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

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

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

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