[Mono-devel-list] Performance w/ boxing

[Piers Haken]

Yeah, just use  

	void function (ref int a) {}

You can pass references to unboxed ints, boxed ints, or fields, however you
can't pass indexers or properties.

Piers.


-----Original Message-----
From: mono-devel-list-admin at lists.ximian.com
[mailto:mono-devel-list-admin at lists.ximian.com] On Behalf Of Jaroslaw
Kowalski
Sent: Thursday, February 19, 2004 11:40 PM
To: Ben Maurer
Cc: Mono Development
Subject: Re: [Mono-devel-list] Performance w/ boxing

Thanks for your reply.

BTW. How can I use a class similar to "BoxedInt" that you've mentioned? Is
it supported with C#? DO I have to use unsafe code for this?

One more concern:

Is it possible (perhaps at the IL level) to specify an argument type of
"boxed int32" or something similar?

I want a function to be passed either an integer or NULL. I don't want to
allow the string to be passed there and if I declare the formal parameter as
"object" I have no control over what can be passed there.

Conceptually it would be something like:

void function(boxed int a)
{
    if (a == null)
    {
    }
    else
    {
        int k = (int)a;
    }
}

function(3);       // works
function(null);    // works
function("aaa");   // fails

Jarek
----- Original Message -----
From: "Ben Maurer" <bmaurer at users.sourceforge.net>
To: "Jaroslaw Kowalski" <jaak at zd.com.pl>
Cc: "Mono Development" <mono-devel-list at lists.ximian.com>
Sent: Friday, February 20, 2004 1:57 AM
Subject: Re: [Mono-devel-list] Performance w/ boxing


> On Thu, 2004-02-19 at 18:07, Jaroslaw Kowalski wrote:
> > Is it possible to share the boxed objects in case when they hold the
same
> > value? Considering the following statements:
> >
> > object o1 = 2;
> > object o2 = 2;
> >
> > Is it possible to have o1 and o2 refer to the same object on heap? What
> > about lock() on such objects?
>
> Not at all. According to the CLI spec:
>
> 'Unlike box, which is required to make a copy of a value type for use in
> the object, unbox is not required to copy the value type from the
> object. Typically it simply computes the address of the value type that
> is already present inside of the boxed object.'
>
> In short, you basically get back a pointer to the value. A consequence
> of this is that you can modify the value inside the box.
>
> So, in pseudo code, this:
>
> object o = 2;
> object b = o;
> ((BoxedInt) o).IntValue = 3;
> Console.WriteLine ("O: {0}; B: {1}", o, b);
>
> will print
>
> O: 3; B: 3
>
> So, lets say, with your idea, we did:
> object o = 2;
> object b = 2;
> ((BoxedInt) o).IntValue = 3;
> Console.WriteLine ("O: {0}; B: {1}", o, b);
>
> It would print the same as above. This is not correct.
>
> Also, even if it were correct, there are threading issues, etc.
>
> -- Ben
>

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