Re: API parm confusion

["Bruce Vining" <bvining@xxxxxxxxxx>]

This seems to work (using both the supplied buffer and returned pointer):

       PROCESS NOMONOPRC.
       IDENTIFICATION DIVISION.
       PROGRAM-ID. GETPATH.
       ENVIRONMENT DIVISION.
       CONFIGURATION SECTION.
         SOURCE-COMPUTER. IBM-AS400.
         OBJECT-COMPUTER. IBM-AS400.
         SPECIAL-NAMES.
         LINKAGE TYPE PROCEDURE FOR "Qp0lGetPathFromFileID".
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  FILE-ID             PIC X(16)
                   VALUE X'0000000000000001843E02D800004C26'.
       01  PATH-BY-BUFFER      PIC X(1024).
       01  PATH-SIZE           PIC S9(09) BINARY VALUE 1024.
       01  PATH-POINTER        POINTER.
       LINKAGE SECTION.
       01  PATH-BY-POINTER     PIC X(1024).
       PROCEDURE DIVISION.
       MAIN-LINE.
           CALL "Qp0lGetPathFromFileID"
                       USING     BY REFERENCE PATH-BY-BUFFER,
                                 BY VALUE     PATH-SIZE,
                                 BY REFERENCE FILE-ID
                       GIVING                 PATH-POINTER.
           IF PATH-POINTER = NULL
              DISPLAY "Error on file id access",
              STOP RUN.
           DISPLAY "Buffer: " PATH-BY-BUFFER.
           SET ADDRESS OF PATH-BY-POINTER TO PATH-POINTER.
           DISPLAY "Pointer: " PATH-BY-POINTER.
           STOP RUN.

Bruce




                      qsrvbas@netscape.n
                      et (Tom Liotta)           To:       
cobol400-l@midrange.com
                      Sent by:                  cc:
                      cobol400-l-admin@m        Subject:  API parm confusion
                      idrange.com


                      06/13/2002 02:25
                      PM
                      Please respond to
                      cobol400-l





I'm trying to call the Qp0lGetPathFromFileID API and having amazingly
minimal success. I've tried every way I can think of and I get a null
pointer every time. I even tried the example code from PID (or whatever
they're called now) once I understood what it was attempting to do and
after I'd modified it to be more correct. (And I e-mailed my changes back
to them first, asking if they thought I made the right changes and they
definitely agreed.)

>From the UNIX-type APIs manual, the function prototype is:


   char *Qp0lGetPathFromFileID(char *buf, size_t size,
                               Qp0lFID_t fileid);


buf
    (Output)  A pointer to a buffer that will be used to
    hold an absolute path name of the file identified by fileid.

size
    (Input)  The number of bytes in the buffer buf.

fileid
    (Input)  The identifier of the file whose path name is to be returned.


That seems so simple... but a couple thing throw me.

First, the full description of buf includes "The buffer must be large
enough to contain the full path name including the terminating NULL
character." Since I don't know what the path name is until after the API
returns, how can I know how large buf should be?

Second, buf is described as being both 'output' and 'pointer'. What does
that mean? If I pass a pointer, is the API going to change it ('output')?
If so, how do I associate it with the "buf" that I've somehow managed to
make "...large enough to contain the full path name including the
terminating NULL character"? The only thing that makes minimal sense is a
LINKAGE item that I've set ADDRESS OF to null.

Is there sense to be made of this in COBOL?

Much TIA for any light that can be shed on this.

Tom Liotta


--
Tom Liotta
The PowerTech Group, Inc.
19426 68th Avenue South
Kent, WA 98032
Phone  253-872-7788
Fax    253-872-7904
http://www.powertechgroup.com



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