Q39361: Sample Program; BASIC Invoking C Function That Returns String

Article: Q39361
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom SR# S881207-17 | mspl13_basic
Last Modified: 1-FEB-1990

The sample program below demonstrates a BASIC program calling a C
routine that returns a BASIC string descriptor. This programming
example is a variation of the sample program located on Page 310 of
the "Microsoft QuickBASIC 4.0: Learning and Using" manual.

This information applies to Microsoft QuickBASIC Versions 4.00, 4.00b,
and 4.50, to Microsoft BASIC Compiler Versions 6.00 and 6.00b for
MS-DOS and MS OS/2, and to Microsoft BASIC Professional Development
System (PDS) Version 7.00 for MS-DOS and MS OS/2.

Note: The Microsoft C medium-memory model should be used to ensure
that the C string is in DGROUP.

Note: This information does not apply if using far string support in
BASIC PDS Version 7.00 or when running inside the QuickBASIC extended
(QBX.EXE) environment with BASIC PDS Version 7.00. For information on
programming with mixed-languages using far strings refer to Chapter
13, "Mixed-Language Programming with Far Strings," in the "Microsoft
BASIC 7.0: Programmer's Guide."

The COMPILE and LINK instructions are as follows:

   BC test.bas;
   CL /AM /c tc.c
   LINK test tc /noe;

The BASIC routine is as follows:

   DECLARE FUNCTION t1$()
   a$ = t1$
   PRINT a$

The C function is as follows:

   struct bas_str{
           int sd_len;
           char *sd_addr;
           };
   char cstr[]="ABC";
   struct bas_str pascal t1()
   {
      struct bas_str str_des;
      str_des.sd_addr = cstr;
      str_des.sd_len = strlen(cstr);
      return (str_des);
   }

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