flutter_appfx/lib/util/hexUtils.dart

import 'dart:convert' show utf8;
import 'dart:typed_data';
import 'package:convert/convert.dart' show hex;
import "package:pointycastle/digests/keccak.dart";


bool isHexPrefixed(String str) {
  ArgumentError.checkNotNull(str);

  return str.startsWith('0x');
}

/// Is the string a hex string.
bool isHexString(String value, {int length = 0}) {
  ArgumentError.checkNotNull(value);

  // if (!RegExp('^0x[0-9A-Fa-f]*\$').hasMatch(value)) return false;
  if (!RegExp(r'\b(?:0[xX])?[0-9a-fA-F]+\b').hasMatch(value)) return false;
  if (length > 0 && value.length != 2 + 2 * length) return false;

  return true;
}

String stripHexPrefix(String hexString) {
  ArgumentError.checkNotNull(hexString);

  if (hexString.startsWith("0x") || hexString.startsWith("0X")) {
    return hexString.substring(2);
  }
  return hexString;
}

String addHexPrefix(String hexString) {
  ArgumentError.checkNotNull(hexString);

  if (!hexString.startsWith("0x") && !hexString.startsWith("0X")) {
    return '0x$hexString';
  }
  return hexString;
}



/// Pads a [String] to have an even length
String padToEven(String value) {
  ArgumentError.checkNotNull(value);

  var a = '$value';
  if (a.length % 2 == 1) a = '0${a}';

  return a;
}

/// Converts a [int] into a hex [String]
String intToHex(i) {
  ArgumentError.checkNotNull(i);

  return '0x${i.toRadixString(16)}';
}

/// Converts an [int] or [BigInt] to a [Uint8List]
Uint8List intToBuffer(i) {
  return Uint8List.fromList(i == null || i == 0 || i == BigInt.zero ? [] : hex.decode(padToEven(intToHex(i).substring(2))));
}

Uint8List stringToBuffer(String i) {
  return Uint8List.fromList(i.isEmpty ? [] : hex.decode(padToEven(stripHexPrefix(i))));
}

/// Get the binary size of a string
int getBinarySize(String str) {
  ArgumentError.checkNotNull(str);

  return utf8.encode(str).length;
}

/// Returns TRUE if the first specified array contains all elements from the second one. FALSE otherwise.
bool arrayContainsArray(List superset, List subset, {bool some = false}) {
  ArgumentError.checkNotNull(superset);
  ArgumentError.checkNotNull(subset);

  if (some) return Set.from(superset).intersection(Set.from(subset)).length > 0;

  return Set.from(superset).containsAll(subset);
}

/// Should be called to get utf8 from it's hex representation
String toUtf8(String hexString) {
  ArgumentError.checkNotNull(hexString);

  List<int> bufferValue = hex.decode(padToEven(stripHexPrefix(hexString).replaceAll(RegExp('^0+|0+\$'), '')));

  return utf8.decode(bufferValue);
}

/// Should be called to get ascii from it's hex representation
String toAscii(String hexString) {
  ArgumentError.checkNotNull(hexString);

  var start = hexString.startsWith(RegExp('^0x')) ? 2 : 0;
  return String.fromCharCodes(hex.decode(hexString.substring(start)));
}

/// Should be called to get hex representation (prefixed by 0x) of utf8 string
String fromUtf8(String stringValue) {
  ArgumentError.checkNotNull(stringValue);

  var stringBuffer = utf8.encode(stringValue);

  return "0x${padToEven(hex.encode(stringBuffer)).replaceAll(RegExp('^0+|0+\$'), '')}";
}

/// Should be called to get hex representation (prefixed by 0x) of ascii string
String fromAscii(String stringValue) {
  ArgumentError.checkNotNull(stringValue);

  var hexString = '';
  for (var i = 0; i < stringValue.length; i++) {
    var code = stringValue.codeUnitAt(i);
    var n = hex.encode([code]);
    hexString += n.length < 2 ? '0${n}' : n;
  }

  return '0x$hexString';
}


Uint8List hexToBytes(String hexStr) {
  final bytes = hex.decode(stripHexPrefix(hexStr));
  if (bytes is Uint8List) return bytes;
  return Uint8List.fromList(bytes);
}

String bytesToHex(List<int> bytes,
    {bool include0x = false,
      int? forcePadLength,
      bool padToEvenLength = false}) {
  var encoded = hex.encode(bytes);

  if (forcePadLength != null) {
    assert(forcePadLength >= encoded.length);

    final padding = forcePadLength - encoded.length;
    encoded = ('0' * padding) + encoded;
  }

  if (padToEvenLength && encoded.length % 2 != 0) encoded = '0$encoded';

  return (include0x ? '0x' : '') + encoded;
}



// ------------ by myself -----------


String hex2ascii(String hexString) {
  try {
    if (isHexString(hexString)) {
      hexString = stripHexPrefix(hexString);
      List<String> splitted = [];
      for (int i = 0; i < hexString.length; i = i + 2) {
        splitted.add(hexString.substring(i, i + 2));
      }
      String ascii = List.generate(splitted.length,
              (i) => String.fromCharCode(int.parse(splitted[i], radix: 16))).join();
      return ascii;
    } else {
      return '';
    }
  } catch (error) {
    return '';
  }
}

String ascii2hex(String asciiString) {
  try {
    if (asciiString.isNotEmpty) {
      String hexStr = '';
      for (int i = 0; i < asciiString.length; ++i) {
        hexStr = hexStr + asciiString.codeUnitAt(i).toRadixString(16);
      }
      return hexStr;
    } else {
      return '';
    }
  } catch (error) {
    return '';
  }
}


String hex2dec(String hexString) {
  try {
    if (isHexString(hexString)) {
      BigInt? bgInt = BigInt.tryParse(stripHexPrefix(hexString), radix:16);
      if (bgInt != null) {
        return bgInt.toRadixString(10);
      }
    }
    // else
    return '';
  } catch (error) {
    return '';
  }
}

String dec2hex(String decString) {
  try {
    if (decString.isNotEmpty) {
      BigInt? bgInt = BigInt.tryParse(decString, radix:10);
      if (bgInt != null) {
        return addHexPrefix(bgInt.toRadixString(16));
      }
    }
    // else
    return '';
  } catch (error) {
    return '';
  }
}





/// ----- to Hash -----
/// 注意：Hash256 和 Keccak256 其实不一样，
/// 但由于最早接触 Ethereum 相关代码，其中 Hash 使用的是 Keccak256，
/// 造成App其他地方的 Hash 也都沿用了 Keccak256。
/// 历史原因，不做修改。[2023-12-15 James.Zhang]

String toHash(String anyString) {
  return toKeccak256(anyString);
}

String toKeccak256(String anyString, [int bitLength = 256]) {
  var keccak = KeccakDigest(bitLength);
  keccak.update(
    Uint8List.fromList(anyString.codeUnits),
    0,
    anyString.codeUnits.length,
  );

  var out = Uint8List(bitLength ~/ 8);
  keccak.doFinal(out, 0);

  return _uint8ListToHex(out);
}

/// Character `0`.
const int _zero = 0x30;
/// Character `a`.
const int _a = 0x61;

String _uint8ListToHex(List<int> bytes) {
  final buffer = Uint8List(bytes.length * 2);

  int bufferIndex = 0;
  for (var i = 0; i < bytes.length; i++) {
    var byte = bytes[i];

    // The bitwise arithmetic here is equivalent to `byte ~/ 16` and `byte % 16`
    // for valid byte values, but is easier for dart2js to optimize given that
    // it can't prove that [byte] will always be positive.
    buffer[bufferIndex++] = _codeUnitForDigit((byte & 0xF0) >> 4);
    buffer[bufferIndex++] = _codeUnitForDigit(byte & 0x0F);
  }

  return String.fromCharCodes(buffer);
}

/// Returns the ASCII/Unicode code unit corresponding to the hexadecimal digit
/// [digit].
int _codeUnitForDigit(int digit) =>
    digit < 10 ? digit + _zero : digit + _a - 10;