uasyncio.udp: Initial attempt of UDP support for uasyncio.

API is not stable and will guaranteedly change, likely completely.

Currently, this tries to folow the same idea as TCP open_connection()
call, but that doesn't make much sense, so that will likely change.

uasyncio.udp/uasyncio/udp.py

@@ -0,0 +1,78 @@
+import uerrno
+import usocket
+from uasyncio.core import *
+
+
+DEBUG = 0
+log = None
+
+def set_debug(val):
+    global DEBUG, log
+    DEBUG = val
+    if val:
+        import logging
+        log = logging.getLogger("uasyncio.udp")
+
+
+class UdpSocket:
+
+    def __init__(self, s):
+        self.s = s
+
+    def recv(self, n):
+        try:
+            yield IORead(self.s)
+            return self.s.recv(n)
+        except:
+            #print("recv: exc, cleaning up")
+            #print(uasyncio.core._event_loop.objmap, uasyncio.core._event_loop.poller)
+            #uasyncio.core._event_loop.poller.dump()
+            yield IOReadDone(self.s)
+            #print(uasyncio.core._event_loop.objmap)
+            #uasyncio.core._event_loop.poller.dump()
+            raise
+
+    def recvfrom(self, n):
+        try:
+            yield IORead(self.s)
+            return self.s.recvfrom(n)
+        except:
+            #print("recv: exc, cleaning up")
+            #print(uasyncio.core._event_loop.objmap, uasyncio.core._event_loop.poller)
+            #uasyncio.core._event_loop.poller.dump()
+            yield IOReadDone(self.s)
+            #print(uasyncio.core._event_loop.objmap)
+            #uasyncio.core._event_loop.poller.dump()
+            raise
+
+    def asendto(self, buf, addr=None):
+        while 1:
+            res = self.s.sendto(buf, 0, addr)
+            #print("send res:", res)
+            if res == len(buf):
+                return
+            print("asento: IOWrite")
+            yield IOWrite(self.s)
+
+    def aclose(self):
+        yield IOReadDone(self.s)
+        self.s.close()
+
+
+def udp_socket(host=None, port=None):
+    if DEBUG and __debug__:
+        log.debug("udp_socket(%s, %s)", host, port)
+    s = usocket.socket(usocket.AF_INET, usocket.SOCK_DGRAM)
+    s.setblocking(False)
+    if host and port:
+        ai = usocket.getaddrinfo(host, port)
+        addr = ai[0][-1]
+        try:
+            s.connect(addr)
+        except OSError as e:
+            if e.args[0] != uerrno.EINPROGRESS:
+                raise
+        if DEBUG and __debug__:
+            log.debug("udp_socket: After connect")
+    return UdpSocket(s)
+    yield