code: public static void copy(Readable from, Appendable to) throws IOException {
       CharBuffer buf = CharBuffer.allocate(2048);
       for (;;) {
         int r = from.read(buf);
         if (r == -1) break;
         buf.flip();
         to.append(buf, 0, r);
       }
    }
docs: Copies all content from {@code from} to {@code to}.