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# Copyright (C) 2004, 2005 by 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
import errno
import os
from warnings import warn
from bzrlib.osutils import rename
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.
An encoding can be specified; otherwise the default is ascii.
"""
def __init__(self, filename, mode='wb', encoding=None, new_mode=None):
if mode != 'wb' and mode != 'wt':
raise ValueError("invalid AtomicFile mode %r" % mode)
import socket
self.tmpfilename = '%s.%d.%s.tmp' % (filename, os.getpid(),
socket.gethostname())
self.realfilename = filename
if encoding:
import codecs
self.f = codecs.open(self.tmpfilename, mode, encoding)
else:
self.f = open(self.tmpfilename, mode)
self.write = self.f.write
self.closed = False
self._new_mode = new_mode
def __repr__(self):
return '%s(%r)' % (self.__class__.__name__,
self.realfilename)
def commit(self):
"""Close the file and move to final name."""
if self.closed:
raise Exception('%r is already closed' % self)
self.closed = True
self.f.close()
self.f = None
try:
if self._new_mode is None:
self._new_mode = os.lstat(self.realfilename).st_mode
except OSError, e:
if e.errno != errno.ENOENT:
raise
else:
os.chmod(self.tmpfilename, self._new_mode)
rename(self.tmpfilename, self.realfilename)
def abort(self):
"""Discard temporary file without committing changes."""
if self.closed:
raise Exception('%r is already closed' % self)
self.closed = True
self.f.close()
self.f = None
os.remove(self.tmpfilename)
def close(self):
"""Discard the file unless already committed."""
if not self.closed:
self.abort()
def __del__(self):
if hasattr(self, 'closed') and not self.closed:
warn("%r leaked" % self)
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