How much memory does a reference to a reference type take up?

[Grofit]

Hey,

Kinda a weird one i know, but to keep the question simple lets say you have a class that you made, and you have a list of them. Then you need to make objects that reference that one object...

So in this scenario there is 1 reference type allocated in memory that contains some bits and bobs, then there are lets say 10000 other objects that reference the 1 allocated object, although the object is already in memory, surely the other objects have to allocate a bit of space to know what address they are pointing to...

public class AllocatedClass
{
    public int SomeVar;
}

public class ReferencerClass
{
    protected AllocatedClass AllocatedClassLookup;
    public ReferencerClass(AllocatedClass Lookup) { AllocatedClassLookup = Lookup; }
}

AllocatedClass Allocated = new AllocatedClass();
List<ReferencerClass> ReferenceList = new List<ReferencerClass>();
for(uint i =0; i<uint.Max;i++)
{ ReferenceList.Add( new ReferencerClass(Allocated) ); }

That above example is pretty much what im talking about, there would be 1 allocation of the first class and all the others would only have a reference to that variable, although its an immutable reference how much space does each one take up roughly?

[Alsvha]

If I recall correct it should usually be 4 byte on 32bit and 8 byte on a 64 bit, as it is a number pointer to a memory location.
I'm not 100% sure though.

[Grofit]

I thought it would probably be something like that as its just going to be an address lookup right?

[Alsvha]

I thought it would probably be something like that as its just going to be an address lookup right?

Yes - a reference itself should just be taking the space it needs to hold the memory address. Which is why I recall it as 4/8 depending on 32/64bit

[Mutant_Fruit]

You're actually confusing a few things here In .NET you can't store a pointer to an object, so there is no way to store a 'reference to a reference'.

Every class you instantiate has 12 bytes of associated overhead. 4 bytes for type information, 4 bytes for the sync block (so you can use the 'lock' keyword) and 4 bytes i can't remember. That's the absolute minimum size a .NET object can be.

public class ReferencerClass
{
    protected AllocatedClass AllocatedClassLookup;
    public ReferencerClass(AllocatedClass Lookup) { AllocatedClassLookup = Lookup; }
}

This would be 12 + size (void*) bytes in size, as the field is essentially storing a pointer to another object. So on a 32bit system that would make each instance of your 'Referencer' class be 16 bytes.

[Grofit]

Ah brilliant, thanks for clearing it up... when i say pointer i mean the logic of a pointer... i read the address is not a reference article previously, but its just hard to get away from C++ naming conventions...