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//! Everything related to the [IUnknown](https://docs.microsoft.com/en-us/windows/win32/api/unknwn/nn-unknwn-iunknown) COM interface use crate::sys::{E_NOINTERFACE, E_POINTER, FAILED}; use crate::sys::{GUID, HRESULT}; use crate::{interfaces, Interface, IID}; use std::ffi::c_void; interfaces! { /// [IUnknown](https://docs.microsoft.com/en-us/windows/win32/api/unknwn/nn-unknwn-iunknown) COM interface #[uuid("00000000-0000-0000-C000-000000000046")] pub unsafe interface IUnknown { /// The COM [`QueryInterface` Method] /// /// This method normally should not be called directly. Interfaces that implement /// `IUnknown` also implement [`IUnknown::query_interface`] which is a safe wrapper around /// `IUnknown::QueryInterface`. /// /// [`QueryInterface` Method]: https://docs.microsoft.com/en-us/windows/win32/api/unknwn/nf-unknwn-iunknown-queryinterface(refiid_void) /// [`IUnknown::query_interface`]: trait.IUnknown.html#method.query_interface pub unsafe fn QueryInterface(&self, riid: *const GUID, ppv: *mut *mut c_void) -> HRESULT; /// The COM [`AddRef` Method] /// /// This method normally should not be called directly. This method is used by /// [`ComPtr`] to implement the reference counting mechanism. /// /// [`AddRef` Method]: https://docs.microsoft.com/en-us/windows/win32/api/unknwn/nf-unknwn-iunknown-addref /// [`ComPtr`]: struct.ComPtr.html pub unsafe fn AddRef(&self) -> u32; /// The COM [`Release` Method] /// /// This method normally should not be called directly. This method is used by /// [`ComPtr`] to implement the reference counting mechanism. /// /// [`Release` Method]: https://docs.microsoft.com/en-us/windows/win32/api/unknwn/nf-unknwn-iunknown-release /// [`ComPtr`]: struct.ComPtr.html pub unsafe fn Release(&self) -> u32; } } impl IUnknown { /// A safe version of `QueryInterface`. /// /// If the backing class implements the interface `I` then a `Some` /// containing an `ComPtr` pointing to that interface will be returned /// otherwise `None` will be returned. pub fn query_interface<I: Interface>(&self) -> Option<I> { let mut ppv = None; let hr = unsafe { self.QueryInterface( &I::IID as *const IID, &mut ppv as *mut _ as *mut *mut c_void, ) }; if FAILED(hr) { assert!( hr == E_NOINTERFACE || hr == E_POINTER, "QueryInterface returned non-standard error" ); return None; } debug_assert!(ppv.is_some()); ppv } }