uasyncio: Switch to builtin uselect.poll() object.

This is a big step towards supporting uasyncio on baremetal builds (and
on unix builds without FFI support).

uasyncio/uasyncio/__init__.py

@@ -1,5 +1,5 @@
 import errno
-import select
+import uselect as select
 import usocket as _socket
 from uasyncio.core import *
 
@@ -8,34 +8,41 @@ class EpollEventLoop(EventLoop):
 
     def __init__(self):
         EventLoop.__init__(self)
-        self.poller = select.epoll(1)
+        self.poller = select.poll()
+        self.objmap = {}
 
     def add_reader(self, fd, cb, *args):
         if __debug__:
             log.debug("add_reader%s", (fd, cb, args))
         if args:
-            self.poller.register(fd, select.EPOLLIN | select.EPOLLONESHOT, (cb, args))
+            self.poller.register(fd, select.POLLIN)
+            self.objmap[fd] = (cb, args)
         else:
-            self.poller.register(fd, select.EPOLLIN | select.EPOLLONESHOT, cb)
+            self.poller.register(fd, select.POLLIN)
+            self.objmap[fd] = cb
 
     def remove_reader(self, fd):
         if __debug__:
             log.debug("remove_reader(%s)", fd)
         self.poller.unregister(fd)
+        del self.objmap[fd]
 
     def add_writer(self, fd, cb, *args):
         if __debug__:
             log.debug("add_writer%s", (fd, cb, args))
         if args:
-            self.poller.register(fd, select.EPOLLOUT | select.EPOLLONESHOT, (cb, args))
+            self.poller.register(fd, select.POLLOUT)
+            self.objmap[fd] = (cb, args)
         else:
-            self.poller.register(fd, select.EPOLLOUT | select.EPOLLONESHOT, cb)
+            self.poller.register(fd, select.POLLOUT)
+            self.objmap[fd] = cb
 
     def remove_writer(self, fd):
         if __debug__:
             log.debug("remove_writer(%s)", fd)
         try:
             self.poller.unregister(fd)
+            self.objmap.pop(fd, None)
         except OSError as e:
             # StreamWriter.awrite() first tries to write to an fd,
             # and if that succeeds, yield IOWrite may never be called
@@ -47,12 +54,14 @@ class EpollEventLoop(EventLoop):
     def wait(self, delay):
         if __debug__:
             log.debug("epoll.wait(%d)", delay)
+        # We need one-shot behavior (second arg of 1 to .poll())
         if delay == -1:
-            res = self.poller.poll(-1)
+            res = self.poller.poll(-1, 1)
         else:
-            res = self.poller.poll(int(delay * 1000))
+            res = self.poller.poll(int(delay * 1000), 1)
         #log.debug("epoll result: %s", res)
-        for cb, ev in res:
+        for fd, ev in res:
+            cb = self.objmap[fd]
             if __debug__:
                 log.debug("Calling IO callback: %r", cb)
             if isinstance(cb, tuple):