Guid.parse constructor

Guid.parse(String guid)

Creates a new GUID from a string.

The string must be of the form {dddddddd-dddd-dddd-dddd-dddddddddddd}. where d is a hex digit.

Implementation

factory Guid.parse(String guid) {
  // This is a debug assert, becuase it's probably computationally expensive,
  // and int.parse will throw a FormatException anyway if it can't parse the
  // values.
  assert(RegExp(r'\{[0-9A-Fa-f]{8}(?:-[0-9A-Fa-f]{4}){3}-[0-9A-Fa-f]{12}}')
      .hasMatch(guid));

  if (guid.length != 38) {
    throw FormatException('GUID is not the correct length', guid);
  }

  // Note that the order of bytes in the returned byte array is different from
  // the string representation of a GUID value. The order of the beginning
  // four-byte group and the next two two-byte groups are reversed; the order
  // of the final two-byte group and the closing six-byte group are the same.
  //
  // The following zero-indexed list provides the offset for each 8-bit hex
  // value in the string representation.
  const offsets = [
    7, 5, 3, 1, 12, 10, 17, 15, //
    20, 22, 25, 27, 29, 31, 33, 35
  ];

  final guidAsBytes = offsets
      .map((idx) => int.parse(guid.substring(idx, idx + 2), radix: 16))
      .toList(growable: false);

  return Guid(UnmodifiableUint8ListView(Uint8List.fromList(guidAsBytes)));
}