Converts a bitstring into a number

gistfile1.hrl

-spec(bitstring_to_number/1::(BitString::bitstring()) -> number()).
bitstring_to_number(BitString) ->
  bitstring_to_number(BitString, bit_size(BitString), 0).

bitstring_to_number(_BitString, 0, Acc) -> Acc;
bitstring_to_number(BitString, CurrBitNum, Acc) ->
  BitsToSkip = bit_size(BitString) - CurrBitNum,
  <<_:BitsToSkip/bitstring, CurrentBit:1/bitstring, _/bitstring>> = BitString,
  Addition = case CurrentBit of
    <<1:1>> -> 1 bsl (CurrBitNum - 1);
    _ -> 0
  end,
  bitstring_to_number(BitString, CurrBitNum - 1, Acc + Addition).