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Mini Shell
Mini Shell
# -*- coding: utf-8 -*-
'''
A module written originally by Armin Ronacher to manage file transfers in an
atomic way
'''
# Import python libs
from __future__ import absolute_import, print_function, unicode_literals
import os
import tempfile
import sys
import errno
import time
import random
import shutil
from salt.ext import six
# Import salt libs
import salt.utils.win_dacl
CAN_RENAME_OPEN_FILE = False
if os.name == 'nt': # pragma: no cover
_rename = lambda src, dst: False # pylint: disable=C0103
_rename_atomic = lambda src, dst: False # pylint: disable=C0103
try:
import ctypes
_MOVEFILE_REPLACE_EXISTING = 0x1
_MOVEFILE_WRITE_THROUGH = 0x8
_MoveFileEx = ctypes.windll.kernel32.MoveFileExW # pylint: disable=C0103
def _rename(src, dst): # pylint: disable=E0102
if not isinstance(src, six.text_type):
src = six.text_type(src, sys.getfilesystemencoding())
if not isinstance(dst, six.text_type):
dst = six.text_type(dst, sys.getfilesystemencoding())
if _rename_atomic(src, dst):
return True
retry = 0
rval = False
while not rval and retry < 100:
rval = _MoveFileEx(src, dst, _MOVEFILE_REPLACE_EXISTING |
_MOVEFILE_WRITE_THROUGH)
if not rval:
time.sleep(0.001)
retry += 1
return rval
# new in Vista and Windows Server 2008
# pylint: disable=C0103
_CreateTransaction = ctypes.windll.ktmw32.CreateTransaction
_CommitTransaction = ctypes.windll.ktmw32.CommitTransaction
_MoveFileTransacted = ctypes.windll.kernel32.MoveFileTransactedW
_CloseHandle = ctypes.windll.kernel32.CloseHandle
# pylint: enable=C0103
CAN_RENAME_OPEN_FILE = True
def _rename_atomic(src, dst): # pylint: disable=E0102
tra = _CreateTransaction(None, 0, 0, 0, 0, 1000, 'Atomic rename')
if tra == -1:
return False
try:
retry = 0
rval = False
while not rval and retry < 100:
rval = _MoveFileTransacted(src, dst, None, None,
_MOVEFILE_REPLACE_EXISTING |
_MOVEFILE_WRITE_THROUGH, tra)
if rval:
rval = _CommitTransaction(tra)
break
else:
time.sleep(0.001)
retry += 1
return rval
finally:
_CloseHandle(tra)
except Exception:
pass
def atomic_rename(src, dst):
# Try atomic or pseudo-atomic rename
if _rename(src, dst):
return
# Fall back to "move away and replace"
try:
os.rename(src, dst)
except OSError as err:
if err.errno != errno.EEXIST:
raise
old = '{0}-{1:08x}'.format(dst, random.randint(0, sys.maxint))
os.rename(dst, old)
os.rename(src, dst)
try:
os.unlink(old)
except Exception:
pass
else:
atomic_rename = os.rename # pylint: disable=C0103
CAN_RENAME_OPEN_FILE = True
class _AtomicWFile(object):
'''
Helper class for :func:`atomic_open`.
'''
def __init__(self, fhanle, tmp_filename, filename):
self._fh = fhanle
self._tmp_filename = tmp_filename
self._filename = filename
def __getattr__(self, attr):
return getattr(self._fh, attr)
def __enter__(self):
return self
def close(self):
if self._fh.closed:
return
self._fh.close()
if os.path.isfile(self._filename):
if salt.utils.win_dacl.HAS_WIN32:
salt.utils.win_dacl.copy_security(
source=self._filename, target=self._tmp_filename)
else:
shutil.copymode(self._filename, self._tmp_filename)
st = os.stat(self._filename)
os.chown(self._tmp_filename, st.st_uid, st.st_gid)
atomic_rename(self._tmp_filename, self._filename)
def __exit__(self, exc_type, exc_value, traceback):
if exc_type is None:
self.close()
else:
self._fh.close()
try:
os.remove(self._tmp_filename)
except OSError:
pass
def __repr__(self):
return '<{0} {1}{2}, mode {3}>'.format(
self.__class__.__name__,
self._fh.closed and 'closed ' or '',
self._filename,
self._fh.mode
)
def atomic_open(filename, mode='w'):
'''
Works like a regular `open()` but writes updates into a temporary
file instead of the given file and moves it over when the file is
closed. The file returned behaves as if it was a regular Python
'''
if mode in ('r', 'rb', 'r+', 'rb+', 'a', 'ab'):
raise TypeError('Read or append modes don\'t work with atomic_open')
kwargs = {
'prefix': '.___atomic_write',
'dir': os.path.dirname(filename),
'delete': False,
}
if six.PY3 and 'b' not in mode:
kwargs['newline'] = ''
ntf = tempfile.NamedTemporaryFile(mode, **kwargs)
return _AtomicWFile(ntf, ntf.name, filename)
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