Util.hs

module Network.RPCA.Util where

import Control.Concurrent.STM
import Data.Word
import Data.Bits
import qualified Data.Sequence as Seq

-- | These are the errors which can occur. You'll find the code in the
--   reply_code member of the Rpcreply
data ErrorCode = ErrNone  -- ^ no error occured
               | ErrServiceUnknown  -- ^ the service was unknown at the remote end
               | ErrMethodUnknown  -- ^ the method was unknown at the remote end
               | ErrTransportFailed  -- ^ the connection died
               | ErrTimeout  -- ^ the request timed out
               | ErrPayloadParseFailed  -- ^ remote end failed to deserialise the payload
               | ErrReplyPayloadParseFailed  -- ^ local parsing of the reply failed
               deriving (Enum, Eq, Show)

-- | Atomically update a value by applying a function to it and return
--   the old value
updateTVar :: (a -> a)  -- ^ function to apply
           -> TVar a  -- ^ value to update
           -> STM a
updateTVar f var = do
  old <- readTVar var
  writeTVar var $ f old
  return old

-- | This assumes a little endian system because I can't find a nice way to probe
--   the endianness
htons :: Word16 -> Word16
htons x = ((x .&. 255) `shiftL` 8) .|. (x `shiftR` 8)

seqToList :: Seq.Seq a -> [a]
seqToList s =
  case Seq.viewl s of
    x Seq.:< xs -> x : seqToList xs
    Seq.EmptyL -> []