fromBytes static method

int fromBytes(List<int> bytes, { Endian byteOrder = Endian.big, bool sign = false, })

Converts a list of bytes to an integer, following the given byte order. Uses native int math when safe; otherwise decodes via BigInt and checks isValidInt before converting back, throwing instead of silently losing precision.

Implementation

static int fromBytes(
  List<int> bytes, {
  Endian byteOrder = Endian.big,
  bool sign = false,
}) {
  if (bytes.isEmpty) return 0;

  if (bytes.length > 6) {
    final big = BigintUtils.fromBytes(
      bytes,
      byteOrder: byteOrder,
      sign: sign,
    );
    if (big.isValidInt) return big.toInt();
    throw ArgumentException.invalidOperationArguments(
      'fromBytes',
      name: 'bytes',
      reason: 'Value too large to fit in a Dart int.',
    );
  }

  final ordered =
      byteOrder == Endian.little ? bytes.reversed.toList() : bytes;

  int result;
  if (ordered.length > 4) {
    final int upperPart = _fromBytesUpTo4(
      ordered.sublist(0, ordered.length - 4),
    );
    final int lowerPart = _fromBytesUpTo4(
      ordered.sublist(ordered.length - 4),
    );
    result = upperPart * 0x100000000 + lowerPart; // avoid << 32
  } else {
    result = _fromBytesUpTo4(ordered);
  }

  if (sign && (ordered[0] & 0x80) != 0) {
    result -= 1 << (ordered.length * 8); // safe: length*8 <= 48 bits here
  }

  return result;
}