Convert or verify the ethereum address into checksum address in dart/flutter

checkSum_of_ethAddress.dart

import 'dart:typed_data';
import 'package:convert/convert.dart';
import 'package:pointycastle/digests/keccak.dart';

/// This gist/function helps in convertion or verification of the ethereum address
/// Why checksum is explained here: https://coincodex.com/article/2078/ethereum-address-checksum-explained/
String toChecksum(String ethAddress) {
  // Checking for 0x prefix
  String addrWithoutChecksum = ethAddress.substring(0, 2) == '0x'
      ? ethAddress.substring(2, ethAddress.length)
      : ethAddress;

  /// Address should be size 20 bytes ie., 40 hex characters
  if (addrWithoutChecksum.length != 40) {
    throw "invalid ethereum address length";
  }

  addrWithoutChecksum = addrWithoutChecksum.toLowerCase();
  // Hash the address
  final List<int> codeUnits = addrWithoutChecksum.codeUnits;
  final Uint8List unit8List = Uint8List.fromList(codeUnits);
  final KeccakDigest keccakDigest = KeccakDigest(256);
  Uint8List hashedAddr = keccakDigest.process(unit8List);
  String hashedAddrInString = hex.encode(hashedAddr);

  // Generation of checksum
  String addrWithChecksum = "0x";
  for (int j = 0; j < addrWithoutChecksum.length; j++) {
    final int i = int.parse(hashedAddrInString[j], radix: 16);
    if (i > 7) {
      addrWithChecksum += addrWithoutChecksum[j].toUpperCase();
    } else {
      addrWithChecksum += addrWithoutChecksum[j];
    }
  }
  return addrWithChecksum;
}