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{-# LANGUAGE CPP #-}
#if __GLASGOW_HASKELL__ >= 702
{-# LANGUAGE Trustworthy #-}
#endif
-- |
-- Module : Data.ByteString.Base64.URL.Lazy
-- Copyright : (c) 2012 Ian Lynagh
--
-- License : BSD-style
-- Maintainer : bos@serpentine.com
-- Stability : experimental
-- Portability : GHC
--
-- Fast and efficient encoding and decoding of base64-encoded
-- lazy bytestrings.
module Data.ByteString.Base64.URL.Lazy
(
encode
, decode
, decodeLenient
) where
import Data.ByteString.Base64.Internal
import qualified Data.ByteString.Base64.URL as B64
import qualified Data.ByteString as S
import qualified Data.ByteString.Lazy as L
import qualified Data.ByteString.Lazy.Char8 as LC
import Data.Char
-- | Encode a string into base64 form. The result will always be a
-- multiple of 4 bytes in length.
encode :: L.ByteString -> L.ByteString
encode = L.fromChunks . map B64.encode . reChunkIn 3 . L.toChunks
-- | Decode a base64-encoded string. This function strictly follows
-- the specification in RFC 4648,
-- <http://www.apps.ietf.org/rfc/rfc4648.html>.
decode :: L.ByteString -> Either String L.ByteString
decode b = -- Returning an Either type means that the entire result will
-- need to be in memory at once anyway, so we may as well
-- keep it simple and just convert to and from a strict byte
-- string
-- TODO: Use L.{fromStrict,toStrict} once we can rely on
-- a new enough bytestring
case B64.decode $ S.concat $ L.toChunks b of
Left err -> Left err
Right b' -> Right $ L.fromChunks [b']
-- | Decode a base64-encoded string. This function is lenient in
-- following the specification from RFC 4648,
-- <http://www.apps.ietf.org/rfc/rfc4648.html>, and will not generate
-- parse errors no matter how poor its input.
decodeLenient :: L.ByteString -> L.ByteString
decodeLenient = L.fromChunks . map B64.decodeLenient . reChunkIn 4 . L.toChunks
. LC.filter goodChar
where -- We filter out and '=' padding here, but B64.decodeLenient
-- handles that
goodChar c = isAlphaNum c || c == '-' || c == '_'
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