I need a function which has fast conversion from Bytestring to Integer.
I am currently using this:

import qualified Data.ByteString.Lazy.Char8 as BS

readInteger :: BS.ByteString -> Integer
readInteger x =
  case BS.readInteger x of Just (i,_) -> i

Are there faster implementations? This function takes 1.8 seconds to
convert 2000 integers of length 10^13000. I need it to be smaller that
0.5 sec. Is it possible?