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Add non-generic ComScope for handling arbitrary COM objects
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| // Copyright (c) Jeremy W. Kuhne. All rights reserved. | ||
| // Licensed under the MIT license. See LICENSE file in the project root for full license information. | ||
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| // Based on https://github.com/dotnet/winforms/blob/main/src/System.Windows.Forms.Primitives/src/Windows/Win32/Foundation/ComScope.cs | ||
| // | ||
| // Original header | ||
| // --------------- | ||
| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
| // See the LICENSE file in the project root for more information. | ||
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| using System.Runtime.CompilerServices; | ||
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| namespace Windows.Win32.System.Com; | ||
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| /// <summary> | ||
| /// Lifetime management struct for a native COM pointer. Meant to be utilized in a <see langword="using"/> statement | ||
| /// to ensure <see cref="IUnknown.Release(IUnknown*)"/> is called when going out of scope with the using. | ||
| /// </summary> | ||
| /// <remarks> | ||
| /// <para> | ||
| /// This struct has implicit conversions to T** and void** so it can be passed directly to out methods. | ||
| /// For example: | ||
| /// </para> | ||
| /// <code> | ||
| /// using ComScope<IUnknown> unknown = new(null); | ||
| /// comObject->QueryInterface(&iid, unknown); | ||
| /// </code> | ||
| /// <para> | ||
| /// Take care to NOT make copies of the struct to avoid accidental over-release. | ||
| /// </para> | ||
| /// </remarks> | ||
| /// <typeparam name="T"> | ||
| /// This should be one of the struct COM definitions as generated by CsWin32. | ||
| /// </typeparam> | ||
| public readonly unsafe ref struct ComScope<T> where T : unmanaged, IComIID | ||
| { | ||
| // Keeping internal as nint allows us to use Unsafe methods to get significantly better generated code. | ||
| private readonly nint _value; | ||
| public T* Value => (T*)_value; | ||
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| public ComScope(T* value) => _value = (nint)value; | ||
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| public ComScope(void* value) => _value = (nint)value; | ||
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| public static implicit operator T*(in ComScope<T> scope) => (T*)scope._value; | ||
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| public static implicit operator void*(in ComScope<T> scope) => (void*)scope._value; | ||
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| public static implicit operator nint(in ComScope<T> scope) => scope._value; | ||
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| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| public static implicit operator T**(in ComScope<T> scope) => (T**)Unsafe.AsPointer(ref Unsafe.AsRef(in scope._value)); | ||
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| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| public static implicit operator void**(in ComScope<T> scope) => (void**)Unsafe.AsPointer(ref Unsafe.AsRef(in scope._value)); | ||
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| public bool IsNull => _value == 0; | ||
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| public ComScope<TInterface> QueryInterface<TInterface>() where TInterface : unmanaged, IComIID | ||
| { | ||
| ComScope<TInterface> scope = new(null); | ||
| ((IUnknown*)Value)->QueryInterface(IID.Get<TInterface>(), scope).ThrowOnFailure(); | ||
| return scope; | ||
| } | ||
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| public ComScope<TInterface> TryQueryInterface<TInterface>() where TInterface : unmanaged, IComIID | ||
| => TryQueryInterface<TInterface>(out _); | ||
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| public ComScope<TInterface> TryQueryInterface<TInterface>(out HRESULT result) where TInterface : unmanaged, IComIID | ||
| { | ||
| ComScope<TInterface> scope = new(null); | ||
| result = ((IUnknown*)Value)->QueryInterface(IID.Get<TInterface>(), scope); | ||
| return scope; | ||
| } | ||
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| public static ComScope<T> TryQueryFrom<TFrom>(TFrom* from, out HRESULT result) where TFrom : unmanaged, IComIID | ||
| { | ||
| ComScope<T> scope = new(null); | ||
| result = from is null ? HRESULT.E_POINTER : ((IUnknown*)from)->QueryInterface(IID.Get<T>(), scope); | ||
| return scope; | ||
| } | ||
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| public static ComScope<T> QueryFrom<TFrom>(TFrom* from) where TFrom : unmanaged, IComIID | ||
| { | ||
| ComScope<T> scope = new(null); | ||
| if (from is null) | ||
| { | ||
| HRESULT.E_POINTER.ThrowOnFailure(); | ||
| } | ||
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| ((IUnknown*)from)->QueryInterface(IID.Get<T>(), scope).ThrowOnFailure(); | ||
| return scope; | ||
| } | ||
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| /// <summary> | ||
| /// Gets a COM callable wrapper (CCW) for the given <paramref name="obj"/>. | ||
| /// </summary> | ||
| public static ComScope<T> GetComCallableWrapper(object? obj) | ||
| => new(ComHelpers.GetComPointer<T>(obj)); | ||
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| public static ComScope<T> TryGetComCallableWrapper(object? obj, out HRESULT result) | ||
| => new(ComHelpers.TryGetComPointer<T>(obj, out result)); | ||
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| public void Dispose() | ||
| { | ||
| IUnknown* unknown = (IUnknown*)_value; | ||
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| // Really want this to be null after disposal to avoid double releases, but we also want | ||
| // to maintain the readonly state of the struct to allow passing as `in` without creating implicit | ||
| // copies (which would break the T** and void** operators). | ||
| *(void**)this = null; | ||
| if (unknown is not null) | ||
| { | ||
| unknown->Release(); | ||
| } | ||
| } | ||
| } |