encode method

@override List<int> encode(String value)

Encode the provided value as a Compact Uint (CUint) in Substrate SCALE format.

Implementation

@override
List<int> encode(String value) {
  final v = BigInt.tryParse(value);

  if (v != null) {
    /// The maximum value for a single-byte encoding mode (6 bits).
    final BigInt singleByteModeMaxVal = (BigInt.one << 6) - BigInt.one;

    if (v <= singleByteModeMaxVal) {
      return (v << 2).toLeBytes(length: 1);
    }

    /// The maximum value for a two-byte encoding mode (14 bits).
    final BigInt twoByteModeMaxVal = (BigInt.one << 14) - BigInt.one;
    if (v <= twoByteModeMaxVal) {
      return ((v << 2) | BigInt.from(0x01)).toLeBytes(length: 2);
    }

    /// The maximum value for a four-byte encoding mode (30 bits).
    final BigInt fourByteModeMaxVal = (BigInt.one << 30) - BigInt.one;
    if (v <= fourByteModeMaxVal) {
      return ((v << 2) | BigInt.from(0x02)).toLeBytes(length: 4);
    }

    /// The maximum value for the big integer encoding mode (536 bits).
    final BigInt bigIntegerModeMaxVal = (BigInt.one << 536) - BigInt.one;
    if (v <= bigIntegerModeMaxVal) {
      final List<int> valueBytes = v.toLeBytes();
      final List<int> lenBytes = ((valueBytes.length - 4 << 2) | 0x03)
          .toBytes(length: 1, byteOrder: Endian.little);
      return [...lenBytes, ...valueBytes];
    }
  }
  throw ArgumentException.invalidOperationArguments(
    "encode",
    name: "value",
    reason:
        v == null
            ? "Invalid integer for scale encoding."
            : "Value is to large for scale encoding.",
  );
}