Method removeLeadingString

java/com/google/re2j/Parser.java:601–638

(Regexp re, int n)

  // removeLeadingString removes the first n leading runes
  // from the beginning of re.  It returns the replacement for re.
  private Regexp removeLeadingString(Regexp re, int n) {
    if (re.op == Regexp.Op.CONCAT && re.subs.length > 0) {
      // Removing a leading string in a concatenation
      // might simplify the concatenation.
      Regexp sub = removeLeadingString(re.subs[0], n);
      re.subs[0] = sub;
      if (sub.op == Regexp.Op.EMPTY_MATCH) {
        reuse(sub);
        switch (re.subs.length) {
          case 0:
          case 1:
            // Impossible but handle.
            re.op = Regexp.Op.EMPTY_MATCH;
            re.subs = null;
            break;
          case 2:
            {
              Regexp old = re;
              re = re.subs[1];
              reuse(old);
              break;
            }
          default:
            re.subs = subarray(re.subs, 1, re.subs.length);
            break;
        }
      }
      return re;
    }

    if (re.op == Regexp.Op.LITERAL) {
      re.runes = Utils.subarray(re.runes, n, re.runes.length);
      if (re.runes.length == 0) {
        re.op = Regexp.Op.EMPTY_MATCH;
      }
    }
    return re;
  }

  // leadingRegexp returns the leading regexp that re begins with.
  // The regexp refers to storage in re or its children.