bit-protocol: Encode binary protocols with some odd bit numbers into a bytestring

[ bits, bsd3, bytes, data, library, parsing, protocols ] [ Propose Tags ]

Encode binary protocols with some odd bit numbers into a bytestring.


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Versions 0.1.0.0, 0.2.0.0, 0.2.1.0, 0.2.2.0, 0.2.3.0
Dependencies base (>=4.7 && <5), base64-bytestring, bytestring, dlist, ghc-prim, QuickCheck [details]
License BSD-3-Clause
Copyright Kostiantyn Rybnikov
Author Kostiantyn Rybnikov
Maintainer k-bx@k-bx.com
Category Data, Parsing, Bits, Bytes, Protocols
Home page https://github.com/k-bx/bit-protocol#readme
Uploaded by k_bx at Mon Jul 30 16:26:53 UTC 2018
Distributions NixOS:0.2.3.0
Downloads 222 total (30 in the last 30 days)
Rating 2.0 (votes: 1) [estimated by rule of succession]
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Status Docs available [build log]
Last success reported on 2018-07-30 [all 1 reports]
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Readme for bit-protocol-0.2.3.0

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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)