Haskell: "Reading" ByteString

Question

How do I convert a ByteString representation of an Integer to ... well Integer? Is there a special read function for ByteStrings or do I have to unpack first than use normal read?

Thanks.

Answer 1

You can use readInt or readInteger from Data.ByteString.Char8. If you want to read some other type of data, you'll need to write your own parser; the best choice is probably attoparsec, which is a library for writing fast ByteString and Text parsers, similar to Parsec.

Answer 2

In addition to ehird's excellent suggestions, you can also use Data.Binary.Get for reading fixed-length integers.

ghci> :m +Data.Binary.Get
ghci> :t runGet getWord64le
ByteString -> Word64