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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 codecs
import errno
import os
import socket
import sys
from warnings import warn
from bzrlib.osutils import rename
# not forksafe - but we dont fork.
_pid = os.getpid()
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.
"""
__slots__ = ['f', 'tmpfilename', 'realfilename', 'write']
def __init__(self, filename, mode='wb', new_mode=0666):
self.f = None
assert mode in ('wb', 'wt'), \
"invalid AtomicFile mode %r" % mode
# old version:
#self.tmpfilename = '%s.%d.%s.tmp' % (filename, os.getpid(),
# socket.gethostname())
# new version:
# This is 'broken' on NFS: it wmay collide with another NFS client.
# however, we use this to write files within a directory that we have
# locked, so it being racy on NFS is not a concern. The only other
# files we use this for are .bzr.ignore, which can race anyhow.
self.tmpfilename = '%s.%d.tmp' % (filename, _pid)
self.realfilename = filename
# Use a low level fd operation to avoid chmodding later.
fd = os.open(self.tmpfilename, os.O_EXCL | os.O_CREAT | os.O_WRONLY,
new_mode)
# open a normal python file to get the text vs binary support needed
# for windows.
try:
self.f = os.fdopen(fd, mode)
except:
os.close(fd)
raise
self.write = self.f.write
def __repr__(self):
return '%s(%r)' % (self.__class__.__name__,
self.realfilename)
def commit(self):
"""Close the file and move to final name."""
if self.f is None:
raise Exception('%r is already closed' % self)
f = self.f
self.f = None
f.close()
rename(self.tmpfilename, self.realfilename)
def abort(self):
"""Discard temporary file without committing changes."""
if self.f is None:
raise Exception('%r is already closed' % self)
f = self.f
self.f = None
f.close()
os.remove(self.tmpfilename)
def close(self):
"""Discard the file unless already committed."""
if self.f is not None:
self.abort()
def __del__(self):
if self.f is not None:
warn("%r leaked" % self)
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