54 lines
1.4 KiB
Haskell
54 lines
1.4 KiB
Haskell
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-- | Marshall from a Rust-side allocated buffer
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--
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-- Intended for unqualified import.
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module Foreign.Rust.Marshall.External (
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fromExternalBorsh
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) where
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import Codec.Borsh
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import Control.Exception
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import Data.Typeable
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import Data.Word
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import Foreign.C
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import Foreign.Concurrent
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import Foreign.Ptr
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import qualified Data.ByteString.Internal as Strict
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import Foreign.Rust.Marshall.Util
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data External
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foreign import ccall "haskell_ffi_external_ptr"
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externalPtr
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:: Ptr External -> Ptr Word8
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foreign import ccall "haskell_ffi_external_len"
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externalLen
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:: Ptr External -> CSize
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foreign import ccall "haskell_ffi_external_free"
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externalFree
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:: Ptr External -> IO ()
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-- | Internal auxiliary: cast pointer
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--
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-- For ease of integration with c2hs, 'fromExternalBorsh' takes a @Ptr ()@ as
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-- input instead of the more accurate @Ptr External@.
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castToExternal :: Ptr () -> Ptr External
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castToExternal = castPtr
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-- | Output marshaller for values stored in Rust-allocated buffer
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--
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-- Should be used together with the Rust function @marshall_to_haskell_external@
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-- (from @haskell-ffi@).
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fromExternalBorsh :: (FromBorsh a, Typeable a) => Ptr () -> IO a
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fromExternalBorsh (castToExternal -> ptr) = do
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len <- evaluate $ fromIntegral $ externalLen ptr
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fptr <- newForeignPtr (externalPtr ptr) (externalFree ptr)
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let bs :: Strict.ByteString
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bs = Strict.PS fptr 0 len
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return $ deserialiseStrictOrPanic bs
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