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use super::*;
use core::any::Any;
use core::ffi::c_void;
use core::marker::PhantomData;
use core::mem::{forget, transmute_copy, MaybeUninit};
use core::ptr::NonNull;
/// Provides low-level access to an interface vtable.
///
/// This trait is automatically implemented by the generated bindings and should not be
/// implemented manually.
///
/// # Safety
pub unsafe trait Interface: Sized + Clone {
#[doc(hidden)]
type Vtable;
/// The `GUID` associated with the interface.
const IID: GUID;
#[doc(hidden)]
const UNKNOWN: bool = true;
/// A reference to the interface's vtable
#[doc(hidden)]
#[inline(always)]
fn vtable(&self) -> &Self::Vtable {
// SAFETY: the implementor of the trait guarantees that `Self` is castable to its vtable
unsafe { self.assume_vtable::<Self>() }
}
/// Cast this interface as a reference to the supplied interfaces `Vtable`
///
/// # Safety
///
/// This is safe if `T` is an equivalent interface to `Self` or a super interface.
/// In other words, `T::Vtable` must be equivalent to the beginning of `Self::Vtable`.
#[doc(hidden)]
#[inline(always)]
unsafe fn assume_vtable<T: Interface>(&self) -> &T::Vtable {
&**(self.as_raw() as *mut *mut T::Vtable)
}
/// Returns the raw COM interface pointer. The resulting pointer continues to be owned by the `Interface` implementation.
#[inline(always)]
fn as_raw(&self) -> *mut c_void {
// SAFETY: implementors of this trait must guarantee that the implementing type has a pointer in-memory representation
unsafe { transmute_copy(self) }
}
/// Returns the raw COM interface pointer and releases ownership. It the caller's responsibility to release the COM interface pointer.
#[inline(always)]
fn into_raw(self) -> *mut c_void {
// SAFETY: implementors of this trait must guarantee that the implementing type has a pointer in-memory representation
let raw = self.as_raw();
forget(self);
raw
}
/// Creates an `Interface` by taking ownership of the `raw` COM interface pointer.
///
/// # Safety
///
/// The `raw` pointer must be owned by the caller and represent a valid COM interface pointer. In other words,
/// it must point to a vtable beginning with the `IUnknown` function pointers and match the vtable of `Interface`.
unsafe fn from_raw(raw: *mut c_void) -> Self {
transmute_copy(&raw)
}
/// Creates an `Interface` that is valid so long as the `raw` COM interface pointer is valid.
///
/// # Safety
///
/// The `raw` pointer must be a valid COM interface pointer. In other words, it must point to a vtable
/// beginning with the `IUnknown` function pointers and match the vtable of `Interface`.
#[inline(always)]
unsafe fn from_raw_borrowed(raw: &*mut c_void) -> Option<&Self> {
if raw.is_null() {
None
} else {
Some(transmute_copy(&raw))
}
}
/// Attempts to cast the current interface to another interface using `QueryInterface`.
///
/// The name `cast` is preferred to `query` because there is a WinRT method named query but not one
/// named cast.
#[inline(always)]
fn cast<T: Interface>(&self) -> Result<T> {
// SAFETY: `result` is valid for writing an interface pointer and it is safe
// to cast the `result` pointer as `T` on success because we are using the `IID` tied
// to `T` which the implementor of `Interface` has guaranteed is correct
unsafe {
// If query() returns a failure code then we propagate that failure code to the caller.
// In that case, we ignore the contents of 'result' (which will _not_ be dropped,
// because MaybeUninit intentionally does not drop its contents).
//
// This guards against implementations of COM interfaces which may store non-null values
// in 'result' but still return E_NOINTERFACE.
let mut result = MaybeUninit::<Option<T>>::zeroed();
self.query(&T::IID, result.as_mut_ptr() as _).ok()?;
// If we get here, then query() has succeeded, but we still need to double-check
// that the output pointer is non-null.
if let Some(obj) = result.assume_init() {
Ok(obj)
} else {
Err(imp::E_POINTER.into())
}
}
}
/// This casts the given COM interface to [`&dyn Any`].
///
/// Applications should generally _not_ call this method directly. Instead, use the
/// [`Interface::cast_object_ref`] or [`Interface::cast_object`] methods.
///
/// `T` must be a type that has been annotated with `#[implement]`; this is checked at
/// compile-time by the generic constraints of this method. However, note that the
/// returned `&dyn Any` refers to the _outer_ implementation object that was generated by
/// `#[implement]`, i.e. the `MyApp_Impl` type, not the inner `MyApp` type.
///
/// If the given object is not a Rust object, or is a Rust object but not `T`, or is a Rust
/// object that contains non-static lifetimes, then this function will return `Err(E_NOINTERFACE)`.
///
/// # Safety
///
/// **IMPORTANT!!** This uses a non-standard protocol for QueryInterface! The `DYNAMIC_CAST_IID`
/// IID identifies this protocol, but there is no `IDynamicCast` interface. Instead, objects
/// that recognize `DYNAMIC_CAST_IID` simply store their `&dyn Any` directly at the interface
/// pointer that was passed to `QueryInterface. This means that the returned value has a
/// size that is twice as large (`size_of::<&dyn Any>() == 2 * size_of::<*const c_void>()`).
///
/// This means that callers that use this protocol cannot simply pass `&mut ptr` for
/// an ordinary single-pointer-sized pointer. Only this method understands this protocol.
///
/// Another part of this protocol is that the implementation of `QueryInterface` _does not_
/// AddRef the object. The caller must guarantee the liveness of the COM object. In Rust,
/// this means tying the lifetime of the IUnknown* that we used for the QueryInterface
/// call to the lifetime of the returned `&dyn Any` value.
///
/// This method preserves type safety and relies on these invariants:
///
/// * All `QueryInterface` implementations that recognize `DYNAMIC_CAST_IID` are generated by
/// the `#[implement]` macro and respect the rules described here.
#[inline(always)]
fn cast_to_any<T>(&self) -> Result<&dyn Any>
where
T: ComObjectInner,
T::Outer: Any + 'static + IUnknownImpl<Impl = T>,
{
unsafe {
let mut any_ref_arg: MaybeUninit<&dyn Any> = MaybeUninit::zeroed();
self.query(
&DYNAMIC_CAST_IID,
any_ref_arg.as_mut_ptr() as *mut *mut c_void,
)
.ok()?;
Ok(any_ref_arg.assume_init())
}
}
/// Returns `true` if the given COM interface refers to an implementation of `T`.
///
/// `T` must be a type that has been annotated with `#[implement]`; this is checked at
/// compile-time by the generic constraints of this method.
///
/// If the given object is not a Rust object, or is a Rust object but not `T`, or is a Rust
/// object that contains non-static lifetimes, then this function will return `false`.
#[inline(always)]
fn is_object<T>(&self) -> bool
where
T: ComObjectInner,
T::Outer: Any + 'static + IUnknownImpl<Impl = T>,
{
if let Ok(any) = self.cast_to_any::<T>() {
any.is::<T::Outer>()
} else {
false
}
}
/// This casts the given COM interface to [`&dyn Any`]. It returns a reference to the "outer"
/// object, e.g. `&MyApp_Impl`, not the inner `&MyApp` object.
///
/// `T` must be a type that has been annotated with `#[implement]`; this is checked at
/// compile-time by the generic constraints of this method. However, note that the
/// returned `&dyn Any` refers to the _outer_ implementation object that was generated by
/// `#[implement]`, i.e. the `MyApp_Impl` type, not the inner `MyApp` type.
///
/// If the given object is not a Rust object, or is a Rust object but not `T`, or is a Rust
/// object that contains non-static lifetimes, then this function will return `Err(E_NOINTERFACE)`.
///
/// The returned value is borrowed. If you need an owned (counted) reference, then use
/// [`Interface::cast_object`].
#[inline(always)]
fn cast_object_ref<T>(&self) -> Result<&T::Outer>
where
T: ComObjectInner,
T::Outer: Any + 'static + IUnknownImpl<Impl = T>,
{
let any: &dyn Any = self.cast_to_any::<T>()?;
if let Some(outer) = any.downcast_ref::<T::Outer>() {
Ok(outer)
} else {
Err(imp::E_NOINTERFACE.into())
}
}
/// This casts the given COM interface to [`&dyn Any`]. It returns a reference to the "outer"
/// object, e.g. `MyApp_Impl`, not the inner `MyApp` object.
///
/// `T` must be a type that has been annotated with `#[implement]`; this is checked at
/// compile-time by the generic constraints of this method. However, note that the
/// returned `&dyn Any` refers to the _outer_ implementation object that was generated by
/// `#[implement]`, i.e. the `MyApp_Impl` type, not the inner `MyApp` type.
///
/// If the given object is not a Rust object, or is a Rust object but not `T`, or is a Rust
/// object that contains non-static lifetimes, then this function will return `Err(E_NOINTERFACE)`.
///
/// The returned value is an owned (counted) reference; this function calls `AddRef` on the
/// underlying COM object. If you do not need an owned reference, then you can use the
/// [`Interface::cast_object_ref`] method instead, and avoid the cost of `AddRef` / `Release`.
#[inline(always)]
fn cast_object<T>(&self) -> Result<ComObject<T>>
where
T: ComObjectInner,
T::Outer: Any + 'static + IUnknownImpl<Impl = T>,
{
let object_ref = self.cast_object_ref::<T>()?;
Ok(object_ref.to_object())
}
/// Attempts to create a [`Weak`] reference to this object.
fn downgrade(&self) -> Result<Weak<Self>> {
self.cast::<imp::IWeakReferenceSource>()
.and_then(|source| Weak::downgrade(&source))
}
/// Call `QueryInterface` on this interface
///
/// # Safety
///
/// `interface` must be a non-null, valid pointer for writing an interface pointer.
#[inline(always)]
unsafe fn query(&self, iid: *const GUID, interface: *mut *mut c_void) -> HRESULT {
if Self::UNKNOWN {
(self.assume_vtable::<IUnknown>().QueryInterface)(self.as_raw(), iid, interface)
} else {
panic!("Non-COM interfaces cannot be queried.")
}
}
/// Creates an `InterfaceRef` for this reference. The `InterfaceRef` tracks lifetimes statically,
/// and eliminates the need for dynamic reference count adjustments (AddRef/Release).
fn to_ref(&self) -> InterfaceRef<'_, Self> {
InterfaceRef::from_interface(self)
}
}
/// # Safety
#[doc(hidden)]
pub unsafe fn from_raw_borrowed<T: Interface>(raw: &*mut c_void) -> Option<&T> {
T::from_raw_borrowed(raw)
}
/// This has the same memory representation as `IFoo`, but represents a borrowed interface pointer.
///
/// This type has no `Drop` impl; it does not AddRef/Release the given interface. However, because
/// it has a lifetime parameter, it always represents a non-null pointer to an interface.
#[repr(transparent)]
pub struct InterfaceRef<'a, I>(NonNull<c_void>, PhantomData<&'a I>);
impl<'a, I> Copy for InterfaceRef<'a, I> {}
impl<'a, I> Clone for InterfaceRef<'a, I> {
fn clone(&self) -> Self {
*self
}
}
impl<'a, I: core::fmt::Debug + Interface> core::fmt::Debug for InterfaceRef<'a, I> {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
<I as core::fmt::Debug>::fmt(&**self, f)
}
}
impl<'a, I: Interface> InterfaceRef<'a, I> {
/// Creates an `InterfaceRef` from a raw pointer. _This is extremely dangerous, since there
/// is no lifetime tracking at all!_
///
/// # Safety
/// The caller must guarantee that the `'a` lifetime parameter is bound by context to a correct
/// lifetime.
#[inline(always)]
pub unsafe fn from_raw(ptr: NonNull<c_void>) -> Self {
Self(ptr, PhantomData)
}
/// Creates an `InterfaceRef` from an interface reference. This safely associates the lifetime
/// of the interface reference with the `'a` parameter of `InterfaceRef`. This allows for
/// lifetime checking _without_ calling AddRef/Release on the underlying lifetime, which can
/// improve efficiency.
#[inline(always)]
pub fn from_interface(interface: &I) -> Self {
unsafe {
// SAFETY: new_unchecked() should be valid because Interface::as_raw should always
// return a non-null pointer.
Self(NonNull::new_unchecked(interface.as_raw()), PhantomData)
}
}
/// Calls AddRef on the underlying COM interface and returns an "owned" (counted) reference.
#[inline(always)]
pub fn to_owned(self) -> I {
(*self).clone()
}
}
impl<'a, 'i: 'a, I: Interface> From<&'i I> for InterfaceRef<'a, I> {
#[inline(always)]
fn from(interface: &'a I) -> InterfaceRef<'a, I> {
InterfaceRef::from_interface(interface)
}
}
impl<'a, I: Interface> core::ops::Deref for InterfaceRef<'a, I> {
type Target = I;
#[inline(always)]
fn deref(&self) -> &I {
unsafe { core::mem::transmute(self) }
}
}
/// This IID identifies a special protocol, used by [`Interface::cast_to_any`]. This is _not_
/// an ordinary COM interface; it uses special lifetime rules and a larger interface pointer.
/// See the comments on [`Interface::cast_to_any`].
#[doc(hidden)]
pub const DYNAMIC_CAST_IID: GUID = GUID::from_u128(0xae49d5cb_143f_431c_874c_2729336e4eca);