Re: Calling an ILE C Routine from ILE RPG (V7R2)

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

Hello,

Based on the code that you point us to on GitHub, you should not need to 
null-terminate the first parameter ("PW_BUF" in your prototype.)   You 
also should not define options(*String).

What options(*string) does is make a copy of your input parameter with 
x'00' appended.  This isn't right in this case because you want to use 
the PW_BUF parameter for output, and if the C code changes a copy of 
your string, you'll never see the output.

If you look at how the code accesses 'buf' (the name the C code uses for 
your PW_BUF is 'buf').  It does not expect it to have a null at the end, 
it merely replaces its contents, and it will manually add the x'00' at 
the end.

So what you're doing here is correct -- except that you will need to 
call %STR afterwards to remove the null from the result.  For example:

     Dresult           s             64a   varying
         .
         .
     C                   MOVE      64            PW_SIZE
     C                   MOVE      3             PW_FLAGS
     C                   CALLP     PW_RAND ( PW_BUF: PW_SIZE: PW_FLAGS: 
*null )
     C
     C                   eval      result = %str(%addr(PW_BUF))

The %STR simply makes a copy of the data up to the x'00' in PW_BUF, and 
puts the copy in "result" in my example.

Good luck


On 5/22/2020 4:34 AM, Patrik Schindler wrote:
> Hello,
>
> I've ported https://github.com/tytso/pwgen to the CL environment (not PASE!), for easy generation of random characters. and calling the resulting *PGM runs fine.
>
> There's one function (pw_rand) I want to call from RPG, by linking (binding) all (necessary) *MODULE objects from pwgen together with the RPGLE module containing the mainline to one *PGM. I'm *not* talking about a service program.
>
> The C prototype is: void pw_rand(char *buf, int size, int pw_flags);
>
> What I expect it to do: I pass a struct predetermined by the existing C code, stating I want to create a 64 char password with the password flags 3. The password buffer is apparently preallocated by RPG (see debug output below), since it's filled with *BLANKs. The function runs and places a (most likely zero-teminated) string into the buffer: 64 bytes password, 1 byte '00'X. I made the buffer a bit larger to be on the safe side. I also looked up proper field sizes in IBM documentation and that seems correct.
>
> That's what I did in positional RPG:
>
> DPW_BUF           S             70A
> DPW_SIZE          S             10I 0
> DPW_FLAGS         S             10I 0
>   *
> DPW_RAND          PR                  EXTPROC('pw_rand')
> D PW_BUF                        70A
> D PW_SIZE                       10I 0 VALUE
> D PW_FLAGS                      10I 0 VALUE
>   *----------------
> C                   MOVE      64            PW_SIZE
> C                   MOVE      3             PW_FLAGS
> C                   CALLP     PW_RAND ( PW_BUF : PW_SIZE : PW_FLAGS )
>
> ( I hope, my MUA will not mess up with the formatting.)
>
> Compiles and links fine, but when I try to run the call, the application crashes with MCH 3601 (Pointer not set for location referenced.). I read some articles in the net about it but I can't find out where or what I do wrong.
>
> Debug:
>
> PW_BUF                CHAR(70)             '                                                                      '
>                        VALUE IN HEX         '40404040404040404040404040404040404040404040404040404040404040404040404040404040'X
>                          41                 '404040404040404040404040404040404040404040404040404040404040'X
> PW_FLAGS              ZONED(1,0)           3.               'F3'X
> PW_SIZE               ZONED(2,0)           64.              'F6F4'X
>
> Help greatly appreciated! Please refrain from "do it with RPG free", because I don't want to open yet another task on my already big stack. (Learning free is on my list, for a later point in time.)
>
> :wq! PoC
>
> PGP-Key: DDD3 4ABF 6413 38DE - https://www.pocnet.net/poc-key.asc