@Override
  public synchronized void reset() throws IOException {
    if (!in.markSupported()) {
      throw new IOException("Mark not supported");
    }
    if (mark == -1) {
      throw new IOException("Mark not set");
    }

    in.reset();
    count = mark;
  }
Returns the number of bytes read.
micrometer/src/main/java/feign/micrometer/CountingInputStream.java