle

this

eter.

If

you need to omit a parameter on a call, you have two c

¹

Specify

OPTIONS(*OMIT)

and

pass

*OMIT

¹

Specify

OPTIONS(*NOPASS) and do not pass the parameter.

The

primary

difference

between

the

two

methods

has

to

do with

how

see

if a parameter has been omitted. In either case, an omitted

be

referenced

by

the called

procedure; if it is, unpredictable

the

called

procedure is designed to handle different

numbers

of

pa

will

have to check for the number of

parameters

passed.

If

*OMIT

'count'

as

a

parameter.

Chapter 10. Calling Programs and Procedures139