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GHC.Ptr

Portability | non-portable (GHC Extensions)
Stability | internal
Maintainer | ffi@haskell.org

Description
The `Ptr` and `FunPtr` types and operations.
Synopsis

data Ptr a = Ptr Addr#
nullPtr :: Ptr a
castPtr :: Ptr a -> Ptr b
plusPtr :: Ptr a -> Int -> Ptr b
alignPtr :: Ptr a -> Int -> Ptr a
minusPtr :: Ptr a -> Ptr b -> Int
data FunPtr a = FunPtr Addr#
nullFunPtr :: FunPtr a
castFunPtr :: FunPtr a -> FunPtr b
castFunPtrToPtr :: FunPtr a -> Ptr b
castPtrToFunPtr :: Ptr a -> FunPtr b

Documentation
data Ptr a

A value of type ``Ptr` a` represents a pointer to an object, or an array of objects, which may be marshalled to or from Haskell values of type `a`. The type `a` will normally be an instance of class `Storable` which provides the marshalling operations.
Constructors

Ptr Addr# |

Instances

IArray UArray (Ptr a)
Ix ix => Eq (UArray ix (Ptr a))
Ix ix => Ord (UArray ix (Ptr a))
MArray (STUArray s) (Ptr a) (ST s)
IArray (IOToDiffArray IOUArray) (Ptr a)
MArray IOUArray (Ptr a) IO
Typeable a => Typeable (Ptr a)
Show (Ptr a)
Storable (Ptr a)
Eq (Ptr a)
Ord (Ptr a)

nullPtr :: Ptr a
The constant `nullPtr` contains a distinguished value of `Ptr` that is not associated with a valid memory location.
castPtr :: Ptr a -> Ptr b
The `castPtr` function casts a pointer from one type to another.
plusPtr :: Ptr a -> Int -> Ptr b
Advances the given address by the given offset in bytes.
alignPtr :: Ptr a -> Int -> Ptr a
Given an arbitrary address and an alignment constraint, `alignPtr` yields the next higher address that fulfills the alignment constraint. An alignment constraint `x` is fulfilled by any address divisible by `x`. This operation is idempotent.
minusPtr :: Ptr a -> Ptr b -> Int

Computes the offset required to get from the first to the second argument. We have

     p2 == p1 `plusPtr` (p2 `minusPtr` p1)

data FunPtr a

A value of type ``FunPtr` a` is a pointer to a piece of code. It may be the pointer to a C function or to a Haskell function created using `foreign export dynamic`. A `foreign export dynamic` should normally be declared to produce a `FunPtr` of the correct type. For example:

     type Compare = Int -> Int -> Bool
     foreign export dynamic mkCompare :: Compare -> IO (FunPtr Compare)

Constructors

FunPtr Addr# |

Instances

IArray UArray (FunPtr a)
Ix ix => Eq (UArray ix (FunPtr a))
Ix ix => Ord (UArray ix (FunPtr a))
MArray (STUArray s) (FunPtr a) (ST s)
IArray (IOToDiffArray IOUArray) (FunPtr a)
MArray IOUArray (FunPtr a) IO
Show (FunPtr a)
Storable (FunPtr a)
Eq (FunPtr a)
Ord (FunPtr a)

nullFunPtr :: FunPtr a
The constant `nullFunPtr` contains a distinguished value of `Ptr` that is not associated with a valid memory location
castFunPtr :: FunPtr a -> FunPtr b
Casts a `FunPtr` to a `FunPtr` of a different type
castFunPtrToPtr :: FunPtr a -> Ptr b
Casts a `FunPtr` to a `Ptr`
castPtrToFunPtr :: Ptr a -> FunPtr b
Casts a `Ptr` to a `FunPtr`
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