X-Git-Url: http://xvm.mit.edu/gitweb/invirt/packages/invirt-base.git/blobdiff_plain/ff3dc91d38ee542dbb79c94ac910b43c2985b58e..e2cb1724053e67a4bb14b0b2c9d848e771d53a7e:/files/usr/share/python-support/sipb-xen-base/invirt/common.py

diff --git a/files/usr/share/python-support/sipb-xen-base/invirt/common.py b/files/usr/share/python-support/sipb-xen-base/invirt/common.py
index ca90714..77770a6 100644
--- a/files/usr/share/python-support/sipb-xen-base/invirt/common.py
+++ b/files/usr/share/python-support/sipb-xen-base/invirt/common.py
@@ -1,6 +1,8 @@
+from __future__ import with_statement
+
 import unittest
-from fcntl import flock, LOCK_EX, LOCK_UN
-from os import remove
+from fcntl import flock, LOCK_EX, LOCK_SH, LOCK_UN
+import contextlib as clib
 
 class struct(object):
     'A simple namespace object.'
@@ -21,37 +23,18 @@ def dicts2struct(x):
     else:
         return x
 
-#
-# Hacks to work around lack of Python 2.5's `with` statement.
-#
-
-def with_closing(rsrc):
-    "Utility to emulate Python 2.5's `with closing(rsrc)` context manager."
-    def wrapper(func):
-        try: return func(rsrc)
-        finally: rsrc.close()
-    return wrapper
-
-def with_lock_file(path):
-    """
-    Context manager for lock files.  Example:
-
-    @with_lock_file('/tmp/mylock')
-    def input():
-        print 'locked'
-        return raw_input()
-    # decorator is executed immediately
-    print input # prints the input text
-    """
-    def wrapper(func):
-        @with_closing(file(path, 'w'))
-        def g(f):
-            flock(f, LOCK_EX)
-            try: return func()
-            finally: flock(f, LOCK_UN)
-        remove(path)
-        return g
-    return wrapper
+@clib.contextmanager
+def lock_file(path, exclusive = True):
+    with clib.closing(file(path, 'w')) as f:
+        if exclusive:
+            locktype = LOCK_EX
+        else:
+            locktype = LOCK_SH
+        flock(f, locktype)
+        try:
+            yield
+        finally:
+            flock(f, LOCK_UN)
 
 #
 # Tests.