C#•6mo 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 ?

15 Replies

Angius•6mo ago

You can create a delegate?

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
};

Something like this should work

Delta 2.1•6mo ago

delegate would be way to expensive for my case, I don't need any dynamic resolution, and must ensure that the function is static 😅 I don't need an array to all function at the same time, but call a function based on ID

Angius•6mo ago

delegate is just a way to basically alias the type of a Func or Action, whether you assign a lambda to it, or an existing method, is up to you As long as it matches the signature It's also the way to handle function pointers in C# Well, Func<>, Action<> and delegate are

Delta 2.1•6mo ago

delegate support references on the parameter, but they are way bigger than a function pointer (I will have something like 150k of them in memory...)

alex•6mo ago

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

Delta 2.1•6mo ago

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

333fred•6mo ago

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

Delta 2.1•6mo ago

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

333fred•6mo ago

They don't use much more And that's still an extremely small amount of memory Measure how much memory you actually end up using, and then decide if that's a problem Don't just micro-optimize right out of the gate

MODiX•6mo ago

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•6mo ago

You're still looking at kilobytes A megabyte and change, at most

Delta 2.1•6mo ago

I lose control over data used by the callback 🤨

333fred•6mo ago

What?

Delta 2.1•6mo ago

Lambda and méthods can use data other than the parameters

333fred•6mo ago

Ok? You're not really explaining why this is a bad thing Indeed, a delegate can have a closure. But one of the following will be true: 1. 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. 2. The delegate did need a closure, and you are either storing that extra information somewhere else, or the function pointer doesn't work I would highly, highly suggest just seeing how much memory you're using, and decide at that point whether it's too much

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function pointer