convert method

@override List<int> convert(covariant List<int> input)

Converts input array of numbers with bit-length of source to an array of numbers with bit-length of target. The input array will be treated as a sequence of bits to convert.

After consuming all of input sequence, if there are some non-zero partial word remains, 0 will be padded on the right to make the final word.

Implementation

@override
List<int> convert(covariant List<int> input) {
  int x, p, s, t, l, n, sb, tb;
  sb = source;
  tb = target;
  if (sb < 2 || sb > 64) {
    throw ArgumentError('The source bit length should be between 2 to 64');
  }
  if (tb < 2 || tb > 64) {
    throw ArgumentError('The target bit length should be between 2 to 64');
  }

  l = input.length * sb;
  n = l ~/ tb;
  if (n * tb < l) n++;
  var out = Uint8List(n);

  // generate words from the input bits
  p = n = l = t = 0;
  s = 1 << (sb - 1);
  s = s ^ (s - 1);
  for (x in input) {
    p = (p << sb) ^ (x & s);
    t = (t << sb) ^ s;
    n += sb;
    while (n >= tb) {
      n -= tb;
      out[l++] = p >>> n;
      t >>>= tb;
      p &= t;
    }
  }

  // n > 0 means that there is a partial word remaining.
  if (n > 0) {
    // pad the word with 0 on the right to make the final word
    out[l++] = p << (tb - n);
  }

  return out;
}