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Foreign.Marshal.Alloc

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

Contents

Memory allocation
  Local allocation
  Dynamic allocation

Description
Marshalling support: basic routines for memory allocation
Synopsis

alloca :: Storable a => (Ptr a -> IO b) -> IO b
allocaBytes :: Int -> (Ptr a -> IO b) -> IO b
malloc :: Storable a => IO (Ptr a)
mallocBytes :: Int -> IO (Ptr a)
realloc :: Storable b => Ptr a -> IO (Ptr b)
reallocBytes :: Ptr a -> Int -> IO (Ptr a)
free :: Ptr a -> IO ()
finalizerFree :: FinalizerPtr a

Memory allocation
Local allocation
alloca :: Storable a => (Ptr a -> IO b) -> IO b
``alloca` f` executes the computation `f`, passing as argument a pointer to a temporarily allocated block of memory sufficient to hold values of type `a`. 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.
allocaBytes :: Int -> (Ptr a -> IO b) -> IO b

``allocaBytes` n f` executes the computation `f`, passing as argument a pointer to a temporarily allocated block of memory of `n` bytes. The block of memory is sufficiently aligned for any of the basic foreign types that fits into a memory block of the allocated size.

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.

Dynamic allocation
malloc :: Storable a => IO (Ptr a)
Allocate a block of memory that is sufficient to hold values of type `a`. 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.
mallocBytes :: Int -> IO (Ptr a)
Allocate a block of memory of the given number of bytes. The block of memory is sufficiently aligned for any of the basic foreign types that fits into a memory block of the allocated size. The memory may be deallocated using `free` or `finalizerFree` when no longer required.
realloc :: Storable b => Ptr a -> IO (Ptr b)

Resize a memory area that was allocated with `malloc` or `mallocBytes` to the size needed to store values of type `b`. The returned pointer may refer to an entirely different memory area, but will be suitably aligned to hold values of type `b`. The contents of the referenced memory area will be the same as of the original pointer up to the minimum of the original size and the size of values of type `b`.

If the argument to `realloc` is `nullPtr`, `realloc` behaves like `malloc`.

reallocBytes :: Ptr a -> Int -> IO (Ptr a)

Resize a memory area that was allocated with `malloc` or `mallocBytes` to the given size. The returned pointer may refer to an entirely different memory area, but will be sufficiently aligned for any of the basic foreign types that fits into a memory block of the given size. The contents of the referenced memory area will be the same as of the original pointer up to the minimum of the original size and the given size.

If the pointer argument to `reallocBytes` is `nullPtr`, `reallocBytes` behaves like `malloc`. If the requested size is 0, `reallocBytes` behaves like `free`.

free :: Ptr a -> IO ()
Free a block of memory that was allocated with `malloc`, `mallocBytes`, `realloc`, `reallocBytes`, `new` or any of the `new` X functions in Foreign.Marshal.Array or Foreign.C.String.
finalizerFree :: FinalizerPtr a
A pointer to a foreign function equivalent to `free`, which may be used as a finalizer (cf `ForeignPtr`) for storage allocated with `malloc`, `mallocBytes`, `realloc` or `reallocBytes`.
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