GHC.Ptr

base-4.14.0.0: Basic libraries

Copyright | (c) The FFI Task Force 2000-2002
License | see libraries/base/LICENSE
Maintainer | ffi@haskell.org
Stability | internal
Portability | non-portable (GHC Extensions)
Safe Haskell | Unsafe
Language | Haskell2010

GHC.Ptr

Contents

- Unsafe functions

Description

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

Synopsis

- data Ptr a = Ptr Addr#
- data FunPtr a = FunPtr 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
- nullFunPtr :: FunPtr a
- castFunPtr :: FunPtr a -> FunPtr b
- castFunPtrToPtr :: FunPtr a -> Ptr b
- castPtrToFunPtr :: Ptr a -> FunPtr b

# Documentation

data Ptr a Source #

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 often be an instance of class `Storable` which provides the marshalling operations. However this is not essential, and you can provide your own operations to access the pointer. For example you might write small foreign functions to get or set the fields of a C `struct`.

Constructors

Ptr Addr# |

#### Instances

Instances details

Generic1 (URec (Ptr ()) :: k -> Type) # | Since: base-4.9.0.0
Instance details Defined in GHC.Generics Associated Types type Rep1 (URec (Ptr ())) :: k -> Type Source # Methods from1 :: forall (a :: k0). URec (Ptr ()) a -> Rep1 (URec (Ptr ())) a Source # to1 :: forall (a :: k0). Rep1 (URec (Ptr ())) a -> URec (Ptr ()) a Source #
Eq (Ptr a) # | Since: base-2.1
Instance details Defined in GHC.Ptr Methods (==) :: Ptr a -> Ptr a -> Bool Source # (/=) :: Ptr a -> Ptr a -> Bool Source #
Data a => Data (Ptr a) # | Since: base-4.8.0.0
Instance details Defined in Data.Data Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Ptr a -> c (Ptr a) Source # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Ptr a) Source # toConstr :: Ptr a -> Constr Source # dataTypeOf :: Ptr a -> DataType Source # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Ptr a)) Source # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Ptr a)) Source # gmapT :: (forall b. Data b => b -> b) -> Ptr a -> Ptr a Source # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Ptr a -> r Source # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Ptr a -> r Source # gmapQ :: (forall d. Data d => d -> u) -> Ptr a -> [u] Source # gmapQi :: Int -> (forall d. Data d => d -> u) -> Ptr a -> u Source # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Ptr a -> m (Ptr a) Source # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Ptr a -> m (Ptr a) Source # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Ptr a -> m (Ptr a) Source #
Ord (Ptr a) # | Since: base-2.1
Instance details Defined in GHC.Ptr Methods compare :: Ptr a -> Ptr a -> Ordering Source # (<) :: Ptr a -> Ptr a -> Bool Source # (<=) :: Ptr a -> Ptr a -> Bool Source # (>) :: Ptr a -> Ptr a -> Bool Source # (>=) :: Ptr a -> Ptr a -> Bool Source # max :: Ptr a -> Ptr a -> Ptr a Source # min :: Ptr a -> Ptr a -> Ptr a Source #
Show (Ptr a) # | Since: base-2.1
Instance details Defined in GHC.Ptr Methods showsPrec :: Int -> Ptr a -> ShowS Source # show :: Ptr a -> String Source # showList :: [Ptr a] -> ShowS Source #
Foldable (UAddr :: Type -> Type) # | Since: base-4.9.0.0
Instance details Defined in Data.Foldable Methods fold :: Monoid m => UAddr m -> m Source # foldMap :: Monoid m => (a -> m) -> UAddr a -> m Source # foldMap' :: Monoid m => (a -> m) -> UAddr a -> m Source # foldr :: (a -> b -> b) -> b -> UAddr a -> b Source # foldr' :: (a -> b -> b) -> b -> UAddr a -> b Source # foldl :: (b -> a -> b) -> b -> UAddr a -> b Source # foldl' :: (b -> a -> b) -> b -> UAddr a -> b Source # foldr1 :: (a -> a -> a) -> UAddr a -> a Source # foldl1 :: (a -> a -> a) -> UAddr a -> a Source # toList :: UAddr a -> [a] Source # null :: UAddr a -> Bool Source # length :: UAddr a -> Int Source # elem :: Eq a => a -> UAddr a -> Bool Source # maximum :: Ord a => UAddr a -> a Source # minimum :: Ord a => UAddr a -> a Source # sum :: Num a => UAddr a -> a Source # product :: Num a => UAddr a -> a Source #
Traversable (UAddr :: Type -> Type) # | Since: base-4.9.0.0
Instance details Defined in Data.Traversable Methods traverse :: Applicative f => (a -> f b) -> UAddr a -> f (UAddr b) Source # sequenceA :: Applicative f => UAddr (f a) -> f (UAddr a) Source # mapM :: Monad m => (a -> m b) -> UAddr a -> m (UAddr b) Source # sequence :: Monad m => UAddr (m a) -> m (UAddr a) Source #
Storable (Ptr a) # | Since: base-2.1
Instance details Defined in Foreign.Storable Methods sizeOf :: Ptr a -> Int Source # alignment :: Ptr a -> Int Source # peekElemOff :: Ptr (Ptr a) -> Int -> IO (Ptr a) Source # pokeElemOff :: Ptr (Ptr a) -> Int -> Ptr a -> IO () Source # peekByteOff :: Ptr b -> Int -> IO (Ptr a) Source # pokeByteOff :: Ptr b -> Int -> Ptr a -> IO () Source # peek :: Ptr (Ptr a) -> IO (Ptr a) Source # poke :: Ptr (Ptr a) -> Ptr a -> IO () Source #
Functor (URec (Ptr ()) :: Type -> Type) # | Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods fmap :: (a -> b) -> URec (Ptr ()) a -> URec (Ptr ()) b Source # (<$) :: a -> URec (Ptr ()) b -> URec (Ptr ()) a Source #
Eq (URec (Ptr ()) p) # | Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods (==) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool Source # (/=) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool Source #
Ord (URec (Ptr ()) p) # | Since: base-4.9.0.0
Instance details Defined in GHC.Generics Methods compare :: URec (Ptr ()) p -> URec (Ptr ()) p -> Ordering Source # (<) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool Source # (<=) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool Source # (>) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool Source # (>=) :: URec (Ptr ()) p -> URec (Ptr ()) p -> Bool Source # max :: URec (Ptr ()) p -> URec (Ptr ()) p -> URec (Ptr ()) p Source # min :: URec (Ptr ()) p -> URec (Ptr ()) p -> URec (Ptr ()) p Source #
Generic (URec (Ptr ()) p) # | Since: base-4.9.0.0
Instance details Defined in GHC.Generics Associated Types type Rep (URec (Ptr ()) p) :: Type -> Type Source # Methods from :: URec (Ptr ()) p -> Rep (URec (Ptr ()) p) x Source # to :: Rep (URec (Ptr ()) p) x -> URec (Ptr ()) p Source #
data URec (Ptr ()) (p :: k) # | Used for marking occurrences of `Addr#` Since: base-4.9.0.0
Instance details Defined in GHC.Generics data URec (Ptr ()) (p :: k) = UAddr { uAddr# :: Addr# }
type Rep1 (URec (Ptr ()) :: k -> Type) # |
Instance details Defined in GHC.Generics type Rep1 (URec (Ptr ()) :: k -> Type) = D1 ('MetaData "URec" "GHC.Generics" "base" 'False) (C1 ('MetaCons "UAddr" 'PrefixI 'True) (S1 ('MetaSel ('Just "uAddr#") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (UAddr :: k -> Type)))
type Rep (URec (Ptr ()) p) # |
Instance details Defined in GHC.Generics type Rep (URec (Ptr ()) p) = D1 ('MetaData "URec" "GHC.Generics" "base" 'False) (C1 ('MetaCons "UAddr" 'PrefixI 'True) (S1 ('MetaSel ('Just "uAddr#") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (UAddr :: Type -> Type)))

data FunPtr a Source #

A value of type ``FunPtr` a` is a pointer to a function callable from foreign code. The type `a` will normally be a foreign type, a function type with zero or more arguments where

- the argument types are marshallable foreign types, i.e. `Char`, `Int`, `Double`, `Float`, `Bool`, `Int8`, `Int16`, `Int32`, `Int64`, `Word8`, `Word16`, `Word32`, `Word64`, ``Ptr` a`, ``FunPtr` a`, ``StablePtr` a` or a renaming of any of these using `newtype`.
- the return type is either a marshallable foreign type or has the form ``IO` t` where `t` is a marshallable foreign type or `()`.

A value of type ``FunPtr` a` may be a pointer to a foreign function, either returned by another foreign function or imported with a a static address import like

    foreign import ccall "stdlib.h &free"
      p_free :: FunPtr (Ptr a -> IO ())

or a pointer to a Haskell function created using a wrapper stub declared to produce a `FunPtr` of the correct type. For example:

    type Compare = Int -> Int -> Bool
    foreign import ccall "wrapper"
      mkCompare :: Compare -> IO (FunPtr Compare)

Calls to wrapper stubs like `mkCompare` allocate storage, which should be released with `freeHaskellFunPtr` when no longer required.

To convert `FunPtr` values to corresponding Haskell functions, one can define a dynamic stub for the specific foreign type, e.g.

    type IntFunction = CInt -> IO ()
    foreign import ccall "dynamic"
      mkFun :: FunPtr IntFunction -> IntFunction

Constructors

FunPtr Addr# |

#### Instances

Instances details

Eq (FunPtr a) # |
Instance details Defined in GHC.Ptr Methods (==) :: FunPtr a -> FunPtr a -> Bool Source # (/=) :: FunPtr a -> FunPtr a -> Bool Source #
Ord (FunPtr a) # |
Instance details Defined in GHC.Ptr Methods compare :: FunPtr a -> FunPtr a -> Ordering Source # (<) :: FunPtr a -> FunPtr a -> Bool Source # (<=) :: FunPtr a -> FunPtr a -> Bool Source # (>) :: FunPtr a -> FunPtr a -> Bool Source # (>=) :: FunPtr a -> FunPtr a -> Bool Source # max :: FunPtr a -> FunPtr a -> FunPtr a Source # min :: FunPtr a -> FunPtr a -> FunPtr a Source #
Show (FunPtr a) # | Since: base-2.1
Instance details Defined in GHC.Ptr Methods showsPrec :: Int -> FunPtr a -> ShowS Source # show :: FunPtr a -> String Source # showList :: [FunPtr a] -> ShowS Source #
Storable (FunPtr a) # | Since: base-2.1
Instance details Defined in Foreign.Storable Methods sizeOf :: FunPtr a -> Int Source # alignment :: FunPtr a -> Int Source # peekElemOff :: Ptr (FunPtr a) -> Int -> IO (FunPtr a) Source # pokeElemOff :: Ptr (FunPtr a) -> Int -> FunPtr a -> IO () Source # peekByteOff :: Ptr b -> Int -> IO (FunPtr a) Source # pokeByteOff :: Ptr b -> Int -> FunPtr a -> IO () Source # peek :: Ptr (FunPtr a) -> IO (FunPtr a) Source # poke :: Ptr (FunPtr a) -> FunPtr a -> IO () Source #

nullPtr :: Ptr a Source #

The constant `nullPtr` contains a distinguished value of `Ptr` that is not associated with a valid memory location.

castPtr :: Ptr a -> Ptr b Source #

The `castPtr` function casts a pointer from one type to another.

plusPtr :: Ptr a -> Int -> Ptr b Source #

Advances the given address by the given offset in bytes.

alignPtr :: Ptr a -> Int -> Ptr a Source #

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 Source #

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

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

nullFunPtr :: FunPtr a Source #

The constant `nullFunPtr` contains a distinguished value of `FunPtr` that is not associated with a valid memory location.

castFunPtr :: FunPtr a -> FunPtr b Source #

Casts a `FunPtr` to a `FunPtr` of a different type.

# Unsafe functions

castFunPtrToPtr :: FunPtr a -> Ptr b Source #

Casts a `FunPtr` to a `Ptr`.

Note: this is valid only on architectures where data and function pointers range over the same set of addresses, and should only be used for bindings to external libraries whose interface already relies on this assumption.

castPtrToFunPtr :: Ptr a -> FunPtr b Source #

Casts a `Ptr` to a `FunPtr`.

Note: this is valid only on architectures where data and function pointers range over the same set of addresses, and should only be used for bindings to external libraries whose interface already relies on this assumption.