function indexBig5PointerFor(code_point) {

    // 1. Let index be index big5.
    var index_ = index('big5');

    // 2. If code point is U+2550, U+255E, U+2561, U+256A, U+5341, or
    // U+5345, return the last pointer corresponding to code point in
    // index.
    if (code_point === 0x2550 || code_point === 0x255E ||
        code_point === 0x2561 || code_point === 0x256A ||
        code_point === 0x5341 || code_point === 0x5345) {
      return index.lastIndexOf(code_point);
    }

    // 3. Return the index pointer for code point in index.
    return indexPointerFor(code_point, index_);
  }
@param {number} code_point The |code_point| to search for in the big5 index.
@return {?number} The code point corresponding to |pointer| in |index|,
    or null if |code point| is not in the big5 index.