227 lines
6.6 KiB
Python
227 lines
6.6 KiB
Python
import contextlib
|
|
import io
|
|
import os
|
|
import sys
|
|
import tempfile
|
|
|
|
try:
|
|
import fcntl
|
|
except ImportError:
|
|
fcntl = None
|
|
|
|
# `fspath` was added in Python 3.6
|
|
try:
|
|
from os import fspath
|
|
except ImportError:
|
|
fspath = None
|
|
|
|
__version__ = '1.4.0'
|
|
|
|
|
|
PY2 = sys.version_info[0] == 2
|
|
|
|
text_type = unicode if PY2 else str # noqa
|
|
|
|
|
|
def _path_to_unicode(x):
|
|
if not isinstance(x, text_type):
|
|
return x.decode(sys.getfilesystemencoding())
|
|
return x
|
|
|
|
|
|
DEFAULT_MODE = "wb" if PY2 else "w"
|
|
|
|
|
|
_proper_fsync = os.fsync
|
|
|
|
|
|
if sys.platform != 'win32':
|
|
if hasattr(fcntl, 'F_FULLFSYNC'):
|
|
def _proper_fsync(fd):
|
|
# https://lists.apple.com/archives/darwin-dev/2005/Feb/msg00072.html
|
|
# https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man2/fsync.2.html
|
|
# https://github.com/untitaker/python-atomicwrites/issues/6
|
|
fcntl.fcntl(fd, fcntl.F_FULLFSYNC)
|
|
|
|
def _sync_directory(directory):
|
|
# Ensure that filenames are written to disk
|
|
fd = os.open(directory, 0)
|
|
try:
|
|
_proper_fsync(fd)
|
|
finally:
|
|
os.close(fd)
|
|
|
|
def _replace_atomic(src, dst):
|
|
os.rename(src, dst)
|
|
_sync_directory(os.path.normpath(os.path.dirname(dst)))
|
|
|
|
def _move_atomic(src, dst):
|
|
os.link(src, dst)
|
|
os.unlink(src)
|
|
|
|
src_dir = os.path.normpath(os.path.dirname(src))
|
|
dst_dir = os.path.normpath(os.path.dirname(dst))
|
|
_sync_directory(dst_dir)
|
|
if src_dir != dst_dir:
|
|
_sync_directory(src_dir)
|
|
else:
|
|
from ctypes import windll, WinError
|
|
|
|
_MOVEFILE_REPLACE_EXISTING = 0x1
|
|
_MOVEFILE_WRITE_THROUGH = 0x8
|
|
_windows_default_flags = _MOVEFILE_WRITE_THROUGH
|
|
|
|
def _handle_errors(rv):
|
|
if not rv:
|
|
raise WinError()
|
|
|
|
def _replace_atomic(src, dst):
|
|
_handle_errors(windll.kernel32.MoveFileExW(
|
|
_path_to_unicode(src), _path_to_unicode(dst),
|
|
_windows_default_flags | _MOVEFILE_REPLACE_EXISTING
|
|
))
|
|
|
|
def _move_atomic(src, dst):
|
|
_handle_errors(windll.kernel32.MoveFileExW(
|
|
_path_to_unicode(src), _path_to_unicode(dst),
|
|
_windows_default_flags
|
|
))
|
|
|
|
|
|
def replace_atomic(src, dst):
|
|
'''
|
|
Move ``src`` to ``dst``. If ``dst`` exists, it will be silently
|
|
overwritten.
|
|
|
|
Both paths must reside on the same filesystem for the operation to be
|
|
atomic.
|
|
'''
|
|
return _replace_atomic(src, dst)
|
|
|
|
|
|
def move_atomic(src, dst):
|
|
'''
|
|
Move ``src`` to ``dst``. There might a timewindow where both filesystem
|
|
entries exist. If ``dst`` already exists, :py:exc:`FileExistsError` will be
|
|
raised.
|
|
|
|
Both paths must reside on the same filesystem for the operation to be
|
|
atomic.
|
|
'''
|
|
return _move_atomic(src, dst)
|
|
|
|
|
|
class AtomicWriter(object):
|
|
'''
|
|
A helper class for performing atomic writes. Usage::
|
|
|
|
with AtomicWriter(path).open() as f:
|
|
f.write(...)
|
|
|
|
:param path: The destination filepath. May or may not exist.
|
|
:param mode: The filemode for the temporary file. This defaults to `wb` in
|
|
Python 2 and `w` in Python 3.
|
|
:param overwrite: If set to false, an error is raised if ``path`` exists.
|
|
Errors are only raised after the file has been written to. Either way,
|
|
the operation is atomic.
|
|
|
|
If you need further control over the exact behavior, you are encouraged to
|
|
subclass.
|
|
'''
|
|
|
|
def __init__(self, path, mode=DEFAULT_MODE, overwrite=False,
|
|
**open_kwargs):
|
|
if 'a' in mode:
|
|
raise ValueError(
|
|
'Appending to an existing file is not supported, because that '
|
|
'would involve an expensive `copy`-operation to a temporary '
|
|
'file. Open the file in normal `w`-mode and copy explicitly '
|
|
'if that\'s what you\'re after.'
|
|
)
|
|
if 'x' in mode:
|
|
raise ValueError('Use the `overwrite`-parameter instead.')
|
|
if 'w' not in mode:
|
|
raise ValueError('AtomicWriters can only be written to.')
|
|
|
|
# Attempt to convert `path` to `str` or `bytes`
|
|
if fspath is not None:
|
|
path = fspath(path)
|
|
|
|
self._path = path
|
|
self._mode = mode
|
|
self._overwrite = overwrite
|
|
self._open_kwargs = open_kwargs
|
|
|
|
def open(self):
|
|
'''
|
|
Open the temporary file.
|
|
'''
|
|
return self._open(self.get_fileobject)
|
|
|
|
@contextlib.contextmanager
|
|
def _open(self, get_fileobject):
|
|
f = None # make sure f exists even if get_fileobject() fails
|
|
try:
|
|
success = False
|
|
with get_fileobject(**self._open_kwargs) as f:
|
|
yield f
|
|
self.sync(f)
|
|
self.commit(f)
|
|
success = True
|
|
finally:
|
|
if not success:
|
|
try:
|
|
self.rollback(f)
|
|
except Exception:
|
|
pass
|
|
|
|
def get_fileobject(self, suffix="", prefix=tempfile.gettempprefix(),
|
|
dir=None, **kwargs):
|
|
'''Return the temporary file to use.'''
|
|
if dir is None:
|
|
dir = os.path.normpath(os.path.dirname(self._path))
|
|
descriptor, name = tempfile.mkstemp(suffix=suffix, prefix=prefix,
|
|
dir=dir)
|
|
# io.open() will take either the descriptor or the name, but we need
|
|
# the name later for commit()/replace_atomic() and couldn't find a way
|
|
# to get the filename from the descriptor.
|
|
os.close(descriptor)
|
|
kwargs['mode'] = self._mode
|
|
kwargs['file'] = name
|
|
return io.open(**kwargs)
|
|
|
|
def sync(self, f):
|
|
'''responsible for clearing as many file caches as possible before
|
|
commit'''
|
|
f.flush()
|
|
_proper_fsync(f.fileno())
|
|
|
|
def commit(self, f):
|
|
'''Move the temporary file to the target location.'''
|
|
if self._overwrite:
|
|
replace_atomic(f.name, self._path)
|
|
else:
|
|
move_atomic(f.name, self._path)
|
|
|
|
def rollback(self, f):
|
|
'''Clean up all temporary resources.'''
|
|
os.unlink(f.name)
|
|
|
|
|
|
def atomic_write(path, writer_cls=AtomicWriter, **cls_kwargs):
|
|
'''
|
|
Simple atomic writes. This wraps :py:class:`AtomicWriter`::
|
|
|
|
with atomic_write(path) as f:
|
|
f.write(...)
|
|
|
|
:param path: The target path to write to.
|
|
:param writer_cls: The writer class to use. This parameter is useful if you
|
|
subclassed :py:class:`AtomicWriter` to change some behavior and want to
|
|
use that new subclass.
|
|
|
|
Additional keyword arguments are passed to the writer class. See
|
|
:py:class:`AtomicWriter`.
|
|
'''
|
|
return writer_cls(path, **cls_kwargs).open()
|