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Foreign.Marshal.Utils

Portability | portable
Stability | provisional
Maintainer | ffi@haskell.org

Contents

General marshalling utilities
  Combined allocation and marshalling
  Marshalling of Boolean values (non-zero corresponds to `True`)
  Marshalling of Maybe values
  Marshalling lists of storable objects
  Haskellish interface to memcpy and memmove

Description
Utilities for primitive marshaling
Synopsis

with :: Storable a => a -> (Ptr a -> IO b) -> IO b
new :: Storable a => a -> IO (Ptr a)
fromBool :: Num a => Bool -> a
toBool :: Num a => a -> Bool
maybeNew :: (a -> IO (Ptr a)) -> Maybe a -> IO (Ptr a)
maybeWith :: (a -> (Ptr b -> IO c) -> IO c) -> Maybe a -> (Ptr b -> IO c) -> IO c
maybePeek :: (Ptr a -> IO b) -> Ptr a -> IO (Maybe b)
withMany :: (a -> (b -> res) -> res) -> [a] -> ([b] -> res) -> res
copyBytes :: Ptr a -> Ptr a -> Int -> IO ()
moveBytes :: Ptr a -> Ptr a -> Int -> IO ()

General marshalling utilities
Combined allocation and marshalling
with :: Storable a => a -> (Ptr a -> IO b) -> IO b
``with` val f` executes the computation `f`, passing as argument a pointer to a temporarily allocated block of memory into which `val` has been marshalled (the combination of `alloca` and `poke`). The memory is freed when `f` terminates (either normally or via an exception), so the pointer passed to `f` must not be used after this.
new :: Storable a => a -> IO (Ptr a)
Allocate a block of memory and marshal a value into it (the combination of `malloc` and `poke`). The size of the area allocated is determined by the `sizeOf` method from the instance of `Storable` for the appropriate type. The memory may be deallocated using `free` or `finalizerFree` when no longer required.
Marshalling of Boolean values (non-zero corresponds to `True`)
fromBool :: Num a => Bool -> a
Convert a Haskell `Bool` to its numeric representation
toBool :: Num a => a -> Bool
Convert a Boolean in numeric representation to a Haskell value
Marshalling of Maybe values
maybeNew :: (a -> IO (Ptr a)) -> Maybe a -> IO (Ptr a)

Allocate storage and marshall a storable value wrapped into a `Maybe`

- the `nullPtr` is used to represent `Nothing`

maybeWith :: (a -> (Ptr b -> IO c) -> IO c) -> Maybe a -> (Ptr b -> IO c) -> IO c
Converts a `withXXX` combinator into one marshalling a value wrapped into a `Maybe`, using `nullPtr` to represent `Nothing`.
maybePeek :: (Ptr a -> IO b) -> Ptr a -> IO (Maybe b)
Convert a peek combinator into a one returning `Nothing` if applied to a `nullPtr`
Marshalling lists of storable objects
withMany :: (a -> (b -> res) -> res) -> [a] -> ([b] -> res) -> res
Replicates a `withXXX` combinator over a list of objects, yielding a list of marshalled objects
Haskellish interface to memcpy and memmove
(argument order: destination, source)
copyBytes :: Ptr a -> Ptr a -> Int -> IO ()
Copies the given number of bytes from the second area (source) into the first (destination); the copied areas may not overlap
moveBytes :: Ptr a -> Ptr a -> Int -> IO ()
Copies the given number of bytes from the second area (source) into the first (destination); the copied areas may overlap
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