fromBytes static method

Uint64 fromBytes(List<int> bytes, { int offset = 0, Endian endian = Endian.big, })

Parses an 8-byte unsigned integer directly into hi/lo limbs without using BigInt.

Reads 8 bytes starting at offset from bytes. Accepts any List<int> (e.g. Uint8List, List<int>, etc.).

Throws ArgumentException if there are fewer than 8 bytes available starting at offset.

Implementation

static Uint64 fromBytes(
  List<int> bytes, {
  int offset = 0,
  Endian endian = Endian.big,
}) {
  if (offset < 0 || bytes.length - offset < 8) {
    throw ArgumentException.invalidOperationArguments(
      "Uint64.fromBytes",
      reason: 'Need at least 8 bytes from offset.',
      details: {
        "offset": offset.toString(),
        "length": bytes.length.toString(),
      },
    );
  }

  int hi, lo;
  if (endian == Endian.big) {
    hi =
        (bytes[offset] << 24) |
        (bytes[offset + 1] << 16) |
        (bytes[offset + 2] << 8) |
        bytes[offset + 3];
    lo =
        (bytes[offset + 4] << 24) |
        (bytes[offset + 5] << 16) |
        (bytes[offset + 6] << 8) |
        bytes[offset + 7];
  } else {
    lo =
        (bytes[offset + 3] << 24) |
        (bytes[offset + 2] << 16) |
        (bytes[offset + 1] << 8) |
        bytes[offset];
    hi =
        (bytes[offset + 7] << 24) |
        (bytes[offset + 6] << 16) |
        (bytes[offset + 5] << 8) |
        bytes[offset + 4];
  }

  return Uint64._(hi & _mask32, lo & _mask32);
}