New file from zeo-1_0-branch.

Wrap asyncore calls and be careful about exceptions.

trunk/src/ZEO/asyncwrap.py

+"""A wrapper for asyncore that provides robust exception handling.
+
+The poll() and loop() calls exported by asyncore can raise exceptions.
+asyncore uses either the select() or poll() system call.  It is
+possible for those system calls to fail, returning, for example,
+EINTR.  Python raises a select.error when an error occurs.  If the
+program using asyncore doesn't catch the exception, it will die with
+an uncaught exception.
+
+This module exports safer versions of loop() and poll() that wrap the
+asyncore calls in try/except handlers that catch the errors and do the
+right thing.  In most cases, it is safe to catch the error and simply
+retry the call.
+
+XXX Operations on asyncore sockets can also fail with exceptions that
+can safely be caught and ignored by user programs.  It's not clear if
+it would be useful to extend this module with wrappers for those
+errors.
+"""
+
+# XXX The current implementation requires Python 2.0.  Not sure if
+# that's acceptable, depends on how many users want to combine ZEO 1.0
+# and Zope 2.3.
+
+import asyncore
+import errno
+import select
+
+def loop(*args, **kwargs):
+    while 1:
+        try:
+            apply(asyncore.loop, args, kwargs)
+        except select.error, err:
+            if err[0] != errno.EINTR:
+                raise
+        else:
+            break
+    
+def poll(*args, **kwargs):
+    try:
+        apply(asyncore.poll, args, kwargs)
+    except select.error, err:
+        if err[0] != errno.EINTR:
+            raise