diff lockfile-0.10.2/lockfile/linklockfile.py @ 33:7ceb967147c3

start xena with no gui add library files

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lockfile-0.10.2/lockfile/linklockfile.py	Wed Jul 22 13:24:44 2015 -0700
@@ -0,0 +1,73 @@
+from __future__ import absolute_import
+
+import time
+import os
+
+from . import (LockBase, LockFailed, NotLocked, NotMyLock, LockTimeout,
+               AlreadyLocked)
+
+class LinkLockFile(LockBase):
+    """Lock access to a file using atomic property of link(2).
+
+    >>> lock = LinkLockFile('somefile')
+    >>> lock = LinkLockFile('somefile', threaded=False)
+    """
+
+    def acquire(self, timeout=None):
+        try:
+            open(self.unique_name, "wb").close()
+        except IOError:
+            raise LockFailed("failed to create %s" % self.unique_name)
+
+        timeout = timeout is not None and timeout or self.timeout
+        end_time = time.time()
+        if timeout is not None and timeout > 0:
+            end_time += timeout
+
+        while True:
+            # Try and create a hard link to it.
+            try:
+                os.link(self.unique_name, self.lock_file)
+            except OSError:
+                # Link creation failed.  Maybe we've double-locked?
+                nlinks = os.stat(self.unique_name).st_nlink
+                if nlinks == 2:
+                    # The original link plus the one I created == 2.  We're
+                    # good to go.
+                    return
+                else:
+                    # Otherwise the lock creation failed.
+                    if timeout is not None and time.time() > end_time:
+                        os.unlink(self.unique_name)
+                        if timeout > 0:
+                            raise LockTimeout("Timeout waiting to acquire"
+                                              " lock for %s" %
+                                              self.path)
+                        else:
+                            raise AlreadyLocked("%s is already locked" %
+                                                self.path)
+                    time.sleep(timeout is not None and timeout/10 or 0.1)
+            else:
+                # Link creation succeeded.  We're good to go.
+                return
+
+    def release(self):
+        if not self.is_locked():
+            raise NotLocked("%s is not locked" % self.path)
+        elif not os.path.exists(self.unique_name):
+            raise NotMyLock("%s is locked, but not by me" % self.path)
+        os.unlink(self.unique_name)
+        os.unlink(self.lock_file)
+
+    def is_locked(self):
+        return os.path.exists(self.lock_file)
+
+    def i_am_locking(self):
+        return (self.is_locked() and
+                os.path.exists(self.unique_name) and
+                os.stat(self.unique_name).st_nlink == 2)
+
+    def break_lock(self):
+        if os.path.exists(self.lock_file):
+            os.unlink(self.lock_file)
+