I did write one, but I needed to because the already-written data must be recoverable on a crash (to be able to recover partially written files) since this is in a crash reporter - and also the encoder needs to be async-safe.

https://github.com/kstenerud/KSCrash/blob/master/Sources/KSC...

And yeah, writing a JSON codec sucks.

So I'm in the process of replacing it with a BONJSON codec, which has the same capabilities, is still async-safe and crash resilient, and is 35x faster with less code.

https://github.com/kstenerud/ksbonjson/blob/main/library/src...

https://github.com/kstenerud/ksbonjson/blob/main/library/src...