C#•3y ago

function pointer

I need to have some kind of array of function pointer, which can be pretty big, how to encapsulate a managed Function Pointer like a Delegate, with support of arguments by ref ?

Angius•12/16/23, 1:52 PM

You can create a delegate?

Angius•12/16/23, 1:54 PM

delegate int Foo(ref int x);

var foos = new Foo[]{
    (ref int x) => x * 2,
    (ref int x) => x * 3
};

delegate int Foo(ref int x);

var foos = new Foo[]{
    (ref int x) => x * 2,
    (ref int x) => x * 3
};

Angius•12/16/23, 1:54 PM

Something like this should work

Delta 2.1OP•12/16/23, 1:56 PM

delegate would be way to expensive for my case, I don't need any dynamic resolution, and must ensure that the function is static

Delta 2.1OP•12/16/23, 1:57 PM

I don't need an array to all function at the same time, but call a function based on ID

Angius•12/16/23, 2:05 PM

delegatedelegate is just a way to basically alias the type of a FuncFunc or ActionAction, whether you assign a lambda to it, or an existing method, is up to you

Angius•12/16/23, 2:06 PM

As long as it matches the signature

Angius•12/16/23, 2:06 PM

It's also the way to handle function pointers in C#

Angius•12/16/23, 2:06 PM

Well, Func<>Func<>, Action<>Action<> and delegatedelegate are

AAngius `delegate` is just a way to basically alias the type of a `Func` or `Action`, wh...

Delta 2.1OP•12/16/23, 2:15 PM

delegate support references on the parameter, but they are way bigger than a function pointer

Delta 2.1OP•12/16/23, 2:15 PM

(I will have something like 150k of them in memory...)

jen•12/16/23, 3:05 PM

do you know its too big, or do you think it will be too big?

Delta 2.1OP•12/16/23, 4:45 PM

I believe 24k set of at least 10 pointers is too big

333fred•12/16/23, 7:07 PM

That's something like 240K of memory. That's nothing

Delta 2.1OP•12/17/23, 7:56 PM

8 times this, because pointers use 8 bytes, and delegate use much more

333fred•12/17/23, 7:59 PM

They don't use much more

333fred•12/17/23, 8:00 PM

And that's still an extremely small amount of memory

333fred•12/17/23, 8:00 PM

Measure how much memory you actually end up using, and then decide if that's a problem

333fred•12/17/23, 8:00 PM

Don't just micro-optimize right out of the gate

MODiX•12/17/23, 8:07 PM

Angius

REPL Result: Success

unsafe {
    Console.Write(sizeof(Func<int,int>));
}

unsafe {
    Console.Write(sizeof(Func<int,int>));
}

Console Output

Quoted by

@85903769203642368 from #bot-spam (click here)

Compile: 449.975ms | Execution: 23.616ms | React with ❌ to remove this embed.

Angius•12/17/23, 8:07 PM

You're still looking at kilobytes

Angius•12/17/23, 8:07 PM

A megabyte and change, at most

Delta 2.1OP•12/18/23, 6:28 AM

I lose control over data used by the callback

333fred•12/18/23, 6:36 AM

What?

Delta 2.1OP•12/18/23, 3:32 PM

Lambda and méthods can use data other than the parameters

333fred•12/18/23, 4:21 PM

Ok?

333fred•12/18/23, 6:33 PM

You're not really explaining why this is a bad thing

333fred•12/18/23, 6:35 PM

Indeed, a delegate can have a closure. But one of the following will be true:

The delegate didn't actually have a closure, so you're paying one extra pointer's worth of space to track that nothing is there.
The delegate did need a closure, and you are either storing that extra information somewhere else, or the function pointer doesn't work

333fred•12/18/23, 6:36 PM

I would highly, highly suggest just seeing how much memory you're using, and decide at that point whether it's too much

function pointer

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