select: in case an event creation fails, cancel all the allocated events so far

- signal error via select.error exception that is imported from stdlib's select

gevent/select.py

@@ -4,7 +4,11 @@ from gevent import core
 from gevent.hub import get_hub, getcurrent
 from gevent.timeout import Timeout
 
-__all__ = ['select']
+__all__ = ['error', 'select']
+
+__select__ = __import__('select')
+error = __select__.error
+
 
 def get_fileno(obj):
     try:
@@ -17,6 +21,16 @@ def get_fileno(obj):
         return fileno_f()
 
 
+def _select_callback(ev, evtype):
+    current, fd = ev.arg
+    if evtype & core.EV_READ:
+        current.switch(([fd], [], []))
+    elif evtype & core.EV_WRITE:
+        current.switch(([], [fd], []))
+    else:
+        current.switch(([], [], []))
+
+
 def select(rlist, wlist, xlist, timeout=None):
     """An implementation of :meth:`select.select` that blocks only the current greenlet.
 
@@ -26,22 +40,15 @@ def select(rlist, wlist, xlist, timeout=None):
     current = getcurrent()
     assert hub is not current, 'do not call blocking functions from the mainloop'
     allevents = []
-
-    def callback(ev, evtype):
-        if evtype & core.EV_READ:
-            current.switch(([ev.arg], [], []))
-        elif evtype & core.EV_WRITE:
-            current.switch(([], [ev.arg], []))
-        else:
-            current.switch(([], [], []))
-
-    for readfd in rlist:
-        allevents.append(core.read_event(get_fileno(readfd), callback, arg=readfd))
-    for writefd in wlist:
-        allevents.append(core.write_event(get_fileno(writefd), callback, arg=writefd))
-
     timeout = Timeout.start_new(timeout)
     try:
+        try:
+            for readfd in rlist:
+                allevents.append(core.read_event(get_fileno(readfd), _select_callback, arg=(current, readfd)))
+            for writefd in wlist:
+                allevents.append(core.write_event(get_fileno(writefd), _select_callback, arg=(current, writefd)))
+        except IOError, ex:
+            raise error(*ex.args)
         try:
             result = hub.switch()
         except Timeout, ex: