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# Copyright (C) 2005, 2006, 2008, 2009, 2010 Canonical Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
from __future__ import absolute_import
import os
from bzrlib.lazy_import import lazy_import
lazy_import(globals(), """
import stat
import warnings
from bzrlib import (
errors,
osutils,
symbol_versioning,
)
""")
# not forksafe - but we dont fork.
_pid = os.getpid()
_hostname = None
class AtomicFile(object):
"""A file that does an atomic-rename to move into place.
This also causes hardlinks to break when it's written out.
Open this as for a regular file, then use commit() to move into
place or abort() to cancel.
"""
__slots__ = ['tmpfilename', 'realfilename', '_fd']
def __init__(self, filename, mode='wb', new_mode=None):
global _hostname
self._fd = None
if _hostname is None:
_hostname = osutils.get_host_name()
self.tmpfilename = '%s.%d.%s.%s.tmp' % (filename, _pid, _hostname,
osutils.rand_chars(10))
self.realfilename = filename
flags = os.O_EXCL | os.O_CREAT | os.O_WRONLY | osutils.O_NOINHERIT
if mode == 'wb':
flags |= osutils.O_BINARY
elif mode != 'wt':
raise ValueError("invalid AtomicFile mode %r" % mode)
if new_mode is not None:
local_mode = new_mode
else:
local_mode = 0666
# Use a low level fd operation to avoid chmodding later.
# This may not succeed, but it should help most of the time
self._fd = os.open(self.tmpfilename, flags, local_mode)
if new_mode is not None:
# Because of umask issues, we may need to chmod anyway
# the common case is that we won't, though.
st = os.fstat(self._fd)
if stat.S_IMODE(st.st_mode) != new_mode:
osutils.chmod_if_possible(self.tmpfilename, new_mode)
def __repr__(self):
return '%s(%r)' % (self.__class__.__name__,
self.realfilename)
def write(self, data):
"""Write some data to the file. Like file.write()"""
os.write(self._fd, data)
def _close_tmpfile(self, func_name):
"""Close the local temp file in preparation for commit or abort"""
if self._fd is None:
raise errors.AtomicFileAlreadyClosed(path=self.realfilename,
function=func_name)
fd = self._fd
self._fd = None
os.close(fd)
def commit(self):
"""Close the file and move to final name."""
self._close_tmpfile('commit')
osutils.rename(self.tmpfilename, self.realfilename)
def abort(self):
"""Discard temporary file without committing changes."""
self._close_tmpfile('abort')
os.remove(self.tmpfilename)
def close(self):
"""Discard the file unless already committed."""
if self._fd is not None:
self.abort()
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