mercurial/dirstateguard.py

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mercurial/dirstateguard.py	Mon Nov 21 21:29:32 2016 -0500
@@ -0,0 +1,69 @@
+# dirstateguard.py - class to allow restoring dirstate after failure
+#
+# Copyright 2005-2007 Matt Mackall <[e-mail]>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from __future__ import absolute_import
+
+from .i18n import _
+
+from . import (
+    error,
+)
+
+class dirstateguard(object):
+    '''Restore dirstate at unexpected failure.
+
+    At the construction, this class does:
+
+    - write current ``repo.dirstate`` out, and
+    - save ``.hg/dirstate`` into the backup file
+
+    This restores ``.hg/dirstate`` from backup file, if ``release()``
+    is invoked before ``close()``.
+
+    This just removes the backup file at ``close()`` before ``release()``.
+    '''
+
+    def __init__(self, repo, name):
+        self._repo = repo
+        self._active = False
+        self._closed = False
+        self._suffix = '.backup.%s.%d' % (name, id(self))
+        repo.dirstate.savebackup(repo.currenttransaction(), self._suffix)
+        self._active = True
+
+    def __del__(self):
+        if self._active: # still active
+            # this may occur, even if this class is used correctly:
+            # for example, releasing other resources like transaction
+            # may raise exception before ``dirstateguard.release`` in
+            # ``release(tr, ....)``.
+            self._abort()
+
+    def close(self):
+        if not self._active: # already inactivated
+            msg = (_("can't close already inactivated backup: dirstate%s")
+                   % self._suffix)
+            raise error.Abort(msg)
+
+        self._repo.dirstate.clearbackup(self._repo.currenttransaction(),
+                                         self._suffix)
+        self._active = False
+        self._closed = True
+
+    def _abort(self):
+        self._repo.dirstate.restorebackup(self._repo.currenttransaction(),
+                                           self._suffix)
+        self._active = False
+
+    def release(self):
+        if not self._closed:
+            if not self._active: # already inactivated
+                msg = (_("can't release already inactivated backup:"
+                         " dirstate%s")
+                       % self._suffix)
+                raise error.Abort(msg)
+            self._abort()