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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
namespace Microsoft.Interop
{
/// <summary>
/// This method provides a wrapper for an <see cref="ImmutableArray{T}" /> that overrides the equality operation to provide elementwise comparison.
/// The default equality operation for an <see cref="ImmutableArray{T}" /> is reference equality of the underlying array, which is too strict
/// for many scenarios. This wrapper type allows us to use <see cref="ImmutableArray{T}" />s in our other record types without having to write an Equals method
/// that we may forget to update if we add new elements to the record.
/// </summary>
public readonly record struct SequenceEqualImmutableArray<T>(ImmutableArray<T> Array, IEqualityComparer<T> Comparer) : IEnumerable<T>
{
public SequenceEqualImmutableArray(ImmutableArray<T> array)
: this(array, EqualityComparer<T>.Default)
{
}
public SequenceEqualImmutableArray<T> Add(T value)
{
return new SequenceEqualImmutableArray<T>(Array.Add(value));
}
public T this[int i] { get => Array[i]; }
public int Length => Array.Length;
public SequenceEqualImmutableArray<T> Insert(int index, T item)
=> new SequenceEqualImmutableArray<T>(Array.Insert(index, item), Comparer);
public override int GetHashCode() => HashCode.SequentialValuesHash(Array);
public bool Equals(SequenceEqualImmutableArray<T> other)
{
return Array.SequenceEqual(other.Array, Comparer);
}
public IEnumerator<T> GetEnumerator() => ((IEnumerable<T>)Array).GetEnumerator();
IEnumerator IEnumerable.GetEnumerator() => ((IEnumerable)Array).GetEnumerator();
}
public static partial class CollectionExtensions
{
public static SequenceEqualImmutableArray<T> ToSequenceEqualImmutableArray<T>(this IEnumerable<T> source, IEqualityComparer<T> comparer)
{
return new(source.ToImmutableArray(), comparer);
}
public static SequenceEqualImmutableArray<T> ToSequenceEqualImmutableArray<T>(this IEnumerable<T> source)
{
return new(source.ToImmutableArray());
}
public static SequenceEqualImmutableArray<T> ToSequenceEqual<T>(this ImmutableArray<T> source)
{
return new(source);
}
}
}
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