numToString128 function

String numToString128(int value)

Encode a number into a string

Implementation

String numToString128(int value) {
  /// ascii code:
  /// 32: space /// 33: !  (first character except space)
  /// 48: 0
  /// 65: A  /// 90: Z
  /// 97: a  /// 122
  // const int charBase = 33;
  //'0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!"#%&()*+,-./:;<=>?@[\\]^_`{|}~€‚ƒ„…†‡ˆ‰Š‹ŒŽ‘’“”•–—˜™š›œžŸ¡¢£¤¥¦§¨©ª«¬®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ';
  const charBase =
      '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!"#%&()*+,-./:;<=>?@[]^_`{|}~€‚ƒ„…†‡•–™¢£¤¥©®±µ¶º»¼½¾ÀÆÇÈÌÐÑÒ×ØÙÝÞßæç';
  assert(charBase.length >= 128, 'numToString128 const charBase length < 128');

  if (value == 0) {
    return '#0';
  }

  var res = '#';

  assert(value >= 0, 'numToString should provide positive value.');
  // if (value < 0) {
  //   value = -value;
  //   res += '-';
  // }

  final list = <String>[];
  while (value > 0) {
    /// 64 group
    // final remainder = value & 63;
    // value = value >> 6; // == divide by 64

    /// 128 group
    final remainder = value & 127;
    value = value >> 7; // == divide by 128
    /// num to char, base on charBase
    //final char = String.fromCharCode(remainder + charBase);
    final char = charBase[remainder];
    list.add(char);
  }

  for (var i = list.length - 1; i >= 0; i--) {
    res += list[i];
  }

  return res;
}