module Codec.Compression.Snappy
(
compress
, decompress
) where
import Codec.Compression.Snappy.Internal (check, maxCompressedLength)
import Data.ByteString.Internal (ByteString(..), mallocByteString)
import Data.Word (Word8, Word32)
import Foreign.C.Types (CInt(..), CSize(..))
import Foreign.ForeignPtr (withForeignPtr)
import Foreign.Marshal.Alloc (alloca)
import Foreign.Marshal.Utils (with)
import Foreign.Ptr (Ptr, plusPtr)
import Foreign.Storable (peek)
import System.IO.Unsafe (unsafePerformIO)
import qualified Data.ByteString as B
compress :: ByteString -> ByteString
compress (PS sfp off len) = unsafePerformIO $ do
let dlen0 = maxCompressedLength len
dfp <- mallocByteString dlen0
withForeignPtr sfp $ \sptr ->
withForeignPtr dfp $ \dptr ->
with (fromIntegral dlen0) $ \dlenPtr -> do
c_RawCompress (sptr `plusPtr` off) (fromIntegral len) dptr dlenPtr
(PS dfp 0 . fromIntegral) `fmap` peek dlenPtr
decompress :: ByteString -> ByteString
decompress (PS sfp off slen) = unsafePerformIO $
withForeignPtr sfp $ \sptr0 -> do
let sptr = sptr0 `plusPtr` off
len = fromIntegral slen
alloca $ \dlenPtr -> do
check "decompress" $ c_GetUncompressedLength sptr len dlenPtr
dlen <- fromIntegral `fmap` peek dlenPtr
if dlen == 0
then return B.empty
else do
dfp <- mallocByteString dlen
withForeignPtr dfp $ \dptr -> do
check "decompress" $ c_RawUncompress sptr len dptr
return (PS dfp 0 dlen)
foreign import ccall unsafe "hs_snappy.h _hsnappy_RawCompress"
c_RawCompress :: Ptr a -> CSize -> Ptr Word8 -> Ptr CSize -> IO ()
foreign import ccall unsafe "hs_snappy.h _hsnappy_GetUncompressedLength"
c_GetUncompressedLength :: Ptr a -> CSize -> Ptr Word32 -> IO CInt
foreign import ccall unsafe "hs_snappy.h _hsnappy_RawUncompress"
c_RawUncompress :: Ptr a -> CSize -> Ptr Word8 -> IO CInt