Data.Codec

Tired of writing complementary parseJSON/toJSON, peek/poke or Binary get/put functions?

codec provides easy bidirectional serialization of plain Haskell records in any Applicative context. All you need to do is provide a de/serializer for every record field in any order you like, and you get a de/serializer for the whole structure. The type system ensures that you provide every record exactly once. It also includes a library for general record construction in an Applicative context, of which creating codecs is just one application.

JSON!

userCodec :: JSONCodec User
userCodec = obj "user object" $
User
  $>> f_username      >-< "user"
  >>> f_userEmail     >-< "email"
  >>> f_userLanguages >-< "languages"
  >>> f_userReferrer  >-< opt "referrer"

instance FromJSON User where
  parseJSON = parseVal userCodec

instance ToJSON User where
  toJSON = produceVal userCodec

Bit fields!

ipv4Codec :: BinaryCodec IPv4
ipv4Codec = toBytes $
  IPv4
    $>> f_version         >-< word8 4
    >>> f_ihl             >-< word8 4
    >>> f_dscp            >-< word8 6
    >>> f_ecn             >-< word8 2
    >>> f_totalLength     >-< word16be 16
    >>> f_identification  >-< word16be 16
    >>> f_flags           >-< word8 3
    >>> f_fragmentOffset  >-< word16be 13
    >>> f_timeToLive      >-< word8 8
    >>> f_protocol        >-< word8 8
    >>> f_headerChecksum  >-< word16be 16
    >>> f_sourceIP        >-< word32be 32
    >>> f_destIP          >-< word32be 32

instance Binary IPv4 where
  get = parse ipv4Codec
  put = produce ipv4Codec

Storable!

timeSpecCodec :: ForeignCodec TimeSpec
timeSpecCodec =
  TimeSpec
    $>> f_seconds     >-< field (#offset struct timespec, tv_sec)  cInt
    >>> f_nanoseconds >-< field (#offset struct timespec, tv_nsec) cInt

instance Storable TimeSpec where
  peek = peekWith timeSpecCodec
  poke = pokeWith timeSpecCodec
  ...

All of these examples use the same types and logic for constructing Codecs, and it's very easy to create Codecs for any parsing/serialization library.

See Data.Codec for an introduction.