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52 lines
2.1 KiB
Plaintext
52 lines
2.1 KiB
Plaintext
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module Network.GRPC.Unsafe.Slice where
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#include <grpc/impl/codegen/slice.h>
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#include <grpc_haskell.h>
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import qualified Data.ByteString as B
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import Foreign.C.String
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import Foreign.C.Types
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import Foreign.Ptr
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-- | A 'Slice' is gRPC's string type. We can easily convert these to and from
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-- ByteStrings. This type is a pointer to a C type.
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{#pointer *gpr_slice as Slice newtype #}
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-- TODO: we could also represent this type as 'Ptr Slice', by doing this:
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-- newtype Slice = Slice {#type gpr_slice#}
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-- This would have no practical effect, but it would communicate intent more
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-- clearly by emphasizing that the type is indeed a pointer and that the data
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-- it is pointing to might change/be destroyed after running IO actions. To make
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-- the change, we would just need to change all occurrences of 'Slice' to
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-- 'Ptr Slice' and add 'castPtr' in and out marshallers.
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-- This seems like the right way to do it, but c2hs doesn't make it easy, so
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-- maybe the established idiom is to do what c2hs does.
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-- | Get the length of a slice.
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{#fun gpr_slice_length_ as ^ {`Slice'} -> `CULong'#}
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-- | Returns a pointer to the start of the character array contained by the
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-- slice.
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{#fun gpr_slice_start_ as ^ {`Slice'} -> `Ptr CChar' castPtr #}
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{#fun gpr_slice_from_copied_string_ as ^ {`CString'} -> `Slice'#}
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-- | Properly cleans up all memory used by a 'Slice'. Danger: the Slice should
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-- not be used after this function is called on it.
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{#fun free_slice as ^ {`Slice'} -> `()'#}
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-- | Copies a 'Slice' to a ByteString.
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-- TODO: there are also non-copying unsafe ByteString construction functions.
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-- We could gain some speed by using them.
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-- idea would be something :: (ByteString -> Response) -> IO () that handles
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-- getting and freeing the slice behind the scenes.
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sliceToByteString :: Slice -> IO B.ByteString
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sliceToByteString slice = do
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len <- fmap fromIntegral $ gprSliceLength slice
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str <- gprSliceStart slice
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B.packCStringLen (str, len)
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-- | Copies a 'ByteString' to a 'Slice'.
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byteStringToSlice :: B.ByteString -> IO Slice
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byteStringToSlice bs = B.useAsCString bs gprSliceFromCopiedString
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