let decompress input =
  let reader = Reader.of_bytes input in
  let out = Buffer.create 4096 in
  let window = Window.create () in
  let rec loop () =
    if Reader.available_bits reader <= 0 then () else
    let flag = Reader.read_bits reader 1 in
    if flag = 1 then (
      if Reader.available_bits reader < 8 then invalid_arg "decompress: truncated literal";
      let byte = Reader.read_bits reader 8 in
      Buffer.add_char out (Char.chr byte);
      Window.add_byte window byte;
      loop ()
    ) else (
      if Reader.available_bits reader < 23 then invalid_arg "decompress: truncated match";
      let distance = Reader.read_bits reader 15 in
      let length = Reader.read_bits reader 8 in
      if distance <= 0 || distance > Window.window_size then invalid_arg "decompress: invalid distance";
      for _ = 1 to length do
        let b = Window.get_byte_at_distance window distance in
        Buffer.add_char out (Char.chr b);
        Window.add_byte window b
      done;
      loop ()
    )
  in
  loop ();
  Bytes.of_string (Buffer.contents out)