int decodeVlq()

in lib/src/vlq.dart [66:101]

• 25 lines of code
• 6 McCabe index (conditional complexity)

int decodeVlq(Iterator<String> chars) {
  var result = 0;
  var stop = false;
  var shift = 0;
  while (!stop) {
    if (!chars.moveNext()) throw StateError('incomplete VLQ value');
    var char = chars.current;
    var digit = _digits[char];
    if (digit == null) {
      throw FormatException('invalid character in VLQ encoding: $char');
    }
    stop = (digit & vlqContinuationBit) == 0;
    digit &= vlqBaseMask;
    result += (digit << shift);
    shift += vlqBaseShift;
  }

  // Result uses the least significant bit as a sign bit. We convert it into a
  // two-complement value. For example,
  //   2 (10 binary) becomes 1
  //   3 (11 binary) becomes -1
  //   4 (100 binary) becomes 2
  //   5 (101 binary) becomes -2
  //   6 (110 binary) becomes 3
  //   7 (111 binary) becomes -3
  var negate = (result & 1) == 1;
  result = result >> 1;
  result = negate ? -result : result;

  // TODO(sigmund): can we detect this earlier?
  if (result < minInt32 || result > maxInt32) {
    throw FormatException(
        'expected an encoded 32 bit int, but we got: $result');
  }
  return result;
}