[14:7] extends: object
GCancellable allows operations to be cancelled. GCancellable is a
thread-safe operation cancellation stack used throughout GIO to allow for
cancellation of synchronous and asynchronous operations.
Cancellable ()
Creates a new #GCancellable object. Applications that want to start one or more operations that should be cancellable should create a #GCancellable and pass it to the operations. One #GCancellable can be used in multiple consecutive operations or in multiple concurrent operations.
toNativeHandle (Source)
Normalizes a constructor argument into a raw pointer carrier. Accepts a raw NativeHandle, a raw NativeBuffer returned from
fn.call(...), another generated wrapper exposinghandle(), or null. Returns null when the argument carries no pointer.
Source is the raw handle, raw buffer, wrapper, or null.A raw pointer carrier or null when no pointer is present.getLib ()
Returns the opened native library for this generated wrapper.
The opened native library.handle ()
Returns the wrapped NativeHandle.
The wrapped NativeHandle.isNull ()
Returns true when the wrapped handle is null.
A bool.describe ()
Returns a small string for debugging generated wrappers.
A string.asObject ()
Wraps this handle as
Object.
A Object object.connectSignal (string Name, CallbackObj)
Connects one generated callback wrapper to a named signal.
Name is the signal name.CallbackObj is the generated callback wrapper to connect.The connected handler id.disconnectSignalHandler (int HandlerId)
Disconnects one retained signal handler id.
HandlerId is the signal handler id to disconnect.None.setOnCancelled (callback Fn, UserData = null)
Emitted when the operation has been cancelled. Can be used by implementations of cancellable operations. If the operation is cancelled from another thread, the signal will be emitted in the thread that cancelled the operation, not the thread that is running the operation. Note that disconnecting from this signal (or any signal) in a multi-threaded program is prone to race conditions. For instance it is possible that a signal handler may be invoked even after a call to g_signal_handler_disconnect() for that handler has already returned. There is also a problem when cancellation happens right before connecting to the signal. If this happens the signal will unexpectedly not be emitted, and checking before connecting to the signal leaves a race condition where this is still happening. In order to make it safe and easy to connect handlers there are two helper functions: g_cancellable_connect() and g_cancellable_disconnect() which protect against problems like this. An example of how to us this: |[ // Make sure we don't do unnecessary work if already cancelled if (g_cancellable_set_error_if_cancelled (cancellable, error)) return; // Set up all the data needed to be able to handle cancellation // of the operation my_data = my_data_new (...); id = 0; if (cancellable) id = g_cancellable_connect (cancellable, G_CALLBACK (cancelled_handler) data, NULL); // cancellable operation here... g_cancellable_disconnect (cancellable, id); // cancelled_handler is never called after this, it is now safe // to free the data my_data_free (my_data); ]| Note that the cancelled signal is emitted in the thread that the user cancelled from, which may be the main thread. So, the cancellable signal should not do something that can block.
Fn is the Aussom callback.Fn is called with (Cancellable Self).UserData is retained and passed through to the generated callback wrapper when provided.The connected handler id.cancel ()
Will set @cancellable to cancelled, and will emit the #GCancellable::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 %NULL, 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 #GAsyncReadyCallback will not be invoked until the application returns to the main loop. It is safe (although useless, since it will be a no-op) to call this function from a [signal@Gio.Cancellable::cancelled] signal handler.
None.disconnect (int handler_id)
Disconnects a handler from a cancellable instance similar to g_signal_handler_disconnect(). 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 #GCancellable::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 #GCancellable::cancelled for details on how to use this. If @cancellable is %NULL or @handler_id is
0this function does nothing.
handler_id is Handler id of the handler to be disconnected, or 0..None.get_fd ()
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 g_cancellable_reset(). After a successful return from this function, you should use g_cancellable_release_fd() to free up resources allocated for the returned file descriptor. See also g_cancellable_make_pollfd().
is_cancelled ()
Checks if a cancellable job has been cancelled.
make_pollfd (pollfd)
Creates a #GPollFD corresponding to @cancellable; this can be passed to g_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 g_cancellable_release_fd() to free up resources allocated for the @pollfd. After a %FALSE return, do not call g_cancellable_release_fd(). 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 g_cancellable_reset(). Note that in the event that a [signal@Gio.Cancellable::cancelled] signal handler is currently running, this call will block until the handler has finished. Calling this function from a signal handler will therefore result in a deadlock.
pollfd is a pointer to a #GPollFD.pop_current ()
Pops @cancellable off the cancellable stack (verifying that @cancellable is on the top of the stack).
None.push_current ()
Pushes @cancellable onto the cancellable stack. The current cancellable can then be received using g_cancellable_get_current(). 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. #GFile operations, so you rarely have to call this yourself.
None.release_fd ()
Releases a resources previously allocated by g_cancellable_get_fd() or g_cancellable_make_pollfd(). 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. Note that in the event that a [signal@Gio.Cancellable::cancelled] signal handler is currently running, this call will block until the handler has finished. Calling this function from a signal handler will therefore result in a deadlock.
None.reset ()
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. In the event that a [signal@Gio.Cancellable::cancelled] signal handler is currently running, this call will block until the handler has finished. Calling this function from a signal handler will therefore result in a deadlock.
None.set_error_if_cancelled ()
If the @cancellable is cancelled, sets the error to notify that the operation was cancelled.
source_new ()
Creates a source that triggers if @cancellable is cancelled and calls its callback of type #GCancellableSourceFunc. This is primarily useful for attaching to another (non-cancellable) source with g_source_add_child_source() to add cancellability to it. For convenience, you can call this with a %NULL #GCancellable, in which case the source will never trigger. The new #GSource will hold a reference to the #GCancellable.
[353:7] extends: object
Generated low-level callback wrapper for GIR callback cancelled.
CancellableCancelledCallback (callback Fn, UserData = null)
Creates one native callback wrapper. The wrapper owns a trampoline that converts native pointers into generated wrapper objects before invoking
Fn.
Fn is the Aussom callback implementation.UserData is retained and passed through to Fn on each invocation when provided.trampoline (nativeSelf, nativeUserData)
Internal trampoline. Converts native pointer arguments into generated wrapper instances, then invokes the user's callback.
callback ()
Returns the wrapped NativeCallback.
handle ()
Returns the callback as a NativeHandle.
close ()
Closes the underlying NativeCallback.
isClosed ()
Returns true when the callback has been closed.
[423:14] static extends: object
Generated metadata helpers for Cancellable class surfaces.
signals ()
Returns signal metadata for
Cancellable.
A list.
