"""
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 django.core.files import locks
try:
from shutil import copystat
except ImportError:
import stat
def copystat(src, dst):
"""Copy all stat info (mode bits, atime and mtime) from src to dst"""
st = os.stat(src)
mode = stat.S_IMODE(st.st_mode)
if hasattr(os, 'utime'):
os.utime(dst, (st.st_atime, st.st_mtime))
if hasattr(os, 'chmod'):
os.chmod(dst, mode)
__all__ = ['file_move_safe']
def _samefile(src, dst):
# Macintosh, Unix.
if hasattr(os.path,'samefile'):
try:
return os.path.samefile(src, dst)
except OSError:
return False
# All other platforms: check for same pathname.
return (os.path.normcase(os.path.abspath(src)) ==
os.path.normcase(os.path.abspath(dst)))
def file_move_safe(old_file_name, new_file_name, chunk_size = 1024*64, allow_overwrite=False):
"""
Moves a file from one location to another in the safest way possible.
First, tries ``os.rename``, which is simple but will break across filesystems.
If that fails, streams manually from one file to another in pure Python.
If the destination file exists and ``allow_overwrite`` is ``False``, this
function will throw an ``IOError``.
"""
# There's no reason to move if we don't have to.
if _samefile(old_file_name, new_file_name):
return
try:
os.rename(old_file_name, new_file_name)
return
except OSError:
# This will happen 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
old_file = open(old_file_name, 'rb')
try:
# 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) |
(not allow_overwrite and os.O_EXCL or 0))
try:
locks.lock(fd, locks.LOCK_EX)
current_chunk = None
while current_chunk != '':
current_chunk = old_file.read(chunk_size)
os.write(fd, current_chunk)
finally:
locks.unlock(fd)
os.close(fd)
finally:
old_file.close()
copystat(old_file_name, new_file_name)
try:
os.remove(old_file_name)
except OSError, 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 and getattr(e, 'errno', 0) != 13:
raise
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