Re: options(*varsize)

[Joep Beckeringh <joep@xxxxxxxxxxxxxxxxxxx>]

Indeed, if you pass a pointer and an integer, you can handle large amounts of 
memory. A varying field consists of a 2-byte integer containing the actual 
length and the character data. Gives you an opportunity to pass data and length 
in one parameter, but you are limited to 64k.

When you use an options(*varsize) field, the length in the prototype does not 
really matter, because the compiler does not check it. It might have effect if 
you use CONST as well and the compiler has to create a temporary variable. Not 
sure about that, though.

Joep Beckeringh


brian wrote:
> On Fri, 27 May 2005, Joep Beckeringh wrote:
>
>
> > is to have an extra parameter for the length (as most APIs have);
> > another way is to use a VARYING length parameter.
>
>
> If I pass a pointer and a 10u 0, my data can be 4GB in length (it's
> restricted only by the size of the length parameter). VARYING seems
> different. If I could say that my field was a 4294967296a VARYING, that'd
> be great, but I don't think I can. The D spec length field isn't wide
> enough.
>
> If I'm stuck with passing an options(*varsize) field, I don't understand
> what the length of that field should be. It doesn't seem to be a minimum
> or maximum (or anything).