Safe Haskell | None |
---|---|

Language | Haskell98 |

We wrap most objects in a "managed pointer", which is basically a
`ForeignPtr`

of the appropriate type together with a notion of
"disowning", which means not running the finalizers passed upon
construction of the object upon garbage collection. The routines in
this module deal with the memory management of such managed
pointers.

## Synopsis

- newManagedPtr :: Ptr a -> IO () -> IO (ManagedPtr a)
- newManagedPtr' :: FinalizerPtr a -> Ptr a -> IO (ManagedPtr a)
- withManagedPtr :: (HasCallStack, ManagedPtrNewtype a) => a -> (Ptr a -> IO c) -> IO c
- maybeWithManagedPtr :: (HasCallStack, ManagedPtrNewtype a) => Maybe a -> (Ptr a -> IO c) -> IO c
- withManagedPtrList :: (HasCallStack, ManagedPtrNewtype a) => [a] -> ([Ptr a] -> IO c) -> IO c
- withTransient :: (HasCallStack, ManagedPtrNewtype a) => (ManagedPtr a -> a) -> Ptr a -> (a -> IO b) -> IO b
- unsafeManagedPtrGetPtr :: (HasCallStack, ManagedPtrNewtype a) => a -> IO (Ptr a)
- unsafeManagedPtrCastPtr :: forall a b. (HasCallStack, ManagedPtrNewtype a) => a -> IO (Ptr b)
- touchManagedPtr :: forall a. ManagedPtrNewtype a => a -> IO ()
- disownManagedPtr :: forall a. (HasCallStack, ManagedPtrNewtype a) => a -> IO (Ptr a)
- castTo :: forall o o'. (GObject o, GObject o') => (ManagedPtr o' -> o') -> o -> IO (Maybe o')
- unsafeCastTo :: forall o o'. (HasCallStack, GObject o, GObject o') => (ManagedPtr o' -> o') -> o -> IO o'
- newObject :: (HasCallStack, GObject a, GObject b) => (ManagedPtr a -> a) -> Ptr b -> IO a
- wrapObject :: forall a b. (HasCallStack, GObject a, GObject b) => (ManagedPtr a -> a) -> Ptr b -> IO a
- unrefObject :: GObject a => a -> IO ()
- disownObject :: GObject a => a -> IO (Ptr b)
- newBoxed :: forall a. BoxedObject a => (ManagedPtr a -> a) -> Ptr a -> IO a
- wrapBoxed :: forall a. BoxedObject a => (ManagedPtr a -> a) -> Ptr a -> IO a
- copyBoxed :: forall a. BoxedObject a => a -> IO (Ptr a)
- copyBoxedPtr :: forall a. BoxedObject a => Ptr a -> IO (Ptr a)
- freeBoxed :: forall a. (HasCallStack, BoxedObject a) => a -> IO ()
- disownBoxed :: (HasCallStack, BoxedObject a) => a -> IO (Ptr a)
- wrapPtr :: WrappedPtr a => (ManagedPtr a -> a) -> Ptr a -> IO a
- newPtr :: WrappedPtr a => (ManagedPtr a -> a) -> Ptr a -> IO a
- copyBytes :: WrappedPtr a => Int -> Ptr a -> IO (Ptr a)

# Managed pointers

newManagedPtr :: Ptr a -> IO () -> IO (ManagedPtr a) Source #

Thin wrapper over `newForeignPtr`

.

newManagedPtr' :: FinalizerPtr a -> Ptr a -> IO (ManagedPtr a) Source #

Version of `newManagedPtr`

taking a `FinalizerPtr`

and a
corresponding `Ptr`

, as in `newForeignPtr`

.

withManagedPtr :: (HasCallStack, ManagedPtrNewtype a) => a -> (Ptr a -> IO c) -> IO c Source #

Perform an IO action on the `Ptr`

inside a managed pointer.

maybeWithManagedPtr :: (HasCallStack, ManagedPtrNewtype a) => Maybe a -> (Ptr a -> IO c) -> IO c Source #

Like `withManagedPtr`

, but accepts a `Maybe`

type. If the passed
value is `Nothing`

the inner action will be executed with a
`nullPtr`

argument.

withManagedPtrList :: (HasCallStack, ManagedPtrNewtype a) => [a] -> ([Ptr a] -> IO c) -> IO c Source #

Perform an IO action taking a list of `Ptr`

on a list of managed
pointers.

withTransient :: (HasCallStack, ManagedPtrNewtype a) => (ManagedPtr a -> a) -> Ptr a -> (a -> IO b) -> IO b Source #

Perform the IO action with a transient managed pointer. The managed pointer will be valid while calling the action, but will be disowned as soon as the action finished.

unsafeManagedPtrGetPtr :: (HasCallStack, ManagedPtrNewtype a) => a -> IO (Ptr a) Source #

Return the `Ptr`

in a given managed pointer. As the name says,
this is potentially unsafe: the given `Ptr`

may only be used
*before* a call to `touchManagedPtr`

. This function is of most
interest to the autogenerated bindings, for hand-written code
`withManagedPtr`

is almost always a better choice.

unsafeManagedPtrCastPtr :: forall a b. (HasCallStack, ManagedPtrNewtype a) => a -> IO (Ptr b) Source #

Same as `unsafeManagedPtrGetPtr`

, but is polymorphic on the
return type.

touchManagedPtr :: forall a. ManagedPtrNewtype a => a -> IO () Source #

Ensure that the `Ptr`

in the given managed pointer is still alive
(i.e. it has not been garbage collected by the runtime) at the
point that this is called.

disownManagedPtr :: forall a. (HasCallStack, ManagedPtrNewtype a) => a -> IO (Ptr a) Source #

Do not run the finalizers upon garbage collection of the
`ManagedPtr`

.

# Safe casting

castTo :: forall o o'. (GObject o, GObject o') => (ManagedPtr o' -> o') -> o -> IO (Maybe o') Source #

Cast to the given type, checking that the cast is valid. If it is
not, we return `Nothing`

. Usage:

maybeWidget <- castTo Widget label

unsafeCastTo :: forall o o'. (HasCallStack, GObject o, GObject o') => (ManagedPtr o' -> o') -> o -> IO o' Source #

Cast to the given type, assuming that the cast will succeed. This
function will call `error`

if the cast is illegal.

# Wrappers

newObject :: (HasCallStack, GObject a, GObject b) => (ManagedPtr a -> a) -> Ptr b -> IO a Source #

Construct a Haskell wrapper for a `GObject`

, increasing its
reference count, or taking ownership of the floating reference if
there is one.

wrapObject :: forall a b. (HasCallStack, GObject a, GObject b) => (ManagedPtr a -> a) -> Ptr b -> IO a Source #

Same as `newObject`

, but we steal ownership of the object.

unrefObject :: GObject a => a -> IO () Source #

Decrease the reference count of the given `GObject`

. The memory
associated with the object may be released if the reference count
reaches 0.

disownObject :: GObject a => a -> IO (Ptr b) Source #

Disown a GObject, that is, do not unref the associated foreign GObject when the Haskell object gets garbage collected. Returns the pointer to the underlying GObject.

newBoxed :: forall a. BoxedObject a => (ManagedPtr a -> a) -> Ptr a -> IO a Source #

Construct a Haskell wrapper for the given boxed object. We make a copy of the object.

wrapBoxed :: forall a. BoxedObject a => (ManagedPtr a -> a) -> Ptr a -> IO a Source #

Like `newBoxed`

, but we do not make a copy (we "steal" the passed
object, so now it is managed by the Haskell runtime).

copyBoxed :: forall a. BoxedObject a => a -> IO (Ptr a) Source #

Make a copy of the given boxed object.

copyBoxedPtr :: forall a. BoxedObject a => Ptr a -> IO (Ptr a) Source #

Like `copyBoxed`

, but acting directly on a pointer, instead of a
managed pointer.

freeBoxed :: forall a. (HasCallStack, BoxedObject a) => a -> IO () Source #

Free the memory associated with a boxed object. Note that this
disowns the associated `ManagedPtr`

via `disownManagedPtr`

.

disownBoxed :: (HasCallStack, BoxedObject a) => a -> IO (Ptr a) Source #

Disown a boxed object, that is, do not free the associated
foreign GBoxed when the Haskell object gets garbage
collected. Returns the pointer to the underlying `BoxedObject`

.

wrapPtr :: WrappedPtr a => (ManagedPtr a -> a) -> Ptr a -> IO a Source #

Wrap a pointer, taking ownership of it.

newPtr :: WrappedPtr a => (ManagedPtr a -> a) -> Ptr a -> IO a Source #

Wrap a pointer, making a copy of the data.