[Python-checkins] cpython (2.7): #9559: Append data to single-file mailbox files if messages are only added

Thu Jun 28 12:59:02 CEST 2012

http://hg.python.org/cpython/rev/c37cb11b546f
changeset: 77832:c37cb11b546f
branch: 2.7
parent: 77823:73710ae9fedc
user: Petri Lehtinen <petri at digip.org>
date: Thu Jun 28 13:48:17 2012 +0300
summary:
 #9559: Append data to single-file mailbox files if messages are only added
If messages were only added, a new file is no longer created and
renamed over the old file when flush() is called on an mbox, MMDF or
Babyl mailbox.
files:
 Lib/mailbox.py | 18 ++++++++++++++--
 Lib/test/test_mailbox.py | 29 ++++++++++++++++++++++++++-
 Misc/NEWS | 4 +++
 3 files changed, 46 insertions(+), 5 deletions(-)

diff --git a/Lib/mailbox.py b/Lib/mailbox.py
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -561,16 +561,19 @@
 self._file = f
 self._toc = None
 self._next_key = 0
- self._pending = False # No changes require rewriting the file.
+ self._pending = False # No changes require rewriting the file.
+ self._pending_sync = False # No need to sync the file
 self._locked = False
- self._file_length = None # Used to record mailbox size
+ self._file_length = None # Used to record mailbox size
 
 def add(self, message):
 """Add message and return assigned key."""
 self._lookup()
 self._toc[self._next_key] = self._append_message(message)
 self._next_key += 1
- self._pending = True
+ # _append_message appends the message to the mailbox file. We
+ # don't need a full rewrite + rename, sync is enough.
+ self._pending_sync = True
 return self._next_key - 1
 
 def remove(self, key):
@@ -616,6 +619,11 @@
 def flush(self):
 """Write any pending changes to disk."""
 if not self._pending:
+ if self._pending_sync:
+ # Messages have only been added, so syncing the file
+ # is enough.
+ _sync_flush(self._file)
+ self._pending_sync = False
 return
 
 # In order to be writing anything out at all, self._toc must
@@ -669,6 +677,7 @@
 self._file = open(self._path, 'rb+')
 self._toc = new_toc
 self._pending = False
+ self._pending_sync = False
 if self._locked:
 _lock_file(self._file, dotlock=False)
 
@@ -705,6 +714,9 @@
 """Append message to mailbox and return (start, stop) offsets."""
 self._file.seek(0, 2)
 before = self._file.tell()
+ if len(self._toc) == 0:
+ # This is the first message
+ self._pre_mailbox_hook(self._file)
 try:
 self._pre_message_hook(self._file)
 offsets = self._install_message(message)
diff --git a/Lib/test/test_mailbox.py b/Lib/test/test_mailbox.py
--- a/Lib/test/test_mailbox.py
+++ b/Lib/test/test_mailbox.py
@@ -824,7 +824,32 @@
 self._box._refresh()
 self.assertTrue(refreshed())
 
-class _TestMboxMMDF(TestMailbox):
+
+class _TestSingleFile(TestMailbox):
+ '''Common tests for single-file mailboxes'''
+
+ def test_add_doesnt_rewrite(self):
+ # When only adding messages, flush() should not rewrite the
+ # mailbox file. See issue #9559.
+
+ # Inode number changes if the contents are written to another
+ # file which is then renamed over the original file. So we
+ # must check that the inode number doesn't change.
+ inode_before = os.stat(self._path).st_ino
+
+ self._box.add(self._template % 0)
+ self._box.flush()
+
+ inode_after = os.stat(self._path).st_ino
+ self.assertEqual(inode_before, inode_after)
+
+ # Make sure the message was really added
+ self._box.close()
+ self._box = self._factory(self._path)
+ self.assertEqual(len(self._box), 1)
+
+
+class _TestMboxMMDF(_TestSingleFile):
 
 def tearDown(self):
 self._box.close()
@@ -1085,7 +1110,7 @@
 return os.path.join(self._path, '.mh_sequences.lock')
 
 
-class TestBabyl(TestMailbox, unittest.TestCase):
+class TestBabyl(_TestSingleFile, unittest.TestCase):
 
 _factory = lambda self, path, factory=None: mailbox.Babyl(path, factory)
 
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -75,6 +75,10 @@
 Library
 -------
 
+- Issue #9559: If messages were only added, a new file is no longer
+ created and renamed over the old file when flush() is called on an
+ mbox, MMDF or Babyl mailbox.
+
 - Issue #14653: email.utils.mktime_tz() no longer relies on system
 mktime() when timezone offest is supplied.
 
-- 
Repository URL: http://hg.python.org/cpython
