~alcinnz/fontconfig-pure

ref: 9aee49dd6084ce6deef6099a3b7c27fa0f6c8b1e fontconfig-pure/lib/Graphics/Text/Font/Choose/Internal/FFI.hs -rw-r--r-- 2.1 KiB
9aee49dd — Adrian Cochrane Finish initial redraft 8 months ago 
                                                                                
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module Graphics.Text.Font.Choose.Internal.FFI where

import Data.MessagePack (MessagePack, pack, unpack)
import Foreign.C.String (CString, withCString, peekCString)
import Foreign.Ptr (Ptr)
import Foreign.ForeignPtr (ForeignPtr, withForeignPtr)
import Foreign.Storable (Storable(..))
import Foreign.Marshal.Alloc (alloca)
import Data.Tuple (swap)
import Graphics.Text.Font.Choose.Result (throwNull)
import Data.Maybe (fromJust)

import Data.ByteString.Unsafe (unsafeUseAsCStringLen, unsafePackMallocCStringLen)
import Data.ByteString.Lazy (toStrict, fromStrict)
import System.IO.Unsafe (unsafePerformIO)

withMessageIO :: MessagePack a => (CString -> Int -> IO b) -> a -> IO b
withMessageIO cb a = unsafeUseAsCStringLen (toStrict $ pack a) (uncurry cb)

withMessage :: MessagePack a => (CString -> Int -> b) -> a -> b
withMessage inner arg = unsafePerformIO $ withMessageIO (\x -> return . inner x) arg

fromMessage :: MessagePack a => (Ptr Int -> CString) -> Maybe a
fromMessage inner = unpack $ fromStrict $ unsafePerformIO $ do
    unsafePackMallocCStringLen . swap =<< withPtr (throwNull . inner)

fromMessage0 :: MessagePack a => (Ptr Int -> CString) -> a
fromMessage0 = fromJust . fromMessage

fromMessageIO :: MessagePack a => (Ptr Int -> IO CString) -> IO (Maybe a)
fromMessageIO inner = do
    (a, b) <- withPtr $ \ptr -> do
        throwNull =<< inner ptr
    bs <- unsafePackMallocCStringLen (b, a)
    return $ unpack $ fromStrict bs

fromMessageIO0 :: MessagePack a => (Ptr Int -> IO CString) -> IO a
fromMessageIO0 inner = fromJust <$> fromMessageIO inner

withCString' :: (CString -> a) -> String -> a
withCString' inner = unsafePerformIO . flip withCString (return . inner)

peekCString' :: CString -> String
peekCString' = unsafePerformIO . peekCString

withForeignPtr' :: (Ptr a -> b) -> ForeignPtr a -> b
withForeignPtr' inner arg = unsafePerformIO $ withForeignPtr arg $ return . inner

-- I don't want to pull in all of inline-c for this util!
withPtr :: (Storable a) => (Ptr a -> IO b) -> IO (a, b)
withPtr f = do
  alloca $ \ptr -> do
    x <- f ptr
    y <- peek ptr
    return (y, x)