getL2TxId function

String getL2TxId(int fromIdx, int tokenId, double amount, int nonce, int fee,)

Generates the Transaction Id based on the spec TxID (33 bytes) for L2Tx is: bytes: | 1 byte | 32 bytes | SHA256( 6 bytes | 4 bytes | 2 bytes| 5 bytes | 1 byte ) content: | type | SHA256(FromIdx | TokenID | Amount | Nonce | Fee ) where type for L2Tx is '2' @param {Number} fromIdx - The account index that sends the transaction @param {Number} tokenId - The tokenId being transacted @param {Number} amount - The amount being transacted @param {Number} nonce - Nonce of the transaction @param {Number} fee - The fee of the transaction @returns {String} Transaction Id

Implementation

String getL2TxId(int fromIdx, int tokenId, double amount, int nonce, int fee) {
  final fromIdxBytes = Uint8List(8);
  final fromIdxView = ByteData.view(fromIdxBytes.buffer);
  fromIdxView.setUint64(0, fromIdx);

  final tokenIdBytes = Uint8List(8);
  final tokenIdView = ByteData.view(tokenIdBytes.buffer);
  tokenIdView.setUint64(0, tokenId);

  final amountF40 = HermezCompressedAmount.compressAmount(amount).value;
  final amountBytes = Uint8List(8);
  final amountView = ByteData.view(amountBytes.buffer);
  amountView.setUint64(0, BigInt.from(amountF40).toInt());

  final nonceBytes = Uint8List(8);
  final nonceView = ByteData.view(nonceBytes.buffer);
  nonceView.setUint64(0, nonce);

  final fromIdxHex = bytesToHex(fromIdxView.buffer.asUint8List().sublist(2, 8));
  final tokenIdHex = bytesToHex(tokenIdView.buffer.asUint8List().sublist(4, 8));
  final amountHex = bytesToHex(
      amountView.buffer.asUint8List().sublist(3, 8)); // float40: 5 bytes
  final nonceHex = bytesToHex(nonceView.buffer.asUint8List().sublist(3, 8));

  String feeHex = fee.toRadixString(16);
  if (feeHex.length == 1) {
    feeHex = '0' + feeHex;
  }

  final v = fromIdxHex + tokenIdHex + amountHex + nonceHex + feeHex;
  final h = bytesToHex(keccak256(hexToBytes(v)));

  return '0x02' + h;
}