C＃使用span与SocketAsyncEventArgs

Question

I would like to use new Span to send unmanaged data straight to the socket using SocketAsyncEventArgs but it seems that SocketAsyncEventArgs can only accept Memory<byte> which cannot be initialized with byte * or IntPt r.

So please is there a way to do use span with SocketAsyncEventArgs ?

Thank you for your help.

Answer 1

As already mentioned in the comments, Span is the wrong tool here - have you looked at using Memory instead? As you stated, the SetBuffer method does accept that as a parameter - is there a reason you can't use it?

See also this article for a good explanation on how stack vs heap allocation applies to Span and Memory. It includes this example, using a readonly Memory<Foo> buffer :

public struct Enumerable : IEnumerable<Foo>
{
    readonly Stream stream;

    public Enumerable(Stream stream)
    {
        this.stream = stream;
    }

    public IEnumerator<Foo> GetEnumerator() => new Enumerator(this);

    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();

    public struct Enumerator : IEnumerator<Foo>
    {
        static readonly int ItemSize = Unsafe.SizeOf<Foo>();

        readonly Stream stream;
        readonly Memory<Foo> buffer;
        bool lastBuffer;
        long loadedItems;
        int currentItem;

        public Enumerator(Enumerable enumerable)
        {
            stream = enumerable.stream;
            buffer = new Foo[100]; // alloc items buffer
            lastBuffer = false;
            loadedItems = 0;
            currentItem = -1;
        }

        public Foo Current => buffer.Span[currentItem];

        object IEnumerator.Current => Current;

        public bool MoveNext()
        {
            if (++currentItem != loadedItems) // increment current position and check if reached end of buffer
                return true;
            if (lastBuffer) // check if it was the last buffer
                return false;

            // get next buffer
            var rawBuffer = MemoryMarshal.Cast<Foo, byte>(buffer);
            var bytesRead = stream.Read(rawBuffer);
            lastBuffer = bytesRead < rawBuffer.Length;
            currentItem = 0;
            loadedItems = bytesRead / ItemSize;
            return loadedItems != 0;
        }

        public void Reset() => throw new NotImplementedException();

        public void Dispose()
        {
            // nothing to do
        }
    }
}

Answer 2

You should copy the data to managed memory first, use Marshal or Buffer class.

If not think about when the C code delete the returned pointer what will happen to the send data?

Answer 3

There's a complete example (and implementation of the class) on the MSDN page for the SocketAsyncEventArgs (just follow the link) . It shows the proper use of the class and may give you the guidence you're looking for.

Also, as Shingo said, it should all be in managed code, not in pointers.