Copyright | Will Thompson, Iñaki García Etxebarria and Jonas Platte |
---|---|
License | LGPL-2.1 |
Maintainer | Iñaki García Etxebarria (garetxe@gmail.com) |
Safe Haskell | None |
Language | Haskell2010 |
GCancellable is a thread-safe operation cancellation stack used throughout GIO to allow for cancellation of synchronous and asynchronous operations.
- newtype Cancellable = Cancellable (ManagedPtr Cancellable)
- class GObject o => IsCancellable o
- toCancellable :: IsCancellable o => o -> IO Cancellable
- noCancellable :: Maybe Cancellable
- data CancellableCancelMethodInfo
- cancellableCancel :: (HasCallStack, MonadIO m, IsCancellable a) => a -> m ()
- data CancellableConnectMethodInfo
- cancellableConnect :: (HasCallStack, MonadIO m, IsCancellable a) => a -> Callback -> m CULong
- data CancellableDisconnectMethodInfo
- cancellableDisconnect :: (HasCallStack, MonadIO m, IsCancellable a) => a -> CULong -> m ()
- cancellableGetCurrent :: (HasCallStack, MonadIO m) => m (Maybe Cancellable)
- data CancellableGetFdMethodInfo
- cancellableGetFd :: (HasCallStack, MonadIO m, IsCancellable a) => a -> m Int32
- data CancellableIsCancelledMethodInfo
- cancellableIsCancelled :: (HasCallStack, MonadIO m, IsCancellable a) => a -> m Bool
- data CancellableMakePollfdMethodInfo
- cancellableMakePollfd :: (HasCallStack, MonadIO m, IsCancellable a) => a -> PollFD -> m Bool
- cancellableNew :: (HasCallStack, MonadIO m) => m Cancellable
- data CancellablePopCurrentMethodInfo
- cancellablePopCurrent :: (HasCallStack, MonadIO m, IsCancellable a) => a -> m ()
- data CancellablePushCurrentMethodInfo
- cancellablePushCurrent :: (HasCallStack, MonadIO m, IsCancellable a) => a -> m ()
- data CancellableReleaseFdMethodInfo
- cancellableReleaseFd :: (HasCallStack, MonadIO m, IsCancellable a) => a -> m ()
- data CancellableResetMethodInfo
- cancellableReset :: (HasCallStack, MonadIO m, IsCancellable a) => a -> m ()
- data CancellableSetErrorIfCancelledMethodInfo
- cancellableSetErrorIfCancelled :: (HasCallStack, MonadIO m, IsCancellable a) => a -> m ()
- type C_CancellableCancelledCallback = Ptr () -> Ptr () -> IO ()
- type CancellableCancelledCallback = IO ()
- data CancellableCancelledSignalInfo
- afterCancellableCancelled :: (IsCancellable a, MonadIO m) => a -> CancellableCancelledCallback -> m SignalHandlerId
- genClosure_CancellableCancelled :: CancellableCancelledCallback -> IO Closure
- mk_CancellableCancelledCallback :: C_CancellableCancelledCallback -> IO (FunPtr C_CancellableCancelledCallback)
- noCancellableCancelledCallback :: Maybe CancellableCancelledCallback
- onCancellableCancelled :: (IsCancellable a, MonadIO m) => a -> CancellableCancelledCallback -> m SignalHandlerId
- wrap_CancellableCancelledCallback :: CancellableCancelledCallback -> Ptr () -> Ptr () -> IO ()
Exported types
newtype Cancellable Source #
GObject Cancellable Source # | |
IsObject Cancellable Source # | |
IsCancellable Cancellable Source # | |
((~) * info (ResolveCancellableMethod t Cancellable), MethodInfo * info Cancellable p) => IsLabel t (Cancellable -> p) Source # | |
((~) * info (ResolveCancellableMethod t Cancellable), MethodInfo * info Cancellable p) => IsLabelProxy t (Cancellable -> p) Source # | |
HasAttributeList * Cancellable Source # | |
type AttributeList Cancellable Source # | |
type SignalList Cancellable Source # | |
class GObject o => IsCancellable o Source #
toCancellable :: IsCancellable o => o -> IO Cancellable Source #
Methods
cancel
data CancellableCancelMethodInfo Source #
((~) * signature (m ()), MonadIO m, IsCancellable a) => MethodInfo * CancellableCancelMethodInfo a signature Source # | |
:: (HasCallStack, MonadIO m, IsCancellable a) | |
=> a |
|
-> m () |
Will set cancellable
to cancelled, and will emit the
Cancellable
::cancelled
signal. (However, see the warning about
race conditions in the documentation for that signal if you are
planning to connect to it.)
This function is thread-safe. In other words, you can safely call
it from a thread other than the one running the operation that was
passed the cancellable
.
If cancellable
is Nothing
, this function returns immediately for convenience.
The convention within GIO is that cancelling an asynchronous
operation causes it to complete asynchronously. That is, if you
cancel the operation from the same thread in which it is running,
then the operation's AsyncReadyCallback
will not be invoked until
the application returns to the main loop.
connect
data CancellableConnectMethodInfo Source #
((~) * signature (Callback -> m CULong), MonadIO m, IsCancellable a) => MethodInfo * CancellableConnectMethodInfo a signature Source # | |
:: (HasCallStack, MonadIO m, IsCancellable a) | |
=> a |
|
-> Callback |
|
-> m CULong | Returns: The id of the signal handler or 0 if |
Convenience function to connect to the Cancellable
::cancelled
signal. Also handles the race condition that may happen
if the cancellable is cancelled right before connecting.
callback
is called at most once, either directly at the
time of the connect if cancellable
is already cancelled,
or when cancellable
is cancelled in some thread.
dataDestroyFunc
will be called when the handler is
disconnected, or immediately if the cancellable is already
cancelled.
See Cancellable
::cancelled
for details on how to use this.
Since GLib 2.40, the lock protecting cancellable
is not held when
callback
is invoked. This lifts a restriction in place for
earlier GLib versions which now makes it easier to write cleanup
code that unconditionally invokes e.g. cancellableCancel
.
Since: 2.22
disconnect
data CancellableDisconnectMethodInfo Source #
((~) * signature (CULong -> m ()), MonadIO m, IsCancellable a) => MethodInfo * CancellableDisconnectMethodInfo a signature Source # | |
cancellableDisconnect Source #
:: (HasCallStack, MonadIO m, IsCancellable a) | |
=> a |
|
-> CULong |
|
-> m () |
Disconnects a handler from a cancellable instance similar to
signalHandlerDisconnect
. Additionally, in the event that a
signal handler is currently running, this call will block until the
handler has finished. Calling this function from a
Cancellable
::cancelled
signal handler will therefore result in a
deadlock.
This avoids a race condition where a thread cancels at the
same time as the cancellable operation is finished and the
signal handler is removed. See Cancellable
::cancelled
for
details on how to use this.
If cancellable
is Nothing
or handlerId
is 0
this function does
nothing.
Since: 2.22
getCurrent
cancellableGetCurrent Source #
:: (HasCallStack, MonadIO m) | |
=> m (Maybe Cancellable) | Returns: a |
Gets the top cancellable from the stack.
getFd
data CancellableGetFdMethodInfo Source #
((~) * signature (m Int32), MonadIO m, IsCancellable a) => MethodInfo * CancellableGetFdMethodInfo a signature Source # | |
:: (HasCallStack, MonadIO m, IsCancellable a) | |
=> a |
|
-> m Int32 | Returns: A valid file descriptor. %-1 if the file descriptor is not supported, or on errors. |
Gets the file descriptor for a cancellable job. This can be used to
implement cancellable operations on Unix systems. The returned fd will
turn readable when cancellable
is cancelled.
You are not supposed to read from the fd yourself, just check for
readable status. Reading to unset the readable status is done
with cancellableReset
.
After a successful return from this function, you should use
cancellableReleaseFd
to free up resources allocated for
the returned file descriptor.
See also cancellableMakePollfd
.
isCancelled
data CancellableIsCancelledMethodInfo Source #
((~) * signature (m Bool), MonadIO m, IsCancellable a) => MethodInfo * CancellableIsCancelledMethodInfo a signature Source # | |
cancellableIsCancelled Source #
:: (HasCallStack, MonadIO m, IsCancellable a) | |
=> a |
|
-> m Bool | Returns: |
Checks if a cancellable job has been cancelled.
makePollfd
data CancellableMakePollfdMethodInfo Source #
((~) * signature (PollFD -> m Bool), MonadIO m, IsCancellable a) => MethodInfo * CancellableMakePollfdMethodInfo a signature Source # | |
cancellableMakePollfd Source #
:: (HasCallStack, MonadIO m, IsCancellable a) | |
=> a |
|
-> PollFD |
|
-> m Bool | Returns: |
Creates a PollFD
corresponding to cancellable
; this can be passed
to poll
and used to poll for cancellation. This is useful both
for unix systems without a native poll and for portability to
windows.
When this function returns True
, you should use
cancellableReleaseFd
to free up resources allocated for the
pollfd
. After a False
return, do not call cancellableReleaseFd
.
If this function returns False
, either no cancellable
was given or
resource limits prevent this function from allocating the necessary
structures for polling. (On Linux, you will likely have reached
the maximum number of file descriptors.) The suggested way to handle
these cases is to ignore the cancellable
.
You are not supposed to read from the fd yourself, just check for
readable status. Reading to unset the readable status is done
with cancellableReset
.
Since: 2.22
new
:: (HasCallStack, MonadIO m) | |
=> m Cancellable | Returns: a |
Creates a new Cancellable
object.
Applications that want to start one or more operations
that should be cancellable should create a Cancellable
and pass it to the operations.
One Cancellable
can be used in multiple consecutive
operations or in multiple concurrent operations.
popCurrent
data CancellablePopCurrentMethodInfo Source #
((~) * signature (m ()), MonadIO m, IsCancellable a) => MethodInfo * CancellablePopCurrentMethodInfo a signature Source # | |
cancellablePopCurrent Source #
:: (HasCallStack, MonadIO m, IsCancellable a) | |
=> a |
|
-> m () |
Pops cancellable
off the cancellable stack (verifying that cancellable
is on the top of the stack).
pushCurrent
data CancellablePushCurrentMethodInfo Source #
((~) * signature (m ()), MonadIO m, IsCancellable a) => MethodInfo * CancellablePushCurrentMethodInfo a signature Source # | |
cancellablePushCurrent Source #
:: (HasCallStack, MonadIO m, IsCancellable a) | |
=> a |
|
-> m () |
Pushes cancellable
onto the cancellable stack. The current
cancellable can then be received using cancellableGetCurrent
.
This is useful when implementing cancellable operations in code that does not allow you to pass down the cancellable object.
This is typically called automatically by e.g. File
operations,
so you rarely have to call this yourself.
releaseFd
data CancellableReleaseFdMethodInfo Source #
((~) * signature (m ()), MonadIO m, IsCancellable a) => MethodInfo * CancellableReleaseFdMethodInfo a signature Source # | |
:: (HasCallStack, MonadIO m, IsCancellable a) | |
=> a |
|
-> m () |
Releases a resources previously allocated by cancellableGetFd
or cancellableMakePollfd
.
For compatibility reasons with older releases, calling this function
is not strictly required, the resources will be automatically freed
when the cancellable
is finalized. However, the cancellable
will
block scarce file descriptors until it is finalized if this function
is not called. This can cause the application to run out of file
descriptors when many GCancellables
are used at the same time.
Since: 2.22
reset
data CancellableResetMethodInfo Source #
((~) * signature (m ()), MonadIO m, IsCancellable a) => MethodInfo * CancellableResetMethodInfo a signature Source # | |
:: (HasCallStack, MonadIO m, IsCancellable a) | |
=> a |
|
-> m () |
Resets cancellable
to its uncancelled state.
If cancellable is currently in use by any cancellable operation then the behavior of this function is undefined.
Note that it is generally not a good idea to reuse an existing cancellable for more operations after it has been cancelled once, as this function might tempt you to do. The recommended practice is to drop the reference to a cancellable after cancelling it, and let it die with the outstanding async operations. You should create a fresh cancellable for further async operations.
setErrorIfCancelled
data CancellableSetErrorIfCancelledMethodInfo Source #
((~) * signature (m ()), MonadIO m, IsCancellable a) => MethodInfo * CancellableSetErrorIfCancelledMethodInfo a signature Source # | |
cancellableSetErrorIfCancelled Source #
:: (HasCallStack, MonadIO m, IsCancellable a) | |
=> a |
|
-> m () | (Can throw |
If the cancellable
is cancelled, sets the error to notify
that the operation was cancelled.
Signals
cancelled
type CancellableCancelledCallback = IO () Source #
afterCancellableCancelled :: (IsCancellable a, MonadIO m) => a -> CancellableCancelledCallback -> m SignalHandlerId Source #
mk_CancellableCancelledCallback :: C_CancellableCancelledCallback -> IO (FunPtr C_CancellableCancelledCallback) Source #
onCancellableCancelled :: (IsCancellable a, MonadIO m) => a -> CancellableCancelledCallback -> m SignalHandlerId Source #
wrap_CancellableCancelledCallback :: CancellableCancelledCallback -> Ptr () -> Ptr () -> IO () Source #