Method toDouble

basex-core/src/main/java/org/basex/util/Token.java:544–601

Converts the specified token into a double value. @param token token to be converted @return resulting double value, or Double#NaN is returned if the input is invalid

(final byte[] token)

   * @return resulting double value, or {@link Double#NaN} is returned if the input is invalid
   */
  public static double toDouble(final byte[] token) {
    final int tl = token.length;
    int s = -1;
    while(++s < tl && ws(token[s]));
    if(s == tl) return Double.NaN;

    // check for integer value
    int e = s;
    boolean f = false;
    for(int p = s; p < tl; ++p) {
      final byte b = token[p];
      if(e == s) {
        if(digit(b) || b == '+') continue;
        if(ws(b)) {
          e = p + 1;
        } else {
          f = b == 'e' || b == 'E' || b == '.' || b == '-';
          if(!f) return Double.NaN;
        }
      } else if(!ws(b)) {
        return Double.NaN;
      }
    }
    if(e == s) e = tl;
    if(!f && e - s <= 9) {
      final int d = toInt(token, s, e);
      return d == Integer.MIN_VALUE ? Double.NaN : d;
    }

    // check if the value is a double
    final int l = e - s;
    if(l == 1) return Double.NaN;
    final char[] str = new char[l];
    int sd = 0, se = 0;
    for(int p = 0; p < l; ++p) {
      char b = (char) token[s + p];
      if(b == 'e' || b == 'E') {
        // 'e1', '1e', '1e1e1'
        b = p == 0 || p + 1 == l || ++se > 1 ? 0 : 'e';
      } else if(b == '-') {
        // '1-', '1.-1', '1-1'
        if(p > 0 && (p + 1 == l || str[p - 1] != 'e')) b = 0;
      } else if(b == '.') {
        // '1e.', '1.1.1',
        if(p > 0 && str[p - 1] == 'e' || ++sd > 1) b = 0;
      }
      if(b == 0) return Double.NaN;
      str[p] = b;
    }

    // parse as double value
    try {
      return Double.parseDouble(new String(str));
    } catch(final NumberFormatException ex) {
      Util.debug(ex);
      return Double.NaN;
    }
  }