bit-protocol

A package suitable for binary protocols defined in a manner where you have bit counts not aligned by 8.

For example, if you have a protocol for sending user profiles saying:

The value sent must be a base64url-encoded string consisting of four values:

• 6 bits representing user's age
• 7 bits for their favorite number
• 5 bits for their lucky number
• 6 bits for a random number

you could use the library as follows:

import Data.BitProtocol import Data.ByteString.Base64.URL (encode) main :: IO () main = do let age = 29 fav = 12 lucky = 13 rand = 14 -- the number in protocol should be base64url(011101_0001100_01101_001110) print $ encode $ encodeBS8 $ [BitsVal 6 age, BitsVal 7 fav, BitsVal 5 lucky, BitsVal 6 rand] -- will output "dGNO" -- which is the same as `encode (BC8.pack (map chr [0b01110100, 0b01100011, 0b01001110]))` 

Parsing can be done like this:

 let (Right bs) = decode "dGNO" let (xs, BitsVal 0 0, "") = parseBS8 [6, 7, 5, 6] bs print xs -- Will output: -- ( [BitsVal 6 29, BitsVal 7 12, BitsVal 5 13, BitsVal 6 14] -- , BitsVal 0 0 -- , "") 

Warning! Does not support negative numbers.

TODO:

• use shift operations instead of division in more places
• add a performance test
• consider adding checks upon arithmetic overflows (if you use Int in quickcheck test you'll quickly find some)