Source

base16-bytestring / Data / ByteString / Base16.hs

Vincent Hanquez 514b05d 
Bryan O'Sullivan 5c297dc 



















Vincent Hanquez 514b05d 
Bryan O'Sullivan 3ffaa35 
Bryan O'Sullivan 5c297dc 


Vincent Hanquez 514b05d 


Bryan O'Sullivan 5c297dc 
Bryan O'Sullivan bdf921f 





Bryan O'Sullivan 5c297dc 

Bryan O'Sullivan bdf921f 

Bryan O'Sullivan 5c297dc 








Vincent Hanquez 514b05d 

Bryan O'Sullivan 5c297dc 
Vincent Hanquez 514b05d 



































Bryan O'Sullivan 5c297dc 
Bryan O'Sullivan bdf921f 








Bryan O'Sullivan 5c297dc 






























{-# LANGUAGE BangPatterns, MagicHash #-}

-- |
-- Module      : Data.ByteString.Base16
-- Copyright   : (c) 2011 MailRank, Inc.
--
-- License     : BSD
-- Maintainer  : bos@mailrank.com
-- Stability   : experimental
-- Portability : GHC
--
-- Fast and efficient encoding and decoding of base16-encoded strings.

module Data.ByteString.Base16
    (
      encode
    , decode
    ) where

import Data.ByteString.Char8 (empty)
import Data.ByteString.Internal (ByteString(..), createAndTrim', unsafeCreate)
import Data.Bits (shiftL)
import Foreign.ForeignPtr (ForeignPtr, withForeignPtr)
import Foreign.Ptr (Ptr, minusPtr, plusPtr)
import Foreign.Storable (peek, poke)
import System.IO.Unsafe (unsafePerformIO)
import GHC.Prim
import GHC.Types
import GHC.Word

-- | Encode a string into base16 form.  The result will always be a
-- multiple of 2 bytes in length.
--
-- Example:
--
-- > encode "foo"  == "666f6f"
encode :: ByteString -> ByteString
encode (PS sfp soff slen)
    | slen > maxBound `div` 2 =
        error "Data.ByteString.Base16.encode: input too long"
    | otherwise = unsafeCreate (slen*2) $ \dptr ->
                    withForeignPtr sfp $ \sptr ->
                      enc (sptr `plusPtr` soff) dptr
 where
  enc sptr = go sptr where
    e = sptr `plusPtr` slen
    go s d | s == e = return ()
           | otherwise = do
      x <- peek8 s
      poke d (tlookup tableHi x)
      poke (d `plusPtr` 1) (tlookup tableLo x)
      go (s `plusPtr` 1) (d `plusPtr` 2)
    tlookup :: Addr# -> Int -> Word8
    tlookup table (I# index) = W8# (indexWord8OffAddr# table index)
    !tableLo =
      "\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66\
      \\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x61\x62\x63\x64\x65\x66"#
    !tableHi =
      "\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\
      \\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\x31\
      \\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\x32\
      \\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\x33\
      \\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\x34\
      \\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\x35\
      \\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\x36\
      \\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\x37\
      \\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\x38\
      \\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\x39\
      \\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\x61\
      \\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\x62\
      \\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\x63\
      \\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\x64\
      \\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\x65\
      \\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66\x66"#

-- | Decode a string from base16 form. The first element of the
-- returned tuple contains the decoded data. The second element starts
-- at the first invalid base16 sequence in the original string.
--
-- Examples:
--
-- > decode "666f6f"  == ("foo", "")
-- > decode "66quux"  == ("f", "quux")
-- > decode "666quux" == ("f", "6quux")
decode :: ByteString -> (ByteString, ByteString)
decode (PS sfp soff slen) =
  unsafePerformIO . createAndTrim' (slen `div` 2) $ \dptr ->
      withForeignPtr sfp $ \sptr ->
        dec (sptr `plusPtr` soff) dptr
 where
  dec sptr = go sptr where
    e = sptr `plusPtr` if odd slen then slen - 1 else slen
    go s d | s == e = let len = e `minusPtr` sptr
                      in return (0, len `div` 2, ps sfp (soff+len) (slen-len))
           | otherwise = do
      let hex w
              | w >= 48 && w <= 57  = w - 48
              | w >= 97 && w <= 102 = w - 97 + 10
              | w >= 65 && w <= 70  = w - 65 + 10
              | otherwise           = 0xff
      hi <- hex `fmap` peek8 s
      lo <- hex `fmap` peek8 (s `plusPtr` 1)
      if lo == 0xff || hi == 0xff
        then let len = s `minusPtr` sptr
             in return (0, len `div` 2, ps sfp (soff+len) (slen-len))
        else do
          poke d . fromIntegral $ lo + (hi `shiftL` 4)
          go (s `plusPtr` 2) (d `plusPtr` 1)

peek8 :: Ptr Word8 -> IO Int
peek8 p = fromIntegral `fmap` peek p

ps :: ForeignPtr Word8 -> Int -> Int -> ByteString
ps fp off len
    | len <= 0 = empty
    | otherwise = PS fp off len