ThrottledStream2

ThrottledStream2.cs

// source: https://stackoverflow.com/a/42133563
public class ThrottledStream2 : Stream
    {
        private readonly Stream parent;
        private readonly int maxBytesPerSecond;
        private readonly Stopwatch stopwatch;

        private long processed;

        public ThrottledStream2(Stream parent, int maxBytesPerSecond)
        {
            this.maxBytesPerSecond = maxBytesPerSecond;
            this.parent = parent;
            stopwatch = Stopwatch.StartNew();
            processed = 0;
        }

        protected async Task Throttle(int bytes)
        {
            processed += bytes;
            var targetTime = TimeSpan.FromSeconds((double)processed / maxBytesPerSecond);
            var actualTime = stopwatch.Elapsed;
            var sleep = targetTime - actualTime;
            if (sleep > TimeSpan.Zero)
            {
                await Task.Delay(sleep).ConfigureAwait(false);
            }
        }

        public override bool CanRead => parent.CanRead;

        public override bool CanSeek => parent.CanSeek;

        public override bool CanWrite => parent.CanWrite;

        public override void Flush() => parent.Flush();

        public override long Length => parent.Length;

        public override long Position
        {
            get => parent.Position;
            set => parent.Position = value;
        }

        public override async Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
        {
            var numberOfBytesRead = await parent.ReadAsync(buffer, offset, count, cancellationToken).ConfigureAwait(false);
            await Throttle(numberOfBytesRead).ConfigureAwait(false);
            return numberOfBytesRead;
        }

        public override int Read(byte[] buffer, int offset, int count) => throw new NotSupportedException();

        public override long Seek(long offset, SeekOrigin origin) => parent.Seek(offset, origin);

        public override void SetLength(long value) => parent.SetLength(value);

        public override void Write(byte[] buffer, int offset, int count) => throw new NotSupportedException();
    }