CollectionExtensions.cs

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using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Runtime.CompilerServices;
 
namespace System.Dynamic.Utils;
 
internal static class CollectionExtensions
{
    public static TrueReadOnlyCollection<T> AddFirst<T>(this ReadOnlyCollection<T> list, T item)
    {
        T[] array = new T[list.Count + 1];
        array[0] = item;
        list.CopyTo(array, 1);
        return new TrueReadOnlyCollection<T>(array);
    }
 
    public static T[] AddFirst<T>(this T[] array, T item)
    {
        T[] array2 = new T[array.Length + 1];
        array2[0] = item;
        array.CopyTo(array2, 1);
        return array2;
    }
 
    public static T[] AddLast<T>(this T[] array, T item)
    {
        T[] array2 = new T[array.Length + 1];
        array.CopyTo(array2, 0);
        array2[array.Length] = item;
        return array2;
    }
 
    public static T[] RemoveFirst<T>(this T[] array)
    {
        T[] array2 = new T[array.Length - 1];
        Array.Copy(array, 1, array2, 0, array2.Length);
        return array2;
    }
 
    public static T[] RemoveLast<T>(this T[] array)
    {
        T[] array2 = new T[array.Length - 1];
        Array.Copy(array, array2, array2.Length);
        return array2;
    }
 
    public static ReadOnlyCollection<T> ToReadOnly<T>(this IEnumerable<T> enumerable)
    {
        if (enumerable == null)
        {
            return EmptyReadOnlyCollection<T>.Instance;
        }
        if (enumerable is TrueReadOnlyCollection<T> result)
        {
            return result;
        }
        if (enumerable is ReadOnlyCollectionBuilder<T> readOnlyCollectionBuilder)
        {
            return readOnlyCollectionBuilder.ToReadOnlyCollection();
        }
        T[] array = enumerable.ToArray();
        if (array.Length != 0)
        {
            return new TrueReadOnlyCollection<T>(array);
        }
        return EmptyReadOnlyCollection<T>.Instance;
    }
 
    public static int ListHashCode<T>(this ReadOnlyCollection<T> list)
    {
        EqualityComparer<T> @default = EqualityComparer<T>.Default;
        int num = 6551;
        foreach (T item in list)
        {
            if (item != null)
            {
                num ^= (num << 5) ^ @default.GetHashCode(item);
            }
        }
        return num;
    }
 
    public static bool ListEquals<T>(this ReadOnlyCollection<T> first, ReadOnlyCollection<T> second)
    {
        if (first == second)
        {
            return true;
        }
        int count = first.Count;
        if (count != second.Count)
        {
            return false;
        }
        EqualityComparer<T> @default = EqualityComparer<T>.Default;
        for (int i = 0; i != count; i++)
        {
            if (!@default.Equals(first[i], second[i]))
            {
                return false;
            }
        }
        return true;
    }
}