{-# OPTIONS_HADDOCK hide #-} {-# LANGUAGE ExistentialQuantification #-} -- | -- Module : Network.TLS.Compression -- License : BSD-style -- Maintainer : Vincent Hanquez <vincent@snarc.org> -- Stability : experimental -- Portability : unknown -- module Network.TLS.Compression ( CompressionC(..) , Compression(..) , CompressionID , nullCompression , NullCompression -- * member redefined for the class abstraction , compressionID , compressionDeflate , compressionInflate -- * helper , compressionIntersectID ) where import Data.Word import Network.TLS.Types (CompressionID) import Data.ByteString (ByteString) import Control.Arrow (first) -- | supported compression algorithms need to be part of this class class CompressionC a where compressionCID :: a -> CompressionID compressionCDeflate :: a -> ByteString -> (a, ByteString) compressionCInflate :: a -> ByteString -> (a, ByteString) -- | every compression need to be wrapped in this, to fit in structure data Compression = forall a . CompressionC a => Compression a -- | return the associated ID for this algorithm compressionID :: Compression -> CompressionID compressionID (Compression c) = compressionCID c -- | deflate (compress) a bytestring using a compression context and return the result -- along with the new compression context. compressionDeflate :: ByteString -> Compression -> (Compression, ByteString) compressionDeflate bytes (Compression c) = first Compression $ compressionCDeflate c bytes -- | inflate (decompress) a bytestring using a compression context and return the result -- along the new compression context. compressionInflate :: ByteString -> Compression -> (Compression, ByteString) compressionInflate bytes (Compression c) = first Compression $ compressionCInflate c bytes instance Show Compression where show = show . compressionID instance Eq Compression where (==) c1 c2 = compressionID c1 == compressionID c2 -- | intersect a list of ids commonly given by the other side with a list of compression -- the function keeps the list of compression in order, to be able to find quickly the prefered -- compression. compressionIntersectID :: [Compression] -> [Word8] -> [Compression] compressionIntersectID l ids = filter (\c -> elem (compressionID c) ids) l -- | This is the default compression which is a NOOP. data NullCompression = NullCompression instance CompressionC NullCompression where compressionCID _ = 0 compressionCDeflate s b = (s, b) compressionCInflate s b = (s, b) -- | default null compression nullCompression :: Compression nullCompression = Compression NullCompression