Path: news.cs.au.dk!Morten.Grouleff.Mjolner.Informatics
From: Morten Grouleff <mg@mjolner.dk>
Newsgroups: comp.lang.beta
Subject: Re: MB_YESNOCANCEL, MB_YESNO, MB_RETRYCANCEL ...
Date: 01 Mar 1999 13:18:37 +0100
Organization: Mjolner Informatics.
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"Sascha Kimmel" <kimmel@tricos.com> writes:

[...]

> And could someone please explain how to implement certain WINAPI functions
> like the following one in BETA?
> 
> BOOL GetUserName(
>   LPTSTR lpBuffer,  // address of name buffer
>   LPDWORD nSize     // address of size of name buffer
> );

win32lib/winbase.bet:

(* BOOL WINAPI GetUserNameA (LPSTR lpBuffer,LPDWORD nSize ); *)
GetUserName: external
  (# name: @integer;
     length: @integer;
     result: @boolean;
  enter (name, length)
  do 'GetUserNameA' -> callStd;
  exit result
  #);

> My problem is that I don't know how to get the address of a variable.
> Adresses and addresses.. well, yes, it's C :)

You really should not get the address of an attribbute of a BETA object,
as it may be changes by the garbage collector.

But there are other ways...:

ORIGIN '~beta/basiclib/betaenv';
INCLUDE '~beta/sysutils/cstring';
INCLUDE '~beta/win32lib/winbase';
--PROGRAM: descriptor--
(# cs: @CString;
   lgt, result: @Integer;
do 256->lgt;
   lgt->cs.init;
   (cs, @@lgt)->GetUserName->result;
   (if result<>0 then
       cs.get->screen.putLine;
   if);
   cs.free;
#)

Here, CString is used to store the string.  @@lgt is the address of the
integer lgt.  Note that this code is safe, but only because the address
is only used in a call of an external function.  Using @@lgt in any
other way leads to unpredictable errors.  This is not a supported part
of the implementation and may change without notice.

Regards,
-- 
**  Morten Grouleff:     <URL: http://www.grouleff.dk/>          **
**  Earthworm Jim PC:    <URL: http://www.grouleff.dk/ewj.html>  **
**  Mjølner Informatics: <URL: http://www.mjolner.com>           **