[REBOL] Re: Problems with accessing external lib in /Command

[CRS - Psy Sel/SPO, COUSSEMENT Christophe, CPN]

Jeff:

Wow, this was a tricky one ! I tried your solution and it's OK.
Thanks you so much for helping me: I wouldn't have found it by myself ...
I will now try my new knowledge on other external libs.

Take care,

==christophe


>   Howdy, Coussement:
> 
>   Always base your routines off the C version of these
>   functions, rather than the Visual Basic function that the
>   above describes.  The addressing mode of the different
>   parameters isn't immediately clear when looking at the VB
>   declaration. 
> 
>   So we open MSVC and find:
> 
> BOOL GetUserName( 
>     LPTSTR lpBuffer,  // address of name buffer 
>     LPDWORD nSize     // address of size of name buffer 
> ); 
> 
> (ie, to decode the "Hungarian notation" above: long pointer to
> string == char* and long pointer to DWORD == int* )
> 
> Okay, now this is probably one of the most important tricks
> with REBOL/Command which is undocumented, though if you're a C
> programmer, it should be fairly intuitive.   This really needs
> to be published into an addendum, probably, so here it goes:
> 
> In C, a pointer to a struct is a pointer to the struct's first
> element.  In REBOL/Commands, all structs are passed by
> reference.  What's this mean?  This means struct! values in
> REBOL/Command allow you to make references to values, for
> example, we need this int*.  REBOL/Command doesn't directly
> provide support for pointer to int, but it's easy to make it
> using a struct! value to wrap our integer, for example:
> 
> advapi32: load/library %advapi32.dll
> 
> get-user-name: make routine! [
>     name [string!]
>     l-ref [struct! [len [integer!]]]
>     return: [integer!]
> ] advapi32 "GetUserNameA"
> 
> insert/dup name: copy "" " " 255 ;-pad the buffer
> l-ref: make struct! [len [integer!]] [255]
> get-user-name name l-ref
> trim name
> == "jeff"
> 
> 
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