.NET-Community-Toolkit/CommunityToolkit.HighPerformance/Extensions/ListExtensions.cs

// 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.

#if NET6_0_OR_GREATER

using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace CommunityToolkit.HighPerformance;

/// <summary>
/// Helpers for working with the <see cref="List{T}"/> type.
/// </summary>
public static class ListExtensions
{
    /// <summary>
    /// Creates a new <see cref="Span{T}"/> over an input <see cref="List{T}"/> instance.
    /// </summary>
    /// <typeparam name="T">The type of elements in the input <see cref="List{T}"/> instance.</typeparam>
    /// <param name="list">The input <see cref="List{T}"/> instance.</param>
    /// <returns>A <see cref="Span{T}"/> instance with the values of <paramref name="list"/>.</returns>
    /// <remarks>
    /// Note that the returned <see cref="Span{T}"/> is only guaranteed to be valid as long as the items within
    /// <paramref name="list"/> are not modified. Doing so might cause the <see cref="List{T}"/> to swap its
    /// internal buffer, causing the returned <see cref="Span{T}"/> to become out of date. That means that in this
    /// scenario, the <see cref="Span{T}"/> would end up wrapping an array no longer in use. Always make sure to use
    /// the returned <see cref="Span{T}"/> while the target <see cref="List{T}"/> is not modified.
    /// </remarks>
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static Span<T> AsSpan<T>(this List<T>? list)
    {
        return CollectionsMarshal.AsSpan(list);
    }
}

#endif