Is using __makeref safe if I just plan to build for Windows and Mac?

It is undocumented and has portability issues. I got it here. I wanted to use it for serialization using reflection. Didn't think it would be hard when dealing with value types.

I would just use boxing if __makeref is just trouble. I've read that it's fast.

 

If you want speed use UnsafeUtility.GetFieldOffset() and set the field value directly

 

How do you exactly set the value? I assume that you convert the struct into a byte array then write the bytes to the index returned by UnsafeUtility.GetFieldOffset().

 

I think you're supposed to use an unsafe context, get a pointer to the struct and then use the offset to get a pointer to your field.

 

You you should pin the object, get it's address add the offset and read/write to it. I f you want to see how to pin managed objects/arrays check https://github.com/ddalacu/USerializer

Code (CSharp):

1.  var pinnable = Unsafe.As<object, PinnableObject>(ref obj);
2.          
3. fixed (byte* objectAddress = &pinnable.Pinnable)
4. {
5.  var fieldData = objectAddress+offset;//take offset from unsafeuttility
6.  *(int*) fieldData = 112;
7.  }

 

Thanks!

 

Sorry for being dumb. I don't see the implementation of Unsafe in USerializer. Where should I get it?

Edit: So it's supposed to be in System.Runtime.CompilerServices but Unity is unable to see it.

 

I got it now after looking at other methods in UnsafeUtility:

Code (CSharp):

1. private struct Data {
2.     public float floatValue;
3.     public int intValue;
4.     public bool boolValue;
5. }
6.  
7. [Test]
8. public unsafe void SetValueUsingUnsafeUtility() {
9.     Type type = typeof(Data);
10.     FieldInfo intField = type.GetField("intValue");
11.     int fieldOffset = UnsafeUtility.GetFieldOffset(intField);
12.    
13.     Data data = new Data();
14.     void* address = UnsafeUtility.AddressOf(ref data);
15.     byte* addressAsByte = (byte*) address;
16.     byte* intFieldAddress = addressAsByte + fieldOffset;
17.     *(int*) intFieldAddress = 1;
18.    
19.     Debug.Log($"intValue: {data.intValue}");
20.     Assert.IsTrue(data.intValue == 1);
21. }

 

If you still want to get System.Runtime.CompilerServices.Unsafe in unity you can add the scoped registry found at https://github.com/xoofx/UnityNuGet and then use package manager to add it.

 

I've always used the UnsafeUtility.PinGCObjectAndGetAddress API to get a pointer to a managed objects. You also get a handle that you then need to release using UnsafeUtility.ReleaseGCObject. Pretty sure that's the easiest way to do it, it's relatively fast* and it seems pretty reliable. It is used by ECS in a couple of places.



There's also the analogical PinGCObjectAndGetAddress and PinGCArrayAndGetDataAddress APIs.

* Unity added a null check there around 2018.3 which probably slows things down. Would a throw helper method be preferable here? @Unity

 

I think the fixed way is a bit faster in il2cpp because it only calls "get_address_of_" and with UnsafeUtillity you get the method calls associated with PinGCObjectAndGetAddress/ReleaseGCObject (but be aware that fixed method skipps the object header and UnsafeUtillity does not).
I also have a question for unity, why do they use "PinGCObjectAndGetAddress/ReleaseGCObject" instead of "
void* objectAddress;
UnsafeUtility.CopyObjectAddressToPtr(target, &objectAddress);" if unity's boehm gc does not move objects in memory anyway?