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| Foreign.Ptr | | Portability | portable | | Stability | provisional | | Maintainer | ffi@haskell.org |
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| Contents |
- Data pointers
- Function pointers
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| Description |
| The Ptr 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.
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| Synopsis |
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| Data pointers |
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| 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. | | Instances | |
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| nullPtr :: Ptr a |
| The constant nullPtr contains a distinguished value of Ptr
that is not associated with a valid memory location. |
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| castPtr :: Ptr a -> Ptr b |
| The castPtr function casts a pointer from one type to another. |
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| plusPtr :: Ptr a -> Int -> Ptr b |
| Advances the given address by the given offset in bytes. |
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| 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. |
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| 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) |
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| Function pointers |
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| 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) | | Instances | |
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| nullFunPtr :: FunPtr a |
| The constant nullFunPtr contains a
distinguished value of Ptr that is not
associated with a valid memory location |
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| castFunPtr :: FunPtr a -> FunPtr b |
| Casts a FunPtr to a FunPtr of a different type |
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| castFunPtrToPtr :: FunPtr a -> Ptr b |
| Casts a FunPtr to a Ptr |
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| castPtrToFunPtr :: Ptr a -> FunPtr b |
| Casts a Ptr to a FunPtr |
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| freeHaskellFunPtr :: FunPtr a -> IO () |
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| Produced by Haddock version 0.4 |
