Re: Reg: Fetch Input Data Structure Attributes in DATA-INTO Parser

Suren,

RPG does not currently provide that information to the parser.

That is something that would've been useful to me, too, at times..   so if you were to submit an idea to IBM, I'd be willing to vote for it.

My suggestion would be for IBM to add another routine to the 'environment' that would allow the parser to retrieve details about the variable you are mapping data into.  Ideally, this would NOT just be "the current field" but would allow you to retrieve the entire layout of the variable you're working with, possibly requiring multiple calls?

Conceptually, this would be something like this:

dcl-s v int(10);

dcl-ds info likeds(QrnDiVarInfo_t);


v = QrnDiOpenResultVar(handle);

dou rc <> 0;

  rc = QrnDiReadResultVar(v: handle: Info);

  if rc = 1;

     leave;

  endifl;

  // "info" now contains stuff like the name, type (packed, zoned, varchar, char, etc), length, decimal places, ccsid, maybe other things.  There could also be custom "types" for the dcl-ds and end-ds lines so you can keep track of when your data is nested inside something else, etc.

enddo;

QrnDiCloseResultVar(v);


This would allow the parser to make better decisions in many cases.   For example, if an element is supposed to get a default value from the parser, should it use a *blank or 0 or d'0001-01-01'  No way to know what to pass right now because the parser knows nothing about the variable it's mapping into.

Or suppose the parser wants to implement a feature similar to the "countprefix" feature where there is another field with a prefix tht corresponds to the first field.  Since we have no way to see what is in the data structure, we can't evaluate whether there's a field with a prefix -- meaning the parser is limited in the decisions it can make with what to do with the data.

I don't agree with Jon's assessment that DATA-INTO couldn't do this.  After all, it knows all about the resulting variable at compile-time... there's no reason it couldn't provide this info to the parser somehow.

Same with the generator in DATA-GEN.

-SK

On 9/15/23 7:38 AM, Suren K wrote:

Hi Jon,

I am planning to send some additional parameters in the Parser parameter
section and retrieve the list of fields in the parser parameter that have
the truncation issue.

Regards,
Suren


On Thu, Sep 14, 2023 at 6:44 PM Jon Paris <jon.paris@xxxxxxxxxxxxxx> wrote:

The problem you face is that RPG does not supply that information to the
parser - nor could it really. The parser gives RPG a name and the string
associated with it. RPG then stores it in the DS after conversion if
needed. Even if you could do it (more in a minute) how would you report it
to your RPG program?

I think a better option is to make all the fields varchar of a length
longer than they could be. Then process the data into the real DS checking
length etc as you do so.

The only way I can think of to have the parser validate it is to pass the
parser an extra parm containing an array of all the field names and lengths
of the real DS and use that to validate the length before returning it to
RPG.


Jon P

On Sep 14, 2023, at 4:20 PM, Suren K <suren7437@xxxxxxxxx> wrote:

Hi All,

I am planning to add logic in the DATA-INTO Parser Program, before
populating the value into Data Structure, I need to verify the length of
the fields to validate whether any truncation is happening.

For example

dcl-ds Ds_Input;
name char(5);
number zoned(4:0);
end-ds;

data = '{"name": "David John","number": 123}';
data-into Ds_Input %data(data:dataOption) %parser('mpParser':userParm);

In the above example, the name attribute is the character of length 5 but
the value will be 10 characters. I want to validate this in the Parser
Program.

Is it possible to get the attribute inside the parser program like the
attribute of the field "name" is a character of length 5 and the

attribute

of a field "number" is numeric of length 4 with 0 decimal places when
parsing field by field?

Regards,
Suren
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