public override Task CopyToAsync()

in src/RecyclableMemoryStream.cs [557:615]
54 lines of code
7 McCabe index (conditional complexity)

        public override Task CopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken)
        {
            if (destination == null)
            {
                throw new ArgumentNullException(nameof(destination));
            }

            this.CheckDisposed();

            if (this.length == 0)
            {
                return Task.CompletedTask;
            }

            long startPos = this.position;
            var count = this.length - startPos;
            this.position += count;

            if (destination is MemoryStream destinationRMS)
            {
                this.WriteTo(destinationRMS, startPos, count);
                return Task.CompletedTask;
            }
            else
            {
                if (this.largeBuffer == null)
                {
                    if (this.blocks.Count == 1)
                    {
                        AssertLengthIsSmall();
                        return destination.WriteAsync(this.blocks[0], (int)startPos, (int)count, cancellationToken);
                    }
                    else
                    {
                        return CopyToAsyncImpl(destination, this.GetBlockAndRelativeOffset(startPos), count, this.blocks, cancellationToken);
                    }
                }
                else
                {
                    AssertLengthIsSmall();
                    return destination.WriteAsync(this.largeBuffer, (int)startPos, (int)count, cancellationToken);
                }
            }

            static async Task CopyToAsyncImpl(Stream destination, BlockAndOffset blockAndOffset, long count, List<byte[]> blocks, CancellationToken cancellationToken)
            {
                var bytesRemaining = count;
                int currentBlock = blockAndOffset.Block;
                var currentOffset = blockAndOffset.Offset;
                while (bytesRemaining > 0)
                {
                    int amountToCopy = (int)Math.Min(blocks[currentBlock].Length - currentOffset, bytesRemaining);
                    await destination.WriteAsync(blocks[currentBlock], currentOffset, amountToCopy, cancellationToken);
                    bytesRemaining -= amountToCopy;
                    ++currentBlock;
                    currentOffset = 0;
                }
            }
        }