Copyright	(c) The FFI task force 2001
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	ffi@haskell.org
Stability	provisional
Portability	portable
Safe Haskell	Trustworthy
Language	Haskell2010

Foreign.Ptr

Contents

Data pointers
Function pointers
Integral types with lossless conversion to and from pointers

Description

This module provides typed pointers to foreign data. It is part of the Foreign Function Interface (FFI) and will normally be imported via the Foreign module.

Synopsis

Data pointers

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 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.

Instances

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

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 second to the first argument. We have

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

Function pointers

data FunPtr a #

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

Instances

Eq (FunPtr a) #
Methods (==) :: FunPtr a -> FunPtr a -> Bool Source # (/=) :: FunPtr a -> FunPtr a -> Bool Source #
Ord (FunPtr a) #
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) #
Methods showsPrec :: Int -> FunPtr a -> ShowS # show :: FunPtr a -> String # showList :: [FunPtr a] -> ShowS #
Storable (FunPtr a) #
Methods sizeOf :: FunPtr a -> Int # alignment :: FunPtr a -> Int # peekElemOff :: Ptr (FunPtr a) -> Int -> IO (FunPtr a) # pokeElemOff :: Ptr (FunPtr a) -> Int -> FunPtr a -> IO () # peekByteOff :: Ptr b -> Int -> IO (FunPtr a) # pokeByteOff :: Ptr b -> Int -> FunPtr a -> IO () # peek :: Ptr (FunPtr a) -> IO (FunPtr a) # poke :: Ptr (FunPtr a) -> FunPtr a -> IO () #

nullFunPtr :: FunPtr a #

The constant nullFunPtr contains a distinguished value of FunPtr 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.

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 #

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.

freeHaskellFunPtr :: FunPtr a -> IO () #

Release the storage associated with the given FunPtr, which must have been obtained from a wrapper stub. This should be called whenever the return value from a foreign import wrapper function is no longer required; otherwise, the storage it uses will leak.

Integral types with lossless conversion to and from pointers

data IntPtr #

A signed integral type that can be losslessly converted to and from Ptr. This type is also compatible with the C99 type intptr_t, and can be marshalled to and from that type safely.

Instances

Bounded IntPtr #
Methods minBound :: IntPtr # maxBound :: IntPtr #
Enum IntPtr #
Methods succ :: IntPtr -> IntPtr # pred :: IntPtr -> IntPtr # toEnum :: Int -> IntPtr # fromEnum :: IntPtr -> Int # enumFrom :: IntPtr -> [IntPtr] # enumFromThen :: IntPtr -> IntPtr -> [IntPtr] # enumFromTo :: IntPtr -> IntPtr -> [IntPtr] # enumFromThenTo :: IntPtr -> IntPtr -> IntPtr -> [IntPtr] #
Eq IntPtr #
Methods (==) :: IntPtr -> IntPtr -> Bool Source # (/=) :: IntPtr -> IntPtr -> Bool Source #
Integral IntPtr #
Methods quot :: IntPtr -> IntPtr -> IntPtr # rem :: IntPtr -> IntPtr -> IntPtr # div :: IntPtr -> IntPtr -> IntPtr # mod :: IntPtr -> IntPtr -> IntPtr # quotRem :: IntPtr -> IntPtr -> (IntPtr, IntPtr) # divMod :: IntPtr -> IntPtr -> (IntPtr, IntPtr) # toInteger :: IntPtr -> Integer #
Num IntPtr #
Methods (+) :: IntPtr -> IntPtr -> IntPtr # (-) :: IntPtr -> IntPtr -> IntPtr # (*) :: IntPtr -> IntPtr -> IntPtr # negate :: IntPtr -> IntPtr # abs :: IntPtr -> IntPtr # signum :: IntPtr -> IntPtr # fromInteger :: Integer -> IntPtr #
Ord IntPtr #
Methods compare :: IntPtr -> IntPtr -> Ordering Source # (<) :: IntPtr -> IntPtr -> Bool Source # (<=) :: IntPtr -> IntPtr -> Bool Source # (>) :: IntPtr -> IntPtr -> Bool Source # (>=) :: IntPtr -> IntPtr -> Bool Source # max :: IntPtr -> IntPtr -> IntPtr Source # min :: IntPtr -> IntPtr -> IntPtr Source #
Read IntPtr #
Methods readsPrec :: Int -> ReadS IntPtr # readList :: ReadS [IntPtr] # readPrec :: ReadPrec IntPtr # readListPrec :: ReadPrec [IntPtr] #
Real IntPtr #
Methods toRational :: IntPtr -> Rational #
Show IntPtr #
Methods showsPrec :: Int -> IntPtr -> ShowS # show :: IntPtr -> String # showList :: [IntPtr] -> ShowS #
FiniteBits IntPtr #
Methods finiteBitSize :: IntPtr -> Int # countLeadingZeros :: IntPtr -> Int # countTrailingZeros :: IntPtr -> Int #
Bits IntPtr #
Methods (.&.) :: IntPtr -> IntPtr -> IntPtr # (.\|.) :: IntPtr -> IntPtr -> IntPtr # xor :: IntPtr -> IntPtr -> IntPtr # complement :: IntPtr -> IntPtr # shift :: IntPtr -> Int -> IntPtr # rotate :: IntPtr -> Int -> IntPtr # zeroBits :: IntPtr # bit :: Int -> IntPtr # setBit :: IntPtr -> Int -> IntPtr # clearBit :: IntPtr -> Int -> IntPtr # complementBit :: IntPtr -> Int -> IntPtr # testBit :: IntPtr -> Int -> Bool # bitSizeMaybe :: IntPtr -> Maybe Int # bitSize :: IntPtr -> Int # isSigned :: IntPtr -> Bool # shiftL :: IntPtr -> Int -> IntPtr # unsafeShiftL :: IntPtr -> Int -> IntPtr # shiftR :: IntPtr -> Int -> IntPtr # unsafeShiftR :: IntPtr -> Int -> IntPtr # rotateL :: IntPtr -> Int -> IntPtr # rotateR :: IntPtr -> Int -> IntPtr # popCount :: IntPtr -> Int #
Storable IntPtr #
Methods sizeOf :: IntPtr -> Int # alignment :: IntPtr -> Int # peekElemOff :: Ptr IntPtr -> Int -> IO IntPtr # pokeElemOff :: Ptr IntPtr -> Int -> IntPtr -> IO () # peekByteOff :: Ptr b -> Int -> IO IntPtr # pokeByteOff :: Ptr b -> Int -> IntPtr -> IO () # peek :: Ptr IntPtr -> IO IntPtr # poke :: Ptr IntPtr -> IntPtr -> IO () #

ptrToIntPtr :: Ptr a -> IntPtr #

casts a Ptr to an IntPtr

intPtrToPtr :: IntPtr -> Ptr a #

casts an IntPtr to a Ptr

data WordPtr #

An unsigned integral type that can be losslessly converted to and from Ptr. This type is also compatible with the C99 type uintptr_t, and can be marshalled to and from that type safely.

Instances

Bounded WordPtr #
Methods minBound :: WordPtr # maxBound :: WordPtr #
Enum WordPtr #
Methods succ :: WordPtr -> WordPtr # pred :: WordPtr -> WordPtr # toEnum :: Int -> WordPtr # fromEnum :: WordPtr -> Int # enumFrom :: WordPtr -> [WordPtr] # enumFromThen :: WordPtr -> WordPtr -> [WordPtr] # enumFromTo :: WordPtr -> WordPtr -> [WordPtr] # enumFromThenTo :: WordPtr -> WordPtr -> WordPtr -> [WordPtr] #
Eq WordPtr #
Methods (==) :: WordPtr -> WordPtr -> Bool Source # (/=) :: WordPtr -> WordPtr -> Bool Source #
Integral WordPtr #
Methods quot :: WordPtr -> WordPtr -> WordPtr # rem :: WordPtr -> WordPtr -> WordPtr # div :: WordPtr -> WordPtr -> WordPtr # mod :: WordPtr -> WordPtr -> WordPtr # quotRem :: WordPtr -> WordPtr -> (WordPtr, WordPtr) # divMod :: WordPtr -> WordPtr -> (WordPtr, WordPtr) # toInteger :: WordPtr -> Integer #
Num WordPtr #
Methods (+) :: WordPtr -> WordPtr -> WordPtr # (-) :: WordPtr -> WordPtr -> WordPtr # (*) :: WordPtr -> WordPtr -> WordPtr # negate :: WordPtr -> WordPtr # abs :: WordPtr -> WordPtr # signum :: WordPtr -> WordPtr # fromInteger :: Integer -> WordPtr #
Ord WordPtr #
Methods compare :: WordPtr -> WordPtr -> Ordering Source # (<) :: WordPtr -> WordPtr -> Bool Source # (<=) :: WordPtr -> WordPtr -> Bool Source # (>) :: WordPtr -> WordPtr -> Bool Source # (>=) :: WordPtr -> WordPtr -> Bool Source # max :: WordPtr -> WordPtr -> WordPtr Source # min :: WordPtr -> WordPtr -> WordPtr Source #
Read WordPtr #
Methods readsPrec :: Int -> ReadS WordPtr # readList :: ReadS [WordPtr] # readPrec :: ReadPrec WordPtr # readListPrec :: ReadPrec [WordPtr] #
Real WordPtr #
Methods toRational :: WordPtr -> Rational #
Show WordPtr #
Methods showsPrec :: Int -> WordPtr -> ShowS # show :: WordPtr -> String # showList :: [WordPtr] -> ShowS #
FiniteBits WordPtr #
Methods finiteBitSize :: WordPtr -> Int # countLeadingZeros :: WordPtr -> Int # countTrailingZeros :: WordPtr -> Int #
Bits WordPtr #
Methods (.&.) :: WordPtr -> WordPtr -> WordPtr # (.\|.) :: WordPtr -> WordPtr -> WordPtr # xor :: WordPtr -> WordPtr -> WordPtr # complement :: WordPtr -> WordPtr # shift :: WordPtr -> Int -> WordPtr # rotate :: WordPtr -> Int -> WordPtr # zeroBits :: WordPtr # bit :: Int -> WordPtr # setBit :: WordPtr -> Int -> WordPtr # clearBit :: WordPtr -> Int -> WordPtr # complementBit :: WordPtr -> Int -> WordPtr # testBit :: WordPtr -> Int -> Bool # bitSizeMaybe :: WordPtr -> Maybe Int # bitSize :: WordPtr -> Int # isSigned :: WordPtr -> Bool # shiftL :: WordPtr -> Int -> WordPtr # unsafeShiftL :: WordPtr -> Int -> WordPtr # shiftR :: WordPtr -> Int -> WordPtr # unsafeShiftR :: WordPtr -> Int -> WordPtr # rotateL :: WordPtr -> Int -> WordPtr # rotateR :: WordPtr -> Int -> WordPtr # popCount :: WordPtr -> Int #
Storable WordPtr #
Methods sizeOf :: WordPtr -> Int # alignment :: WordPtr -> Int # peekElemOff :: Ptr WordPtr -> Int -> IO WordPtr # pokeElemOff :: Ptr WordPtr -> Int -> WordPtr -> IO () # peekByteOff :: Ptr b -> Int -> IO WordPtr # pokeByteOff :: Ptr b -> Int -> WordPtr -> IO () # peek :: Ptr WordPtr -> IO WordPtr # poke :: Ptr WordPtr -> WordPtr -> IO () #

ptrToWordPtr :: Ptr a -> WordPtr #

casts a Ptr to a WordPtr

wordPtrToPtr :: WordPtr -> Ptr a #

casts a WordPtr to a Ptr