+ /** Do not test this socket for readability
+ */
+ FD_WANT_NO_READ = 0x1,
+ /** Give a read event at all times when reads will not block.
+ */
+ FD_WANT_POLL_READ = 0x2,
+ /** Give a read event when there is new data to read.
+ *
+ * An event MUST be sent if there is new data to be read, and the most
+ * recent read/recv() on this FD returned EAGAIN. An event MAY be sent
+ * at any time there is data to be read on the socket.
+ */
+ FD_WANT_FAST_READ = 0x4,
+ /** Give an optional read event when reads begin to unblock
+ *
+ * This state is useful if you want to leave data in the OS receive
+ * queue but not get continuous event notifications about it, because
+ * it may not require a system call to transition from FD_WANT_FAST_READ
+ */
+ FD_WANT_EDGE_READ = 0x8,
+
+ /** Mask for all read events */
+ FD_WANT_READ_MASK = 0x0F,
+
+ /** Do not test this socket for writeability
+ */
+ FD_WANT_NO_WRITE = 0x10,
+ /** Give a write event at all times when writes will not block.
+ *
+ * You probably shouldn't use this state; if it's likely that the write
+ * will not block, try it first, then use FD_WANT_FAST_WRITE if it
+ * fails. If it's likely to block (or you are using polling-style reads)
+ * then use FD_WANT_SINGLE_WRITE.
+ */
+ FD_WANT_POLL_WRITE = 0x20,
+ /** Give a write event when writes don't block any more
+ *
+ * An event MUST be sent if writes will not block, and the most recent
+ * write/send() on this FD returned EAGAIN, or connect() returned
+ * EINPROGRESS. An event MAY be sent at any time that writes will not
+ * block.
+ *
+ * Before calling HandleEvent, a socket engine MAY change the state of
+ * the FD back to FD_WANT_EDGE_WRITE if it is simpler (for example, if a
+ * one-shot notification was registered). If further writes are needed,
+ * it is the responsibility of the event handler to change the state to
+ * one that will generate the required notifications
+ */
+ FD_WANT_FAST_WRITE = 0x40,
+ /** Give an optional write event on edge-triggered write unblock.
+ *
+ * This state is useful to avoid system calls when moving to/from
+ * FD_WANT_FAST_WRITE when writing data to a mostly-unblocked socket.
+ */
+ FD_WANT_EDGE_WRITE = 0x80,
+ /** Request a one-shot poll-style write notification. The socket will
+ * return to the FD_WANT_NO_WRITE state before HandleEvent is called.
+ */
+ FD_WANT_SINGLE_WRITE = 0x100,