Tokenizer.Probe C# (CSharp) Method

    private bool Probe(string symbol) 
    {
      int l = symbol.Length;
      int missed = l - _read.Length;
      if (missed > 0) 
      {
        int ch = 0;
        System.Text.StringBuilder sb = new System.Text.StringBuilder(_read);
        while (missed > 0 && ch != -1) 
        {
          ch = _reader.Read();
          if (ch == -1) break;
          sb.Append((char)ch);
          missed--;
        }
        _read = sb.ToString();
      }
      if (_read.Length >= l && _read.Substring(0, l).ToLower() == symbol) 
      {
        if (_read.Length > l) 
        {
          _read = _read.Substring(l);
        } 
        else 
        { 
          _read = "";
        };
        return true;
      } 
      else 
      {
        return false;
      };
    }