69 lines
2.1 KiB
C#
69 lines
2.1 KiB
C#
// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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// See the LICENSE file in the project root for more information.
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using System;
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using System.Collections.Generic;
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namespace CommunityToolkit.Mvvm.SourceGenerators.Helpers;
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/// <summary>
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/// A base <see cref="IEqualityComparer{T}"/> implementation for <typeparamref name="T"/> instances.
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/// </summary>
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/// <typeparam name="T">The type of items to compare.</typeparam>
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/// <typeparam name="TSelf">The concrete comparer type.</typeparam>
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internal abstract class Comparer<T, TSelf> : IEqualityComparer<T>
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where TSelf : Comparer<T, TSelf>, new()
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{
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/// <summary>
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/// The singleton <typeparamref name="TSelf"/> instance.
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/// </summary>
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public static TSelf Default { get; } = new();
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/// <inheritdoc/>
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public bool Equals(T? x, T? y)
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{
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if (x is null && y is null)
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{
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return true;
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}
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if (x is null || y is null)
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{
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return false;
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}
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if (ReferenceEquals(x, y))
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{
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return true;
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}
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return AreEqual(x, y);
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}
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/// <inheritdoc/>
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public int GetHashCode(T obj)
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{
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HashCode hashCode = default;
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AddToHashCode(ref hashCode, obj);
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return hashCode.ToHashCode();
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}
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/// <summary>
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/// Adds the current instance to an incremental <see cref="HashCode"/> value.
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/// </summary>
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/// <param name="hashCode">The target <see cref="HashCode"/> value.</param>
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/// <param name="obj">The <typeparamref name="T"/> instance being inspected.</param>
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protected abstract void AddToHashCode(ref HashCode hashCode, T obj);
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/// <summary>
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/// Compares two <typeparamref name="T"/> instances for equality.
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/// </summary>
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/// <param name="x">The first <typeparamref name="T"/> instance to compare.</param>
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/// <param name="y">The second <typeparamref name="T"/> instance to compare.</param>
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/// <returns>Whether or not <paramref name="x"/> and <paramref name="y"/> are equal.</returns>
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protected abstract bool AreEqual(T x, T y);
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}
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