System.Net.Sockets.SocketPal.Select C# (CSharp) Метод

        public static unsafe SocketError Select(IList checkRead, IList checkWrite, IList checkError, int microseconds)
        {
            int checkReadInitialCount = checkRead != null ? checkRead.Count : 0;
            int checkWriteInitialCount = checkWrite != null ? checkWrite.Count : 0;
            int checkErrorInitialCount = checkError != null ? checkError.Count : 0;
            int count = checked(checkReadInitialCount + checkWriteInitialCount + checkErrorInitialCount);
            Debug.Assert(count > 0, $"Expected at least one entry.");

            // Rather than using the select syscall, we use poll.  While this has a mismatch in API from Select and
            // requires some translation, it avoids the significant limitation of select only working with file descriptors
            // less than FD_SETSIZE, and thus failing arbitrarily depending on the file descriptor value assigned
            // by the system.  Since poll then expects an array of entries, we try to allocate the array on the stack,
            // only falling back to allocating it on the heap if it's deemed too big.

            const int StackThreshold = 80; // arbitrary limit to avoid too much space on stack
            if (count < StackThreshold)
            {
                Interop.Sys.PollEvent* eventsOnStack = stackalloc Interop.Sys.PollEvent[count];
                return SelectViaPoll(
                    checkRead, checkReadInitialCount,
                    checkWrite, checkWriteInitialCount,
                    checkError, checkErrorInitialCount,
                    eventsOnStack, count, microseconds);
            }
            else
            {
                var eventsOnHeap = new Interop.Sys.PollEvent[count];
                fixed (Interop.Sys.PollEvent* eventsOnHeapPtr = eventsOnHeap)
                {
                    return SelectViaPoll(
                        checkRead, checkReadInitialCount,
                        checkWrite, checkWriteInitialCount,
                        checkError, checkErrorInitialCount,
                        eventsOnHeapPtr, count, microseconds);
                }
            }
        }