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|
"""
Move a file in the safest way possible::
>>> from django.core.files.move import file_move_safe
>>> file_move_safe("/tmp/old_file", "/tmp/new_file")
"""
import os
from shutil import copymode, copystat
from django.core.files import locks
__all__ = ["file_move_safe"]
def file_move_safe(
old_file_name, new_file_name, chunk_size=1024 * 64, allow_overwrite=False
):
"""
Move a file from one location to another in the safest way possible.
First, try ``os.rename``, which is simple but will break across filesystems.
If that fails, stream manually from one file to another in pure Python.
If the destination file exists and ``allow_overwrite`` is ``False``, raise
``FileExistsError``.
"""
# There's no reason to move if we don't have to.
try:
if os.path.samefile(old_file_name, new_file_name):
return
except OSError:
pass
if not allow_overwrite and os.access(new_file_name, os.F_OK):
raise FileExistsError(
f"Destination file {new_file_name} exists and allow_overwrite is False."
)
try:
os.rename(old_file_name, new_file_name)
return
except OSError:
# OSError happens with os.rename() if moving to another filesystem or
# when moving opened files on certain operating systems.
pass
# first open the old file, so that it won't go away
with open(old_file_name, "rb") as old_file:
# now open the new file, not forgetting allow_overwrite
fd = os.open(
new_file_name,
(
os.O_WRONLY
| os.O_CREAT
| getattr(os, "O_BINARY", 0)
| (os.O_EXCL if not allow_overwrite else 0)
| os.O_TRUNC
),
)
try:
locks.lock(fd, locks.LOCK_EX)
current_chunk = None
while current_chunk != b"":
current_chunk = old_file.read(chunk_size)
os.write(fd, current_chunk)
finally:
locks.unlock(fd)
os.close(fd)
try:
copystat(old_file_name, new_file_name)
except PermissionError:
# Certain filesystems (e.g. CIFS) fail to copy the file's metadata if
# the type of the destination filesystem isn't the same as the source
# filesystem. This also happens with some SELinux-enabled systems.
# Ignore that, but try to set basic permissions.
try:
copymode(old_file_name, new_file_name)
except PermissionError:
pass
try:
os.remove(old_file_name)
except PermissionError as e:
# Certain operating systems (Cygwin and Windows)
# fail when deleting opened files, ignore it. (For the
# systems where this happens, temporary files will be auto-deleted
# on close anyway.)
if getattr(e, "winerror", 0) != 32:
raise
|
