base64-bytestring-0.1.0.0: Data/ByteString/Base64.hs
{-# LANGUAGE BangPatterns #-}
-- |
-- Module : Data.ByteString.Base64
-- Copyright : (c) 2010 Bryan O'Sullivan
--
-- License : BSD-style
-- Maintainer : bos@serpentine.com
-- Stability : experimental
-- Portability : GHC
--
-- Fast and efficient encoding and decoding of base64-encoded strings.
module Data.ByteString.Base64
(
encode
, decode
, decodeLenient
, joinWith
) where
import Data.Bits ((.|.), (.&.), shiftL, shiftR)
import qualified Data.ByteString as B
import Data.ByteString.Internal (ByteString(..), mallocByteString, memcpy,
unsafeCreate)
import Data.ByteString.Unsafe (unsafeIndex)
import Data.Word (Word8, Word16, Word32)
import Foreign.ForeignPtr (ForeignPtr, mallocForeignPtrArray, withForeignPtr)
import Foreign.Ptr (Ptr, castPtr, minusPtr, plusPtr)
import Foreign.Storable (peek, peekElemOff, poke, pokeElemOff)
import System.IO.Unsafe (unsafePerformIO)
peek8 :: Ptr Word8 -> IO Word8
peek8 = peek
poke8 :: Ptr Word8 -> Word8 -> IO ()
poke8 = poke
peek8_32 :: Ptr Word8 -> IO Word32
peek8_32 = fmap fromIntegral . peek8
-- | Encode a string into base64 form. The result will always be a
-- multiple of 4 bytes in length.
encode :: ByteString -> ByteString
encode (PS sfp soff slen) = unsafePerformIO $ do
let dlen = ((slen + 2) `div` 3) * 4
dfp <- mallocByteString dlen
withForeignPtr alfaFP $ \aptr ->
withForeignPtr encodeTable $ \ep ->
withForeignPtr sfp $ \sptr -> do
let aidx n = peek8 (aptr `plusPtr` n)
sEnd = sptr `plusPtr` (slen + soff)
fill !dp !sp
| sp `plusPtr` 2 >= sEnd = complete (castPtr dp) sp
| otherwise = {-# SCC "encode/fill" #-} do
i <- peek8_32 sp
j <- peek8_32 (sp `plusPtr` 1)
k <- peek8_32 (sp `plusPtr` 2)
let w = (i `shiftL` 16) .|. (j `shiftL` 8) .|. k
enc = peekElemOff ep . fromIntegral
poke dp =<< enc (w `shiftR` 12)
poke (dp `plusPtr` 2) =<< enc (w .&. 0xfff)
fill (dp `plusPtr` 4) (sp `plusPtr` 3)
complete dp sp
| sp == sEnd = return ()
| otherwise = {-# SCC "encode/complete" #-} do
let peekSP n f = (f . fromIntegral) `fmap` peek8 (sp `plusPtr` n)
twoMore = sp `plusPtr` 2 == sEnd
equals = 0x3d :: Word8
{-# INLINE equals #-}
a <- peekSP 0 ((`shiftR` 2) . (.&. 0xfc))
b <- peekSP 0 ((`shiftL` 4) . (.&. 0x03))
!b' <- if twoMore
then peekSP 1 ((.|. b) . (`shiftR` 4) . (.&. 0xf0))
else return b
poke8 dp =<< aidx a
poke8 (dp `plusPtr` 1) =<< aidx b'
c <- if twoMore
then aidx =<< peekSP 1 ((`shiftL` 2) . (.&. 0x0f))
else return equals
poke8 (dp `plusPtr` 2) c
poke8 (dp `plusPtr` 3) equals
withForeignPtr dfp $ \dptr ->
fill (castPtr dptr) (sptr `plusPtr` soff)
return $! PS dfp 0 dlen
-- | Efficiently intersperse a terminator string into another at
-- regular intervals, and terminate the input with it.
--
-- Examples:
--
-- > joinWith "|" 2 "----" = "--|--|"
--
-- > joinWith "\r\n" 3 "foobarbaz" = "foo\r\nbar\r\nbaz\r\n"
joinWith :: ByteString -- ^ String to intersperse and end with
-> Int -- ^ Interval at which to intersperse, in bytes
-> ByteString -- ^ String to transform
-> ByteString
joinWith brk@(PS bfp boff blen) every bs@(PS sfp soff slen)
| every <= 0 = error "invalid interval"
| blen <= 0 = bs
| B.null bs = brk
| otherwise =
unsafeCreate dlen $ \dptr ->
withForeignPtr bfp $ \bptr -> do
withForeignPtr sfp $ \sptr -> do
let bp = bptr `plusPtr` boff
let dEnd = dptr `plusPtr` dlen
loop !dp !sp | dp >= dEnd = return ()
| otherwise = do
let n = min every (dEnd `minusPtr` dp)
memcpy dp sp (fromIntegral n)
memcpy (dp `plusPtr` n) bp (fromIntegral blen)
loop (dp `plusPtr` (n + blen)) (sp `plusPtr` every)
loop dptr (sptr `plusPtr` soff)
where dlen = slen + blen * numBreaks
numBreaks = slen `div` every
-- | Decode a base64-encoded string. This function strictly follows
-- the specification in RFC 4648,
-- <http://www.apps.ietf.org/rfc/rfc4648.html>.
decode :: ByteString -> Either String ByteString
decode (PS sfp soff slen)
| drem /= 0 = Left "invalid padding"
| dlen <= 0 = Right B.empty
| otherwise = unsafePerformIO $ do
dfp <- mallocByteString dlen
withForeignPtr decodeFP $ \decptr -> do
let finish dbytes = return . Right $! if dbytes > 0
then PS dfp 0 dbytes
else B.empty
bail = return . Left
withForeignPtr sfp $ \sptr -> do
let sEnd = sptr `plusPtr` (slen + soff)
look p = do
ix <- fromIntegral `fmap` peek8 p
v <- peek8 (decptr `plusPtr` ix)
return $! fromIntegral v :: IO Word32
fill !dp !sp !n
| sp >= sEnd = finish n
| otherwise = {-# SCC "decode/fill" #-} do
a <- look sp
b <- look (sp `plusPtr` 1)
c <- look (sp `plusPtr` 2)
d <- look (sp `plusPtr` 3)
let w = (a `shiftL` 18) .|. (b `shiftL` 12) .|.
(c `shiftL` 6) .|. d
if a == done || b == done
then bail $ "invalid padding near offset " ++
show (sp `minusPtr` sptr)
else if a .|. b .|. c .|. d == x
then bail $ "invalid base64 encoding near offset " ++
show (sp `minusPtr` sptr)
else do
poke8 dp $ fromIntegral (w `shiftR` 16)
if c == done
then finish $ n + 1
else do
poke8 (dp `plusPtr` 1) $ fromIntegral (w `shiftR` 8)
if d == done
then finish $! n + 2
else do
poke8 (dp `plusPtr` 2) $ fromIntegral w
fill (dp `plusPtr` 3) (sp `plusPtr` 4) (n+3)
withForeignPtr dfp $ \dptr ->
fill dptr (sptr `plusPtr` soff) 0
where (di,drem) = slen `divMod` 4
dlen = di * 3
data D = D { dNext :: {-# UNPACK #-} !(Ptr Word8)
, dValue :: {-# UNPACK #-} !Word32 }
-- | 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 :: ByteString -> ByteString
decodeLenient (PS sfp soff slen)
| dlen <= 0 = B.empty
| otherwise = unsafePerformIO $ do
dfp <- mallocByteString dlen
dbytes <- withForeignPtr decodeFP $ \decptr ->
withForeignPtr sfp $ \sptr -> do
let sEnd = sptr `plusPtr` (slen + soff)
fill !dp !sp !n
| sp >= sEnd = return n
| otherwise = {-# SCC "decodeLenient/fill" #-} do
let look skipPad = go
where
go p | p >= sEnd = return $! D (sEnd `plusPtr` (-1)) done
| otherwise = {-# SCC "decodeLenient/look" #-} do
ix <- fromIntegral `fmap` peek8 p
v <- peek8 (decptr `plusPtr` ix)
if v == x || (v == done && skipPad)
then go (p `plusPtr` 1)
else return $! D (p `plusPtr` 1) (fromIntegral v)
!a <- look True sp
!b <- look True (dNext a)
!c <- look False (dNext b)
!d <- look False (dNext c)
let w = (dValue a `shiftL` 18) .|. (dValue b `shiftL` 12) .|.
(dValue c `shiftL` 6) .|. dValue d
if dValue a == done || dValue b == done
then return n
else do
poke8 dp $ fromIntegral (w `shiftR` 16)
if dValue c == done
then return $! n + 1
else do
poke8 (dp `plusPtr` 1) $ fromIntegral (w `shiftR` 8)
if dValue d == done
then return $! n + 2
else do
poke8 (dp `plusPtr` 2) $ fromIntegral w
fill (dp `plusPtr` 3) (dNext d) (n+3)
withForeignPtr dfp $ \dptr ->
fill dptr (sptr `plusPtr` soff) 0
return $! if dbytes > 0
then PS dfp 0 dbytes
else B.empty
where dlen = ((slen + 3) `div` 4) * 3
alphabet :: ByteString
alfaFP :: ForeignPtr Word8
alphabet@(PS alfaFP _ _) = B.pack $ [65..90] ++ [97..122] ++ [48..57] ++ [43,47]
{-# NOINLINE alphabet #-}
encodeTable :: ForeignPtr Word16
encodeTable = unsafePerformIO $ do
fp <- mallocForeignPtrArray 4096
let ix = fromIntegral . unsafeIndex alphabet
withForeignPtr fp $ \p ->
sequence_ [ pokeElemOff p (j*64+k) ((ix k `shiftL` 8) .|. ix j)
| j <- [0..64], k <- [0..64] ]
return fp
{-# NOINLINE encodeTable #-}
decodeFP :: ForeignPtr Word8
PS decodeFP _ _ = B.pack $ replicate 43 x ++ [62,x,x,x,63] ++ [52..61] ++ [x,x,
x,done,x,x,x] ++ [0..25] ++ [x,x,x,x,x,x] ++ [26..51] ++ replicate 133 x
{-# NOINLINE decodeFP #-}
x :: Integral a => a
x = 255
{-# INLINE x #-}
done :: Integral a => a
done = 99
{-# INLINE done #-}