tryParse static method

PgDecimal? tryParse(String source)

Como PgDecimal.parse, mas devolve null se o texto não for um número.

Implementation

static PgDecimal? tryParse(String source) {
  final text = source.trim();
  if (text.isEmpty) return null;
  final lower = text.toLowerCase();
  switch (lower) {
    case 'nan':
      return nan;
    case 'infinity':
    case '+infinity':
    case 'inf':
    case '+inf':
      return infinity;
    case '-infinity':
    case '-inf':
      return negativeInfinity;
  }

  var i = 0;
  var negative = false;
  final first = text.codeUnitAt(0);
  if (first == 0x2B || first == 0x2D) {
    negative = first == 0x2D;
    i++;
  }
  final digits = StringBuffer();
  var fractionDigits = 0;
  var seenPoint = false;
  var anyDigit = false;
  for (; i < text.length; i++) {
    final c = text.codeUnitAt(i);
    if (c >= 0x30 && c <= 0x39) {
      digits.writeCharCode(c);
      anyDigit = true;
      if (seenPoint) fractionDigits++;
    } else if (c == 0x2E && !seenPoint) {
      seenPoint = true;
    } else {
      break;
    }
  }
  if (!anyDigit) return null;

  var exponent = 0;
  if (i < text.length) {
    final c = text.codeUnitAt(i);
    if (c != 0x65 && c != 0x45) return null; // e / E
    i++;
    var expNegative = false;
    if (i < text.length) {
      final s = text.codeUnitAt(i);
      if (s == 0x2B || s == 0x2D) {
        expNegative = s == 0x2D;
        i++;
      }
    }
    final start = i;
    for (; i < text.length; i++) {
      final c = text.codeUnitAt(i);
      if (c < 0x30 || c > 0x39) return null;
    }
    if (i == start || i - start > 9) return null;
    exponent = int.parse(text.substring(start, i));
    if (exponent > 1000000) return null;
    if (expNegative) exponent = -exponent;
  }

  var unscaled = BigInt.parse(digits.toString());
  if (negative) unscaled = -unscaled;
  // Escala como no PostgreSQL: dígitos depois do ponto menos o expoente.
  final scale = fractionDigits - exponent;
  if (scale >= 0) return PgDecimal._finiteValue(unscaled, scale);
  return PgDecimal._finiteValue(unscaled * _pow10(-scale), 0);
}