def pack_urlsafe_base64digest(bin)
      str = pack_base64digest(bin)
      str.tr!('+/'.freeze, '-_'.freeze)
      str.tr!('='.freeze, ''.freeze)
      str
    end
def pack_urlsafe_base64digest(bin)
      str = pack_base64digest(bin)
      str.tr!('+/'.freeze, '-_'.freeze)
      str.tr!('='.freeze, ''.freeze)
      str
    end
Internal: Pack a binary digest to a urlsafe base64 encoded string.

 bin - String bytes

 Returns urlsafe base64 String.