add crypto errors standard enumeration and some helper.

Crypto/Error.hs

@@ -0,0 +1,12 @@
+-- |
+-- Module      : Crypto.Error
+-- License     : BSD-style
+-- Maintainer  : Vincent Hanquez <vincent@snarc.org>
+-- Stability   : Stable
+-- Portability : Excellent
+--
+module Crypto.Error
+    ( module Crypto.Error.Types
+    ) where
+
+import Crypto.Error.Types

Crypto/Error/Types.hs

@@ -0,0 +1,54 @@
+-- |
+-- Module      : Crypto.Error.Types
+-- License     : BSD-style
+-- Maintainer  : Vincent Hanquez <vincent@snarc.org>
+-- Stability   : stable
+-- Portability : Good
+--
+-- Cryptographic Error enumeration and handling
+--
+{-# LANGUAGE DeriveDataTypeable #-}
+module Crypto.Error.Types
+    ( CryptoError(..)
+    , CryptoFailable(..)
+    ) where
+
+import qualified Control.Exception as E
+import           Data.Data
+
+import           Crypto.Internal.Imports
+
+-- | Enumeration of all possible errors that can be found in this library
+data CryptoError =
+    -- symmetric cipher errors
+      CryptoError_KeySizeInvalid
+    | CryptoError_IvSizeInvalid
+    deriving (Show,Eq,Enum,Data,Typeable)
+
+instance E.Exception CryptoError
+
+-- | A simple Either like type to represent a computation that can fail
+--
+-- 2 possibles values are:
+-- * 'CryptoPassed' : 
+data CryptoFailable a =
+      CryptoPassed a
+    | CryptoFailed CryptoError
+
+instance Functor CryptoFailable where
+    fmap f (CryptoPassed a) = CryptoPassed (f a)
+    fmap _ (CryptoFailed r) = CryptoFailed r
+
+instance Applicative CryptoFailable where
+    pure a = CryptoPassed a
+instance Monad CryptoFailable where
+    return a = CryptoPassed a
+
+throwCryptoError :: CryptoFailable a -> IO a
+throwCryptoError = undefined
+
+eitherCryptoError :: CryptoFailable a -> Either CryptoError a
+eitherCryptoError = undefined
+
+maybeCryptoError :: CryptoFailable a -> Maybe a
+maybeCryptoError = undefined

cryptonite.cabal

@@ -32,6 +32,7 @@ Library
                      Crypto.Cipher.RC4
                      Crypto.Cipher.Types
                      Crypto.Data.AFIS
+                     Crypto.Error
                      Crypto.MAC.Poly1305
                      Crypto.MAC.HMAC
                      Crypto.Number.Basic
@@ -87,6 +88,7 @@ Library
                      Crypto.Cipher.Types.GF
                      Crypto.Cipher.Types.Stream
                      Crypto.Cipher.Types.Utils
+                     Crypto.Error.Types
                      Crypto.Hash.Utils
                      Crypto.Hash.Utils.Cpu
                      Crypto.Hash.Types