int numChars = reader.read(charBuffer.array(), limit, availableCapacity(charBuffer));
    if (numChars == -1) {
      endOfInput = true;
    } else {
      Java8Compatibility.limit(charBuffer, limit + numChars);
    }
  }

  /** Returns the number of elements between the limit and capacity. */
  private static int availableCapacity(Buffer buffer) {
    return buffer.capacity() - buffer.limit();
  }