Foreign.Ptr

base-4.9.0.0: Basic libraries

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 Ptr a
- 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
- nullFunPtr :: FunPtr a
- castFunPtr :: FunPtr a -> FunPtr b
- castFunPtrToPtr :: FunPtr a -> Ptr b
- castPtrToFunPtr :: Ptr a -> FunPtr b
- freeHaskellFunPtr :: FunPtr a -> IO ()
- data IntPtr
- ptrToIntPtr :: Ptr a -> IntPtr
- intPtrToPtr :: IntPtr -> Ptr a
- data WordPtr
- ptrToWordPtr :: Ptr a -> WordPtr
- wordPtrToPtr :: WordPtr -> Ptr a

# 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`