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use crate::{QBox, QObject, QPointerOfQObject};
use cpp_core::{
CastFrom, CastInto, CppBox, CppDeletable, DynamicCast, Ptr, Ref, StaticDowncast, StaticUpcast,
};
use std::fmt;
use std::ops::Deref;
/// A smart pointer that automatically sets to null when the object is deleted.
///
/// `QPtr` exposes functionality provided by the `QPointer<T>` C++ class.
/// `QPtr` can only contain a pointer to a `QObject`-based object. When that object is
/// deleted, `QPtr` automatically becomes a null pointer.
///
/// Note that dereferencing a null `QPtr` will panic, so if it's known that the object may
/// already have been deleted, you should use `is_null()`, `as_ref()`,
/// or a similar method to check
/// if the object is still alive before calling its methods.
///
/// `QPtr` is not an owning pointer, similar to `cpp_core::Ptr`. If you actually own the object,
/// you should convert it to `QBox` (it will delete the object when dropped if it has no parent)
/// or `CppBox` (it will always delete the object when dropped). `QPtr` provides `into_qbox` and
/// `to_box` helpers for that.
///
/// # Safety
///
/// While `QPtr` is much safer than `cpp_core::Ptr` and prevents use-after-free in common cases,
/// it is unsafe to use in Rust terms. `QPtr::new` must receive a valid pointer or a null pointer,
/// otherwise the behavior is undefined. You should not store pointers of other types
/// (e.g. `Ptr`, `Ref`, or raw pointers) produced by `QPtr` because, unlike `QPtr`, these
/// pointers will not become null pointers when the object is deleted.
///
/// It's still possible to cause use-after-free by calling a method through `QPtr`.
/// Even in a single threaded program, the accessed object can be deleted by a nested call
/// while one of its methods is still running. In multithreaded context, the object can be deleted
/// in another thread between the null check and the method call, also resulting in undefined
/// behavior.
pub struct QPtr<T: StaticUpcast<QObject>> {
q_pointer: Option<CppBox<QPointerOfQObject>>,
target: Ptr<T>,
}
impl<T: StaticUpcast<QObject>> QPtr<T> {
/// Creates a `QPtr` from a `Ptr`.
///
/// ### Safety
///
/// `target` must be either a valid pointer to an object or a null pointer.
/// See type level documentation.
pub unsafe fn new(target: impl CastInto<Ptr<T>>) -> Self {
let target = target.cast_into();
QPtr {
q_pointer: if target.is_null() {
None
} else {
Some(QPointerOfQObject::new_1a(Ptr::from_raw(
target.as_raw_ptr(),
)))
},
target,
}
}
/// Creates a `QPtr` from a raw pointer.
///
/// ### Safety
///
/// `target` must be either a valid pointer to an object or a null pointer.
/// See type level documentation.
pub unsafe fn from_raw(target: *const T) -> Self {
Self::new(Ptr::from_raw(target))
}
/// Creates a null pointer.
///
/// Note that you can also use `NullPtr` to specify a null pointer to a function accepting
/// `impl CastInto<Ptr<_>>`. Unlike `Ptr`, `NullPtr` is not a generic type, so it will
/// not cause type inference issues.
///
/// Note that accessing the content of a null `QPtr` through `Deref` will result
/// in a panic.
///
/// ### Safety
///
/// Null pointers must not be dereferenced. See type level documentation.
pub unsafe fn null() -> Self {
Self::new(Ptr::<T>::null())
}
/// Returns true if the pointer is null.
///
/// ### Safety
///
/// See type level documentation.
pub unsafe fn is_null(&self) -> bool {
self.q_pointer.as_ref().map_or(true, |p| p.is_null())
}
/// Returns the content as a const `Ptr`.
///
/// ### Safety
///
/// See type level documentation.
pub unsafe fn as_ptr(&self) -> Ptr<T> {
if self.is_null() {
Ptr::null()
} else {
self.target
}
}
/// Returns the content as a raw const pointer.
///
/// ### Safety
///
/// See type level documentation.
pub unsafe fn as_raw_ptr(&self) -> *const T {
self.as_ptr().as_raw_ptr()
}
/// Returns the content as a raw pointer.
///
/// ### Safety
///
/// See type level documentation.
pub unsafe fn as_mut_raw_ptr(&self) -> *mut T {
self.as_ptr().as_mut_raw_ptr()
}
/// Returns the content as a const `Ref`. Returns `None` if `self` is a null pointer.
///
/// ### Safety
///
/// See type level documentation.
pub unsafe fn as_ref(&self) -> Option<Ref<T>> {
self.as_ptr().as_ref()
}
/// Returns a reference to the value. Returns `None` if the pointer is null.
///
/// ### Safety
///
/// `self` must be valid.
/// The content must not be read or modified through other ways while the returned reference
/// exists.See type level documentation.
pub unsafe fn as_raw_ref<'a>(&self) -> Option<&'a T> {
self.as_ref().map(|r| r.as_raw_ref())
}
/// Returns a mutable reference to the value. Returns `None` if the pointer is null.
///
/// ### Safety
///
/// `self` must be valid.
/// The content must not be read or modified through other ways while the returned reference
/// exists.See type level documentation.
pub unsafe fn as_mut_raw_ref<'a>(&self) -> Option<&'a mut T> {
self.as_ref().map(|r| r.as_mut_raw_ref())
}
/// Converts the pointer to the base class type `U`.
///
/// ### Safety
///
/// This operation is safe as long as `self` is valid or null. See type level documentation.
pub unsafe fn static_upcast<U>(&self) -> QPtr<U>
where
T: StaticUpcast<U>,
U: StaticUpcast<QObject>,
{
QPtr::<U>::new(self.as_ptr().static_upcast::<U>())
}
/// Converts the pointer to the derived class type `U`.
///
/// It's recommended to use `dynamic_cast` instead because it performs a checked conversion.
///
/// ### Safety
///
/// This operation is safe as long as `self` is valid and it's type is `U` or inherits from `U`,
/// of if `self` is a null pointer. See type level documentation.
pub unsafe fn static_downcast<U>(&self) -> QPtr<U>
where
T: StaticDowncast<U>,
U: StaticUpcast<QObject>,
{
QPtr::<U>::new(self.as_ptr().static_downcast())
}
/// Converts the pointer to the derived class type `U`. Returns `None` if the object's type
/// is not `U` and doesn't inherit `U`.
///
/// ### Safety
///
/// This operation is safe as long as `self` is valid or null. See type level documentation.
pub unsafe fn dynamic_cast<U>(&self) -> QPtr<U>
where
T: DynamicCast<U>,
U: StaticUpcast<QObject>,
{
QPtr::<U>::new(self.as_ptr().dynamic_cast())
}
/// Converts this pointer to a `CppBox`. Returns `None` if `self`
/// is a null pointer.
///
/// Use this function to take ownership of the object. This is
/// the same as `CppBox::new`. `CppBox` will delete the object when dropped.
///
/// You can also use `into_qbox` to convert the pointer to a `QBox`.
/// Unlike `CppBox`, `QBox` will only delete the object if it has no parent.
///
/// ### Safety
///
/// `CppBox` will attempt to delete the object on drop. If something else also tries to
/// delete this object before or after that, the behavior is undefined.
/// See type level documentation.
pub unsafe fn to_box(&self) -> Option<CppBox<T>>
where
T: CppDeletable,
{
self.as_ptr().to_box()
}
/// Converts this pointer to a `QBox`.
///
/// Use this function to take ownership of the object. This is
/// the same as `QBox::from_q_mut_ptr`.
///
/// ### Safety
///
/// See type level documentation.
pub unsafe fn into_q_box(self) -> QBox<T>
where
T: CppDeletable,
{
QBox::from_q_ptr(self)
}
}
/// Creates another pointer to the same object.
impl<T: StaticUpcast<QObject>> Clone for QPtr<T> {
fn clone(&self) -> Self {
unsafe { QPtr::<T>::new(self.as_ptr()) }
}
}
impl<T: StaticUpcast<QObject>> fmt::Debug for QPtr<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "QPtr({:?})", unsafe { self.as_raw_ptr() })
}
}
/// Allows to call member functions of `T` and its base classes directly on the pointer.
///
/// Panics if the pointer is null.
impl<T: StaticUpcast<QObject>> Deref for QPtr<T> {
type Target = T;
fn deref(&self) -> &T {
unsafe {
let ptr = self.as_raw_ptr();
if ptr.is_null() {
panic!("attempted to deref a null QPtr<T>");
}
&*ptr
}
}
}
impl<'a, T, U> CastFrom<&'a QPtr<U>> for Ptr<T>
where
U: StaticUpcast<T> + StaticUpcast<QObject>,
{
unsafe fn cast_from(value: &'a QPtr<U>) -> Self {
CastFrom::cast_from(value.as_ptr())
}
}
impl<T, U> CastFrom<QPtr<U>> for Ptr<T>
where
U: StaticUpcast<T> + StaticUpcast<QObject>,
{
unsafe fn cast_from(value: QPtr<U>) -> Self {
CastFrom::cast_from(value.as_ptr())
}
}