module Data.Digest.Adler32 (
Adler32, adler32
) where
import Foreign
import Foreign.C.Types
import Foreign.ForeignPtr
import GHC.Ptr
import qualified Data.ByteString as S
import qualified Data.ByteString.Internal as BI
import qualified Data.ByteString.Lazy as L
import qualified Data.ByteString.Lazy.Internal as LI
class Adler32 a where
adler32 :: a -> Word32
instance Adler32 S.ByteString where
adler32 = adler32_s
instance Adler32 L.ByteString where
adler32 = adler32_l
instance Adler32 [Word8] where
adler32 = adler32 . L.pack
adler32_s :: S.ByteString -> Word32
adler32_s s = adler32_l (LI.Chunk s LI.Empty)
adler32_l :: L.ByteString -> Word32
adler32_l = LI.foldlChunks updateAdler 0
where updateAdler adler bs = fromIntegral $ adler32_c (fromIntegral adler) buf (fromIntegral len)
where (ptr, offset, len) = BI.toForeignPtr bs
buf = (unsafeForeignPtrToPtr ptr) `plusPtr` offset
foreign import ccall unsafe "zlib.h adler32"
adler32_c :: CInt -> Ptr Word8 -> CInt -> CInt