add an helper to use the compression context easily

Network/TLS/State.hs

@@ -21,6 +21,7 @@ module Network.TLS.State
 	, newTLSState
 	, genTLSRandom
 	, withTLSRNG
+	, withCompression
 	, assert -- FIXME move somewhere else (Internal.hs ?)
 	, updateStatusHs
 	, updateStatusCC
@@ -175,6 +176,13 @@ withTLSRNG (StateRNG rng) f = case f rng of
 	Left err        -> Left err
 	Right (a, rng') -> Right (a, StateRNG rng')
 
+withCompression :: (Compression -> (Compression, a)) -> TLSSt a
+withCompression f = do
+	compression <- stCompression <$> get
+	let (nc, a) = f compression
+	modify (\st -> st { stCompression = nc })
+	return a
+
 genTLSRandom :: (MonadState TLSState m, MonadError TLSError m) => Int -> m Bytes
 genTLSRandom n = do
 	st <- get