COBOL call C function

Give a sample on how COBOL call C function.

Including:

1. C function definition

2. parameter passing, char * pointer, int, null pointer

1. Define C function (myfun.c)

void myfun(const unsigned char mapping[], unsigned char buffer[], unsigned int len)

{

     /* put your codes here*/

}

2. Compile C function into a shared library.

gcc -o myfun.so -shared -fpic myfun.c

3. COBOL caller codes

...

WORKING-STORAGE SECTION.

       01 PARAM1     PIC X(4) VALUES 'AAAA'.

       01 PARAM2     PIC X(4) VALUES 'BBBB'.

       01 PARAM3     PIC 9(4) COMP-5.

       ...

PROCEDURE DIVISION.

       MOVE 4 TO PARAM3.

       MOVE "ABCD" TO PARAM2.

       CALL 'myfun'  USING PARAM1

                                             PARAM2

                        BY VALUE PARAM3.

       MOVE "abcd" TO PARAM2.

       CALL 'myfun'  USING BY VALUE 0     *> pass null pointer

                         BY REFERENCE PARAM2

                         BY VALUE 4.

           STOP RUN.

           EXIT.