convertBits function

List<int> convertBits(List<int> data, int fromBits, int toBits, bool pad,)

Implementation

List<int> convertBits(List<int> data, int fromBits, int toBits, bool pad) {
  var acc = 0;
  var bits = 0;
  final maxv = (1 << toBits) - 1;
  final result = <int>[];

  for (final value in data) {
    if (value < 0 || value >> fromBits != 0) {
      throw Exception('Invalid value: $value');
    }
    acc = (acc << fromBits) | value;
    bits += fromBits;

    while (bits >= toBits) {
      bits -= toBits;
      result.add((acc >> bits) & maxv);
    }
  }

  if (pad) {
    if (bits > 0) {
      result.add((acc << (toBits - bits)) & maxv);
    }
  } else if (bits >= fromBits || ((acc << (toBits - bits)) & maxv) != 0) {
    throw Exception('Invalid data');
  }

  return result;
}