Now that we're using Python 2.5, we can actually write with statements

svn path=/trunk/packages/sipb-xen-base/; revision=1197

diff --git a/debian/changelog b/debian/changelog
index 435e984..5391977 100644 (file)
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,9 @@
+sipb-xen-base (8.23) unstable; urgency=low
+
+  * Now that we're using Python 2.5, we can actually write with statements
+
+ -- Evan Broder <broder@mit.edu>  Fri, 24 Oct 2008 03:32:00 -0400
+
 sipb-xen-base (8.22) unstable; urgency=low
 
   * Please - anything but etch. Anything!

diff --git a/debian/control b/debian/control
index 3ffb38a..5ded7ab 100644 (file)
--- a/debian/control
+++ b/debian/control
@@ -3,7 +3,7 @@ Section: base
 Priority: extra
 Maintainer: SIPB Xen Project <sipb-xen@mit.edu>
 Build-Depends: cdbs (>= 0.4.23-1.1), debhelper (>= 4.1.0), python-support
-Standards-Version: 3.7.2
+Standards-Version: 3.8.0
 
 Package: sipb-xen-base
 Architecture: all

diff --git a/debian/pyversions b/debian/pyversions
new file mode 100644 (file)
index 0000000..b3dc41e
--- /dev/null
+++ b/debian/pyversions
@@ -0,0 +1 @@
+2.5-

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 d986196..77770a6 100644 (file)
--- a/files/usr/share/python-support/sipb-xen-base/invirt/common.py
+++ b/files/usr/share/python-support/sipb-xen-base/invirt/common.py
@@ -1,5 +1,8 @@
+from __future__ import with_statement
+
 import unittest
 from fcntl import flock, LOCK_EX, LOCK_SH, LOCK_UN
+import contextlib as clib
 
 class struct(object):
     'A simple namespace object.'
@@ -20,46 +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.
-
-    E.g.,
-    @with_closing(file('/tmp/foo'))
-    def contents(f):
-        return f.read()
-    # now 'contents' is the contents of /tmp/foo
-    """
-    def wrapper(func):
-        try: return func(rsrc)
-        finally: rsrc.close()
-    return wrapper
-
-def with_lock_file(path, exclusive = True):
-    """
-    Context manager for lock files.  Example:
-
-    @with_lock_file('/tmp/mylock')
-    def input():
-        print 'locked'
-        return raw_input()
-    # prints 'locked'
-    print input # prints what raw_input() returned
-    """
-    def wrapper(func):
-        @with_closing(file(path, 'w'))
-        def g(f):
-            if exclusive: locktype = LOCK_EX
-            else:         locktype = LOCK_SH
-            flock(f, locktype)
-            try: return func()
-            finally: flock(f, LOCK_UN)
-        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.

diff --git a/files/usr/share/python-support/sipb-xen-base/invirt/config.py b/files/usr/share/python-support/sipb-xen-base/invirt/config.py
index 8648c70..69cb899 100644 (file)
--- a/files/usr/share/python-support/sipb-xen-base/invirt/config.py
+++ b/files/usr/share/python-support/sipb-xen-base/invirt/config.py
@@ -1,11 +1,14 @@
+from __future__ import with_statement
+
 import json
 from invirt.common import *
 from os import rename
 from os.path import getmtime
+from contextlib import closing
 
 default_src_path   = '/etc/invirt/master.yaml'
 default_cache_path = '/var/lib/invirt/cache.json'
-lock_file          = '/var/lib/invirt/cache.lock'
+lock_path          = '/var/lib/invirt/cache.lock'
 
 def load(src_path = default_src_path,
          cache_path = default_cache_path,
@@ -53,8 +56,9 @@ def load(src_path = default_src_path,
         # (changing) version of the data (but the transaction can share the
         # lock with other concurrent reads).  This isolation is accomplished
         # using an atomic filesystem rename in the refreshing stage.
-        try: ns.cfg = with_closing(file(cache_path)) (
-                lambda f: json.read(f.read()))
+        try: 
+            with closing(file(cache_path)) as f:
+                ns.cfg = json.read(f.read())
         except: do_refresh = True
 
     if do_refresh:
@@ -68,17 +72,17 @@ def load(src_path = default_src_path,
         try:    loader = yaml.CSafeLoader
         except: loader = yaml.SafeLoader
         try:
-            @with_lock_file(lock_file)
-            def refresh_cache():
-                ns.cfg = with_closing(file(src_path)) (
-                        lambda f: yaml.load(f, loader))
-                try: with_closing(file(cache_path + '.tmp', 'w')) (
-                        lambda f: f.write(json.write(ns.cfg)))
+            with lock_file(lock_path):
+                with closing(file(src_path)) as f:
+                    ns.cfg = yaml.load(f, loader)
+                try: 
+                    with closing(file(cache_path + '.tmp', 'w')) as f:
+                        f.write(json.write(ns.cfg))
                 except: pass # silent failure
                 else: rename(cache_path + '.tmp', cache_path)
         except IOError:
-            ns.cfg = with_closing(file(src_path)) (
-                    lambda f: yaml.load(f, loader))
+            with closing(file(src_path)) as f:
+                ns.cfg = yaml.load(f, loader)
     return ns.cfg
 
 dicts = load()