System.Net.Sockets.SocketAsyncEventArgs.SetupOverlappedSendPackets C# (CSharp) Method

        unsafe private void SetupOverlappedSendPackets()
        {
            int index;

            // Alloc native descriptor.
            _sendPacketsDescriptor =
                new Interop.Winsock.TransmitPacketsElement[_sendPacketsElementsFileCount + _sendPacketsElementsBufferCount];

            // Number of things to pin is number of buffers + 1 (native descriptor).
            // Ensure we have properly sized object array.
            if (_objectsToPin == null || (_objectsToPin.Length != _sendPacketsElementsBufferCount + 1))
            {
                _objectsToPin = new object[_sendPacketsElementsBufferCount + 1];
            }

            // Fill in objects to pin array. Native descriptor buffer first and then user specified buffers.
            _objectsToPin[0] = _sendPacketsDescriptor;
            index = 1;
            foreach (SendPacketsElement spe in _sendPacketsElementsInternal)
            {
                if (spe != null && spe._buffer != null && spe._count > 0)
                {
                    _objectsToPin[index] = spe._buffer;
                    index++;
                }
            }

            // Pin buffers.
            _preAllocatedOverlapped = new PreAllocatedOverlapped(CompletionPortCallback, this, _objectsToPin);
            if (NetEventSource.IsEnabled) NetEventSource.Info(this, $"new PreAllocatedOverlapped:{_preAllocatedOverlapped}");

            // Get pointer to native descriptor.
            _ptrSendPacketsDescriptor = Marshal.UnsafeAddrOfPinnedArrayElement(_sendPacketsDescriptor, 0);

            // Fill in native descriptor.
            int descriptorIndex = 0;
            int fileIndex = 0;
            foreach (SendPacketsElement spe in _sendPacketsElementsInternal)
            {
                if (spe != null)
                {
                    if (spe._buffer != null && spe._count > 0)
                    {
                        // This element is a buffer.
                        _sendPacketsDescriptor[descriptorIndex].buffer = Marshal.UnsafeAddrOfPinnedArrayElement(spe._buffer, spe._offset);
                        _sendPacketsDescriptor[descriptorIndex].length = (uint)spe._count;
                        _sendPacketsDescriptor[descriptorIndex].flags = (Interop.Winsock.TransmitPacketsElementFlags)spe._flags;
                        descriptorIndex++;
                    }
                    else if (spe._filePath != null)
                    {
                        // This element is a file.
                        _sendPacketsDescriptor[descriptorIndex].fileHandle = _sendPacketsFileHandles[fileIndex].DangerousGetHandle();
                        _sendPacketsDescriptor[descriptorIndex].fileOffset = spe._offset;
                        _sendPacketsDescriptor[descriptorIndex].length = (uint)spe._count;
                        _sendPacketsDescriptor[descriptorIndex].flags = (Interop.Winsock.TransmitPacketsElementFlags)spe._flags;
                        fileIndex++;
                        descriptorIndex++;
                    }
                }
            }

            _pinState = PinState.SendPackets;
        }