topic Calling C library functions from basic with string parameter in Operating System - OpenVMS

Calling C library functions from basic with string parameter

AlexanderM — Fri, 27 Sep 2013 03:41:52 GMT

Hello to everyone.

The question is:

Is there an simple way to form '\0' terminated c-string in basic to pass it as an argument in C library's function?

Library's function notification:

int login(char * login, char * password);

Re: Calling C library functions from basic with string parameter

AlexanderM — Fri, 27 Sep 2013 04:04:38 GMT

So, the simplest way for me is to create wrapping functions over my library function and transfer a pointer to string for a parsing in C.

But it is not neat-looking solution. Furthermore I've not managed to find how to get a pointer in basic yet.

Re: Calling C library functions from basic with string parameter

Steven Schweda — Fri, 27 Sep 2013 04:52:45 GMT

Re: Calling C library functions from basic with string parameter

AlexanderM — Fri, 27 Sep 2013 05:35:45 GMT

Thanks. It is the exactly what I am looking for). There are only one task: to convince the library's users do not forget add 0 in the end of string.

Re: Calling C library functions from basic with string parameter

Steven Schweda — Fri, 27 Sep 2013 11:37:45 GMT

Re: Calling C library functions from basic with string parameter

Hein van den Heuvel — Sun, 29 Sep 2013 20:07:14 GMT

For sake of completeness...

>> Furthermore I've not managed to find how to get a pointer in basic yet.

Basic has the LOC function to return the address of a variable.

Note: "For dynamic strings, the LOC function returns the address of the descriptor rather than the address of the data."

For a dynamic string you can use LIB$ANALYZE_SDESC to get the actual address, but that gets tedious.

One option is to use a static / fixed string in a MAP, copy in the string , use (left side) MID$ to put a NULL at the desired offset, pass the address of the (fixed) string using LOC.

This may sound like a lot of overhead, but please realize the operations like 'cstr+ "0"c' will also copy the strings around and allocate descriptors and stuff.

Hein.