digits = "0123456789"
ascii_letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
-import re
+import re, fcntl, os
def explode_version(s):
r = []
constants = tuple(constants)
EnumType = EnumClass()
return EnumType
+
+def lockfile(name):
+ """
+ Use the file fn as a lock file, return when the lock has been aquired.
+ Returns a variable to pass to unlockfile().
+ """
+ while True:
+ # If we leave the lockfiles lying around there is no problem
+ # but we should clean up after ourselves. This gives potential
+ # for races though. To work around this, when we aquire the lock
+ # we check the file we locked was still the lock file on disk.
+ # by comparing inode numbers. If they don't match or the lockfile
+ # no longer exists, we start again.
+
+ # This implementation is unfair since the last person to request the
+ # lock is the most likely to win it.
+
+ lf = open(name, "a+")
+ fcntl.flock(lf.fileno(), fcntl.LOCK_EX)
+ statinfo = os.fstat(lf.fileno())
+ if os.path.exists(lf.name):
+ statinfo2 = os.stat(lf.name)
+ if statinfo.st_ino == statinfo2.st_ino:
+ return lf
+ # File no longer exists or changed, retry
+ lf.close
+
+def unlockfile(lf):
+ """
+ Unlock a file locked using lockfile()
+ """
+ os.unlink(lf.name)
+ fcntl.flock(lf.fileno(), fcntl.LOCK_UN)
+ lf.close
+
