Add support for u128

[pronebird]

Hi,

It seems that u128 is not supported out of box. I think we should fix it

[mhammond]

The challenge here is probably bindings - eg, how would Kotlin use it?

[paxbun]

Even Swift has added support for 128-bit integer types recently: https://developer.apple.com/documentation/swift/int128, so it seems the only issue is Kotlin Multiplatform here (Java has BigInteger; see below). It would be great if we could pass u128 directly; it is useful for passing UUIDs.

First-party bindgens

• Python: int
• Swift: Int128 and UInt128 in Swift 6 (iOS 18+, macOS 15+)
• Kotlin/JVM: java.math.BigInteger
• Ruby: Integer in CRuby 2.4+

Third-party bindgens

• JavaScript: BigInt
• Kotlin Multiplatform: :cry:
• Go: Int in "math/big"
• C#: System.Int128 and System.UInt128 in .NET 7+, or System.Numerics.BigInteger
• Dart: BigInt in dart:core
• Java: java.math.BigInteger

When the FFI-1.0 proposal is completed, I think we can make our own library that implements 128-bit integers.

[pronebird]

Not sure if that's the way out but if Kotlin does not support u128, then we could default to String conversion. This is what I am doing at the moment with protobuf which does not support u128 out of box.