Function combinePrefixPatterns

docs/js/google-code-prettify.js:240–471

* Given a group of RegExps, returns a RegExp that globally * matches the union of the sets of strings matched by the input RegExp. * Since it matches globally, if the input strings have a start-of-input * anchor (/^.../), it is ignored for the purposes of unioning. * @par

(regexs)

   * @return {RegExp} a global regex.
   */
  function combinePrefixPatterns(regexs) {
    var capturedGroupIndex = 0;
  
    var needToFoldCase = false;
    var ignoreCase = false;
    for (var i = 0, n = regexs.length; i < n; ++i) {
      var regex = regexs[i];
      if (regex.ignoreCase) {
        ignoreCase = true;
      } else if (/[a-z]/i.test(regex.source.replace(
                     /\\u[0-9a-f]{4}|\\x[0-9a-f]{2}|\\[^ux]/gi, ''))) {
        needToFoldCase = true;
        ignoreCase = false;
        break;
      }
    }
  
    var escapeCharToCodeUnit = {
      'b': 8,
      't': 9,
      'n': 0xa,
      'v': 0xb,
      'f': 0xc,
      'r': 0xd
    };
  
    function decodeEscape(charsetPart) {
      var cc0 = charsetPart.charCodeAt(0);
      if (cc0 !== 92 /* \\ */) {
        return cc0;
      }
      var c1 = charsetPart.charAt(1);
      cc0 = escapeCharToCodeUnit[c1];
      if (cc0) {
        return cc0;
      } else if ('0' <= c1 && c1 <= '7') {
        return parseInt(charsetPart.substring(1), 8);
      } else if (c1 === 'u' || c1 === 'x') {
        return parseInt(charsetPart.substring(2), 16);
      } else {
        return charsetPart.charCodeAt(1);
      }
    }
  
    function encodeEscape(charCode) {
      if (charCode < 0x20) {
        return (charCode < 0x10 ? '\\x0' : '\\x') + charCode.toString(16);
      }
      var ch = String.fromCharCode(charCode);
      return (ch === '\\' || ch === '-' || ch === ']' || ch === '^')
          ? "\\" + ch : ch;
    }
  
    function caseFoldCharset(charSet) {
      var charsetParts = charSet.substring(1, charSet.length - 1).match(
          new RegExp(
              '\\\\u[0-9A-Fa-f]{4}'
              + '|\\\\x[0-9A-Fa-f]{2}'