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bundled/Data/ByteString/Base64/Lazy.hs

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+{-# LANGUAGE CPP #-}
+#if __GLASGOW_HASKELL__ >= 702
+{-# LANGUAGE Trustworthy #-}
+#endif
+
+-- |
+-- Module      : Data.ByteString.Base64.Lazy
+-- Copyright   : (c) 2012 Ian Lynagh
+--
+-- License     : BSD-style
+-- Maintainer  : Emily Pillmore <emilypi@cohomolo.gy>,
+--               Herbert Valerio Riedel <hvr@gnu.org>,
+--               Mikhail Glushenkov <mikhail.glushenkov@gmail.com>
+-- Stability   : experimental
+-- Portability : GHC
+--
+-- Fast and efficient encoding and decoding of base64-encoded
+-- lazy bytestrings.
+--
+-- @since 1.0.0.0
+module Data.ByteString.Base64.Lazy
+    (
+      encode
+    , decode
+    , decodeLenient
+    ) where
+
+import Data.ByteString.Base64.Internal
+import qualified Data.ByteString.Base64     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
+-- <http://tools.ietf.org/rfc/rfc4648 RFC 4648>.
+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
+-- <http://tools.ietf.org/rfc/rfc4648 RFC 4648>, 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 = isDigit c || isAsciiUpper c || isAsciiLower c
+                                 || c == '+' || c == '/'