Foreign.Ptr

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.

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

(/=) :: Ptr a -> Ptr a -> Bool

(Data a, Typeable * 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)

Ord (Ptr a)

Methods

compare :: Ptr a -> Ptr a -> Ordering

(<) :: Ptr a -> Ptr a -> Bool

(<=) :: Ptr a -> Ptr a -> Bool

(>) :: Ptr a -> Ptr a -> Bool

(>=) :: Ptr a -> Ptr a -> Bool

max :: Ptr a -> Ptr a -> Ptr a

min :: Ptr a -> Ptr a -> Ptr a

Show (Ptr a)

Methods

showsPrec :: Int -> Ptr a -> ShowS

show :: Ptr a -> String

showList :: [Ptr a] -> ShowS

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 ()

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

(/=) :: FunPtr a -> FunPtr a -> Bool

Ord (FunPtr a)

Methods

compare :: FunPtr a -> FunPtr a -> Ordering

(<) :: FunPtr a -> FunPtr a -> Bool

(<=) :: FunPtr a -> FunPtr a -> Bool

(>) :: FunPtr a -> FunPtr a -> Bool

(>=) :: FunPtr a -> FunPtr a -> Bool

max :: FunPtr a -> FunPtr a -> FunPtr a

min :: FunPtr a -> FunPtr a -> FunPtr a

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

(/=) :: IntPtr -> IntPtr -> Bool

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

(<) :: IntPtr -> IntPtr -> Bool

(<=) :: IntPtr -> IntPtr -> Bool

(>) :: IntPtr -> IntPtr -> Bool

(>=) :: IntPtr -> IntPtr -> Bool

max :: IntPtr -> IntPtr -> IntPtr

min :: IntPtr -> IntPtr -> IntPtr

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

(/=) :: WordPtr -> WordPtr -> Bool

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

(<) :: WordPtr -> WordPtr -> Bool

(<=) :: WordPtr -> WordPtr -> Bool

(>) :: WordPtr -> WordPtr -> Bool

(>=) :: WordPtr -> WordPtr -> Bool

max :: WordPtr -> WordPtr -> WordPtr

min :: WordPtr -> WordPtr -> WordPtr

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