{-# LANGUAGE DeriveGeneric #-} -- | Internals, exposed mostly for potential use by testsuites and benchmarks. -- -- __Not recommended to be used from within other independent libraries.__ module Data.Binary.Typed.Internal ( -- * 'Typed' Typed(..) , TypeInformation(..) , Hash32(..) , Hash64(..) , typed , makeTypeInformation , TypeFormat(..) , getFormat , typecheck , erase , preserialize -- * 'TypeRep' , TypeRep(..) , stripTypeRep , unStripTypeRep , hashType32 , hashType64 -- * 'TyCon' , TyCon(..) , stripTyCon , unStripTyCon ) where import GHC.Generics import Text.Printf -- import qualified Data.ByteString as BS import qualified Data.ByteString.Lazy as BSL import Data.Typeable (Typeable, typeOf) import qualified Data.Typeable as Ty import Data.Binary -- Crypto stuff for hashing import qualified Data.Digest.Murmur32 as H32 import qualified Data.Digest.Murmur64 as H64 -- ^ Type information stored alongside a value to be serialized, so that the -- recipient can do consistency checks. See 'TypeFormat' for more detailed -- information on the fields. data TypeInformation = Untyped' | Hashed32' Hash32 | Hashed64' Hash64 | Shown' Hash32 String | Full' TypeRep | Cached' BSL.ByteString deriving (Eq, Ord, Show, Generic) instance Binary TypeInformation -- | Extract which 'TypeFormat' was used to create a certain 'TypeInformation'. -- -- If the type is 'Cached'', then the contained information is assumed -- well-formed. In the public API, this is safe to do, since only well-typed -- 'Typed' values can be created in the first place. getFormat :: TypeInformation -> TypeFormat getFormat (Untyped' {}) = Untyped getFormat (Hashed32' {}) = Hashed32 getFormat (Hashed64' {}) = Hashed64 getFormat (Shown' {}) = Shown getFormat (Full' {}) = Full getFormat (Cached' bs) = getFormat (decode bs) -- | A hash value of a 'TypeRep'. Currently a 32-bit value created using -- the MurmurHash2 algorithm. newtype Hash32 = Hash32 Word32 deriving (Eq, Ord, Show, Generic) instance Binary Hash32 -- | A hash value of a 'TypeRep'. Currently a 64-bit value created using -- the MurmurHash2 algorithm. newtype Hash64 = Hash64 Word64 deriving (Eq, Ord, Show, Generic) instance Binary Hash64 -- | A value suitable to be typechecked using the contained extra type -- information. data Typed a = Typed TypeInformation a -- ^ Using this data constructor directly is unsafe, as it allows -- construction of ill-typed 'Typed' data. Use the 'typed' smart -- constructor unless you really need 'Typed'. -- | "typed \<format\> \<value\>" instance Show a => Show (Typed a) where show (Typed ty x) = printf "typed %s (%s)" (show (getFormat ty)) (show x) -- | Ensures data is decoded as the appropriate type with high or total -- confidence (depending on with what 'TypeFormat' the 'Typed' was -- constructed). instance (Binary a, Typeable a) => Binary (Typed a) where get = do (ty, value) <- get either fail return (typecheck (Typed ty value)) -- NB: 'fail' is safe in Get Monad put (Typed ty value) = put (ty, value) -- | Sometimes it can be beneficial to serialize the type information in -- advance, so that the maybe costly serialization step does not have to be -- repeated on every invocation of 'encode'. Preserialization comes at a price -- though, as the directly contained 'BSL.ByteString' requires its length to -- be included in the final serialization, yielding a 8-byte overhead for the -- required 'Data.Int.Int64', and one for the tag of what was serialized -- (\"shown or full?\"). -- -- This function calculates the serialized version of 'TypeInformation' in -- cases where the required 9 bytes are negligible (determined by an -- arbitrary threshold, currently 10*9 bytes). -- -- Used to make 'Data.Binary.Typed.encodeTyped' more efficient; the source -- there also makes a good usage example. preserialize :: TypeInformation -> TypeInformation preserialize x@(Cached' _) = x preserialize x@(Untyped' ) = x preserialize x@(Hashed32' _) = x preserialize x@(Hashed64' _) = x -- Explicit cases for Shown' and Full' so exhaustiveness can be checked when -- new constructors are added. (The default pattern of just "x" would do right -- now as well, but not provide that.) preserialize x@(Shown' _ _) = preserialize' x preserialize x@(Full' _) = preserialize' x -- | Preserializes type information if its encoded byte length is larger than -- an arbitrary threshold. Less efficient than 'preserialize' since it -- always preserializes and always calculates the encoded version no matter -- what. preserialize' :: TypeInformation -> TypeInformation preserialize' x | BSL.length encoded > 10*9 = Cached' encoded | otherwise = x where encoded = encode x -- | Different ways of including/verifying type information of serialized -- messages. data TypeFormat = -- | Include no type information. -- -- * Requires one byte more compared to using 'Binary' directly -- (to tag the data as untyped, required for the decoding step). Untyped -- | Compare types by their hash values (using the MurmurHash2 -- algorithm). -- -- * Requires five bytes more compared to using 'Binary' directly for -- the type information (one to tag as 'Hashed32', four for the -- hash value) -- -- * Subject to false positive due to hash collisions, although in -- practice this should almost never happen. -- -- * Type errors cannot tell the provided type ("Expected X, received -- type with hash H") | Hashed32 -- | Like 'Hashed32', but uses a 64-bit hash value. -- -- * Requires nine bytes more compared to using 'Binary'. -- -- * Hash collisions are even less likely to occur than with -- 'Hashed32'. | Hashed64 -- | Compare 'String' representation of types, obtained by calling -- 'show' on the 'TypeRep', and also include a hash value -- (like 'Hashed32'). The former is mostly for readable error -- messages, the latter provides better collision resistance. -- -- * Data size larger than 'Hashed32', but usually smaller than -- 'Full'. -- -- * Both the hash and the shown type must match to satisfy the -- typechecker. -- -- * Useful type errors ("expected X, received Y"). All types are -- shown unqualified though, making @Foo.X@ and @Bar.X@ look -- identical in error messages. Remember this when you get a -- seemingly silly error "expected Foo, but given Foo". | Shown -- | Compare the full representation of a data type. -- -- * More verbose than 'Hashed' and 'Shown'. As a rule of thumb, -- transmitted data is roughly the same as 'Shown', but all names -- are fully qualified (package, module, type name). -- * Correct comparison (no false positives). An semi-exception here -- is when types change between package versions: -- @package-1.0 Foo.X@ and @package-1.1 Foo.X@ count as the same -- type. -- * Useful type errors ("expected X, received Y"). All types are -- shown unqualified though, making @Foo.X@ and @Bar.X@ look -- identical in error messages. Remember this when you get a -- seemingly silly error "expected Foo, but given Foo". | Full deriving (Eq, Ord, Show) -- | Construct a 'Typed' value using the chosen type format. -- -- Example: -- -- @ -- value = 'typed' 'Full' ("hello", 1 :: 'Int', 2.34 :: 'Double') -- encded = 'encode' value -- @ -- -- The decode site can now verify whether decoding happens with the right type. typed :: Typeable a => TypeFormat -> a -> Typed a typed format x = Typed (makeTypeInformation format (typeOf x)) x -- | Create the 'TypeInformation' to be stored inside a 'Typed' value from -- a 'Ty.TypeRep'. makeTypeInformation :: TypeFormat -> Ty.TypeRep -> TypeInformation makeTypeInformation format ty = case format of Untyped -> Untyped' Hashed32 -> Hashed32' (hashType32 ty) Hashed64 -> Hashed64' (hashType64 ty) Shown -> Shown' (hashType32 ty) (show ty) Full -> Full' (stripTypeRep ty) -- | Extract the value of a 'Typed', i.e. strip off the explicit type -- information. -- -- This function is safe to use for all 'Typed' values created by the public -- API, since all construction sites ensure the actual type matches the -- contained type description. -- -- @ -- 'erase' ('typed' format x) == x -- @ erase :: Typed a -> a erase (Typed _ty value) = value -- | Typecheck a 'Typed'. Returns the (well-typed) input, or an error message -- if the types don't work out. typecheck :: Typeable a => Typed a -> Either String (Typed a) typecheck ty@(Typed typeInformation x) = case typeInformation of Cached' cache -> decode' cache >>= \ty' -> typecheck (Typed ty' x) Full' full | exFull /= full -> Left (fullError full) Hashed32' hash32 | exHash32 /= hash32 -> Left (hashError exHash32 hash32) Hashed64' hash64 | exHash64 /= hash64 -> Left (hashError exHash64 hash64) Shown' hash32 str | (exHash32, exShow) /= (hash32, str) -> Left (shownError hash32 str) _no_type_error -> Right ty where -- ex = expected exType = typeOf x exHash32 = hashType32 exType exHash64 = hashType64 exType exShow = show exType exFull = stripTypeRep exType hashError eHash hash = printf pat exShow (show eHash) (show hash) where pat = "Type error: expected type %s with hash %s,\ \ but received data with hash %s" shownError hash str = printf pat exShow (show exHash32) str (show hash) where pat = "Type error: expected type %s and hash %s,\ \ but received data with type %s and hash %s" fullError full = printf pat exShow (show full) where pat = "Type error: expected type %s,\ \ but received data with type %s" decode' bs = case decodeOrFail bs of Left (_,_,err) -> Left ("Cache error! " ++ err) Right (_,_,val) -> Right val -- | Hash a 'Ty.TypeRep' to a 32-bit digest. hashType32 :: Ty.TypeRep -> Hash32 hashType32 = Hash32 . H32.asWord32 . H32.hash32 . stripTypeRep -- | Hash a 'Ty.TypeRep' to a 64-bit digest. hashType64 :: Ty.TypeRep -> Hash64 hashType64 = Hash64 . H64.asWord64 . H64.hash64 . stripTypeRep -- | 'Ty.TypeRep' without the (internal) fingerprint. data TypeRep = TypeRep TyCon [TypeRep] deriving (Eq, Ord, Generic) instance Binary TypeRep instance Show TypeRep where show = show . unStripTypeRep instance H32.Hashable32 TypeRep where hash32Add (TypeRep tycon args) = H32.hash32Add (tycon, args) instance H64.Hashable64 TypeRep where hash64Add (TypeRep tycon args) = H64.hash64Add (tycon, args) -- | 'Ty.TyCon' without the (internal) fingerprint. data TyCon = TyCon String String String -- ^ Package, module, constructor name deriving (Eq, Ord, Generic) instance Binary TyCon instance Show TyCon where show = show . unStripTyCon instance H32.Hashable32 TyCon where hash32Add (TyCon p m c) = H32.hash32Add (p, m, c) instance H64.Hashable64 TyCon where hash64Add (TyCon p m c) = H64.hash64Add (p, m, c) -- | Strip a 'Ty.TypeRep' off the fingerprint. Inverse of 'unStripTypeRep'. stripTypeRep :: Ty.TypeRep -> TypeRep stripTypeRep typerep = TypeRep (stripTyCon tycon) (map stripTypeRep args) where (tycon, args) = Ty.splitTyConApp typerep -- | Add a fingerprint to a 'TypeRep'. Inverse of 'stripTypeRep'. unStripTypeRep :: TypeRep -> Ty.TypeRep unStripTypeRep (TypeRep tyCon args) = Ty.mkTyConApp (unStripTyCon tyCon) (map unStripTypeRep args) -- | Strip a 'Ty.TyCon' off the fingerprint. Inverse of 'unStripTyCon'. stripTyCon :: Ty.TyCon -> TyCon stripTyCon tycon = TyCon (Ty.tyConPackage tycon) (Ty.tyConModule tycon) (Ty.tyConName tycon) -- The Typeable API doesn't expose the -- TyCon constructor, so pattern matching -- is not possible here (without depending -- on Typeable.Internal). -- | Add a fingerprint to a 'TyCon'. Inverse of 'stripTyCon'. unStripTyCon :: TyCon -> Ty.TyCon unStripTyCon (TyCon p m n) = Ty.mkTyCon3 p m n -- package, module, name