Struct qt_core::QSemaphoreReleaser
source · #[repr(C)]pub struct QSemaphoreReleaser { /* private fields */ }
Expand description
The QSemaphoreReleaser class provides exception-safe deferral of a QSemaphore::release() call.
C++ class: QSemaphoreReleaser
.
The QSemaphoreReleaser class provides exception-safe deferral of a QSemaphore::release() call.
QSemaphoreReleaser can be used wherever you would otherwise use QSemaphore::release(). Constructing a QSemaphoreReleaser defers the release() call on the semaphore until the QSemaphoreReleaser is destroyed (see RAII pattern).
You can use this to reliably release a semaphore to avoid dead-lock in the face of exceptions or early returns:
// … do something that may throw or return early sem.release();
If an early return is taken or an exception is thrown before the sem.release()
call is reached, the semaphore is not released, possibly preventing the thread waiting in the corresponding sem.acquire()
call from ever continuing execution.
When using RAII instead:
const QSemaphoreReleaser releaser(sem); // … do something that may throw or early return // implicitly calls sem.release() here and at every other return in between
this can no longer happen, because the compiler will make sure that the QSemaphoreReleaser destructor is always called, and therefore the semaphore is always released.
QSemaphoreReleaser is move-enabled and can therefore be returned from functions to transfer responsibility for releasing a semaphore out of a function or a scope:
{ // some scope QSemaphoreReleaser releaser; // does nothing // … if (someCondition) { releaser = QSemaphoreReleaser(sem); // … } // … } // conditionally calls sem.release(), depending on someCondition
A QSemaphoreReleaser can be canceled by a call to cancel(). A canceled semaphore releaser will no longer call QSemaphore::release() in its destructor.
Implementations§
source§impl QSemaphoreReleaser
impl QSemaphoreReleaser
sourcepub unsafe fn cancel(&self) -> Ptr<QSemaphore>
Available on cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.
pub unsafe fn cancel(&self) -> Ptr<QSemaphore>
cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.Cancels this QSemaphoreReleaser such that the destructor will no longer call semaphore()->release()
. Returns the value of semaphore() before this call. After this call, semaphore() will return nullptr
.
Calls C++ function: QSemaphore* QSemaphoreReleaser::cancel()
.
Cancels this QSemaphoreReleaser such that the destructor will no longer call semaphore()->release()
. Returns the value of semaphore() before this call. After this call, semaphore() will return nullptr
.
To enable again, assign a new QSemaphoreReleaser:
releaser.cancel(); // avoid releasing old semaphore() releaser = QSemaphoreReleaser(sem, 42); // now will call sem.release(42) when ‘releaser’ is destroyed
sourcepub unsafe fn new() -> CppBox<QSemaphoreReleaser>
Available on cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.
pub unsafe fn new() -> CppBox<QSemaphoreReleaser>
cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.Default constructor. Creates a QSemaphoreReleaser that does nothing.
Calls C++ function: [constructor] void QSemaphoreReleaser::QSemaphoreReleaser()
.
Default constructor. Creates a QSemaphoreReleaser that does nothing.
sourcepub unsafe fn from_q_semaphore_int(
sem: impl CastInto<Ref<QSemaphore>>,
n: c_int
) -> CppBox<QSemaphoreReleaser>
Available on cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.
pub unsafe fn from_q_semaphore_int( sem: impl CastInto<Ref<QSemaphore>>, n: c_int ) -> CppBox<QSemaphoreReleaser>
cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.Constructor. Stores the arguments and calls sem.release(n) in the destructor.
Calls C++ function: [constructor] void QSemaphoreReleaser::QSemaphoreReleaser(QSemaphore& sem, int n = …)
.
Constructor. Stores the arguments and calls sem.release(n) in the destructor.
sourcepub unsafe fn from_q_semaphore_int2(
sem: impl CastInto<Ptr<QSemaphore>>,
n: c_int
) -> CppBox<QSemaphoreReleaser>
Available on cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.
pub unsafe fn from_q_semaphore_int2( sem: impl CastInto<Ptr<QSemaphore>>, n: c_int ) -> CppBox<QSemaphoreReleaser>
cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.Constructor. Stores the arguments and calls sem->release(n) in the destructor.
Calls C++ function: [constructor] void QSemaphoreReleaser::QSemaphoreReleaser(QSemaphore* sem, int n = …)
.
Constructor. Stores the arguments and calls sem->release(n) in the destructor.
sourcepub unsafe fn from_q_semaphore(
sem: impl CastInto<Ref<QSemaphore>>
) -> CppBox<QSemaphoreReleaser>
Available on cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.
pub unsafe fn from_q_semaphore( sem: impl CastInto<Ref<QSemaphore>> ) -> CppBox<QSemaphoreReleaser>
cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.Constructor. Stores the arguments and calls sem.release(n) in the destructor.
Calls C++ function: [constructor] void QSemaphoreReleaser::QSemaphoreReleaser(QSemaphore& sem)
.
Constructor. Stores the arguments and calls sem.release(n) in the destructor.
sourcepub unsafe fn from_q_semaphore2(
sem: impl CastInto<Ptr<QSemaphore>>
) -> CppBox<QSemaphoreReleaser>
Available on cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.
pub unsafe fn from_q_semaphore2( sem: impl CastInto<Ptr<QSemaphore>> ) -> CppBox<QSemaphoreReleaser>
cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.Constructor. Stores the arguments and calls sem->release(n) in the destructor.
Calls C++ function: [constructor] void QSemaphoreReleaser::QSemaphoreReleaser(QSemaphore* sem)
.
Constructor. Stores the arguments and calls sem->release(n) in the destructor.
sourcepub unsafe fn semaphore(&self) -> Ptr<QSemaphore>
Available on cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.
pub unsafe fn semaphore(&self) -> Ptr<QSemaphore>
cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.Returns a pointer to the QSemaphore object provided to the constructor, or by the last move assignment, if any. Otherwise, returns nullptr
.
Calls C++ function: QSemaphore* QSemaphoreReleaser::semaphore() const
.
Returns a pointer to the QSemaphore object provided to the constructor, or by the last move assignment, if any. Otherwise, returns nullptr
.
sourcepub unsafe fn swap(&self, other: impl CastInto<Ref<QSemaphoreReleaser>>)
Available on cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.
pub unsafe fn swap(&self, other: impl CastInto<Ref<QSemaphoreReleaser>>)
cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.Exchanges the responsibilites of *this
and other.
Calls C++ function: void QSemaphoreReleaser::swap(QSemaphoreReleaser& other)
.
Exchanges the responsibilites of *this
and other.
Unlike move assignment, neither of the two objects ever releases its semaphore, if any, as a consequence of swapping.
Therefore this function is very fast and never fails.
Trait Implementations§
source§impl CppDeletable for QSemaphoreReleaser
Available on cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.
impl CppDeletable for QSemaphoreReleaser
cpp_lib_version="5.11.3"
or cpp_lib_version="5.12.2"
or cpp_lib_version="5.13.0"
or cpp_lib_version="5.14.0"
only.source§unsafe fn delete(&self)
unsafe fn delete(&self)
Unless canceled, calls QSemaphore::release() with the arguments provided to the constructor, or by the last move assignment.
Calls C++ function: [destructor] void QSemaphoreReleaser::~QSemaphoreReleaser()
.
Unless canceled, calls QSemaphore::release() with the arguments provided to the constructor, or by the last move assignment.