reactive/Ix.NET/Source/System.Linq.Async/System/Linq/Operators/Create.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the Apache 2.0 License.
// See the LICENSE file in the project root for more information. 

using System.Collections.Generic;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;

namespace System.Linq
{
    public static partial class AsyncEnumerable
    {
        public static IAsyncEnumerable<T> CreateEnumerable<T>(Func<CancellationToken, IAsyncEnumerator<T>> getEnumerator)
        {
            if (getEnumerator == null)
                throw Error.ArgumentNull(nameof(getEnumerator));

            return new AnonymousAsyncEnumerable<T>(getEnumerator);
        }

        public static IAsyncEnumerator<T> CreateEnumerator<T>(Func<ValueTask<bool>> moveNext, Func<T> current, Func<ValueTask> dispose)
        {
            return AsyncEnumerator.Create(moveNext, current, dispose);
        }

        private static IAsyncEnumerator<T> CreateEnumerator<T>(Func<TaskCompletionSource<bool>, ValueTask<bool>> moveNext, Func<T> current, Func<ValueTask> dispose)
        {
            return AsyncEnumerator.Create(moveNext, current, dispose);
        }

        private sealed class AnonymousAsyncEnumerable<T> : IAsyncEnumerable<T>
        {
            private readonly Func<CancellationToken, IAsyncEnumerator<T>> _getEnumerator;

            public AnonymousAsyncEnumerable(Func<CancellationToken, IAsyncEnumerator<T>> getEnumerator)
            {
                Debug.Assert(getEnumerator != null);

                _getEnumerator = getEnumerator;
            }

            public IAsyncEnumerator<T> GetAsyncEnumerator(CancellationToken cancellationToken) => _getEnumerator(cancellationToken);
        }
    }
}