def IO.FS.Stream.readUTF8 (h : Stream) (nBytes : Nat) : IO String

def IO.FS.Stream.readJson (h : Stream) (nBytes : Nat) : IO Lean.Json

Consumes nBytes bytes from the stream, interprets the bytes as a utf-8 string and the string as a valid JSON object.

def IO.FS.Stream.writeJson (h : Stream) (j : Lean.Json) : IO Unit