tests: implement a basic system-wide lock

It will be used to allocate ports in a safer way.

git-svn-id: https://svn.erp5.org/repos/neo/trunk@2664 71dcc9de-d417-0410-9af5-da40c76e7ee4

neo/tests/__init__.py

@@ -15,6 +15,7 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 
+import errno
 import os
 import random
 import socket
@@ -28,7 +29,7 @@ from mock import Mock
 from neo.lib import protocol
 from neo.lib.protocol import Packets
 from neo.lib.util import getAddressType
-from time import time, gmtime
+from time import time, gmtime, sleep
 from struct import pack, unpack
 
 DB_PREFIX = os.getenv('NEO_DB_PREFIX', 'test_neo_')
@@ -455,3 +456,41 @@ class DoNothingConnector(Mock):
     def getDescriptor(self):
         return self.desc
 
+class SocketLock(object):
+    """Basic system-wide lock"""
+
+    _socket = None
+
+    def __init__(self, address, family=socket.AF_UNIX, type=socket.SOCK_DGRAM):
+        if family == socket.AF_UNIX:
+            address = '\0' + address
+        self.address = address
+        self.socket_args = family, type
+
+    def locked(self):
+        return self._socket is not None
+
+    def acquire(self, blocking=1):
+        assert self._socket is None
+        s = socket.socket(*self.socket_args)
+        try:
+            while True:
+                try:
+                    s.bind(self.address)
+                except socket.error, e:
+                    if e[0] != errno.EADDRINUSE:
+                        raise
+                    if not blocking:
+                        return False
+                    sleep(1)
+                else:
+                    self._socket = s
+                    return True
+        finally:
+          if self._socket is None:
+              s.close()
+
+    def release(self):
+        s = self._socket
+        del self._socket
+        s.close()