Re: user space -- RPG400-L

Does anybody has a sample program that write data to user space?  I've
written several apps to retrieve data from it but has never try to write
data to it.

I use pointers to access user spaces. To read them, you base a pointer onthe appropriate spot in the user space, and read the data from a variable.To write, you change the value of that variable.

Aside from the pointer logic (which is the same whether you're reading orwriting) the only difference is whether you make a change to the variableor not. Since you already know how to assign values to variables, you maynot need sample code?

Did a bit research and it seems like QUSCHGUS is the only api that allow
me to change the data in user space.

Well, you can change it via a pointer, so I guess indirectly, the QUSPTRUSAPI lets you change data in a user space.

You sound surprised that there aren't more APIs that let you change a userspace, and I'm not sure that I understand why. How many APIs do you need?Is there something you can't do with the existing one? There's also onlyone API that lets you read a user space (QUSRTVUS), why would writing bedifferent?

If that is the case, how does the user space header get formatted? Howcan QUSCHGUS api guarantee each entry in the user space are the samelength

User spaces have no notions of "entries" or "lengths". A user space islike one big huge data area. The difference is that a data area can onlybe 2000 bytes long, whereas a user space can be 16 million bytes long.Otherwise, they're very similar.

A user space has no built-in notion of "headers" or "entries" or"lengths". It's one big long mass of data.

Your program can choose to write blocks of data that have particularlengths. And you can choose to write a block of data that describes theother blocks that you might call a "header". The user space doesn't knowthat they're there, however. To the user space, it's all just a bigmass of bytes. It has no clue what those bytes mean -- that's up to theprogram(s) to worry about.

Are you trying to create a user space that's interpreted by an API orsomething that needs a header? If so, make a BASED data structure thatcontains all of the header fields. Then, get a pointer to the user soace,and base the data structure on it. Finally, fill in the fields of thedata structure (using a series of EVAL statements) so that the headercontains the right data. Presto, you have a header! Though, again, Iquestion why you'd want to do that, unless you're comminicating with someIBM software that requires it.