Current File : //usr/lib/calibre/calibre/utils/shared_file.py
#!/usr/bin/env python3
__license__ = 'GPL v3'
__copyright__ = '2015, Kovid Goyal <kovid at kovidgoyal.net>'
import os, sys
from polyglot.builtins import reraise
from calibre.constants import iswindows
'''
This module defines a share_open() function which is a replacement for
python's builtin open() function.
This replacement, opens 'shareable' files on all platforms. That is files that
can be read from and written to and deleted at the same time by multiple
processes. All file handles are non-inheritable, as in Python 3, but unlike,
Python 2. Non-inheritance is atomic.
Caveats on windows: On windows sharing is co-operative, i.e. it only works if
all processes involved open the file with share_open(). Also while you can
delete a file that is open, you cannot open a new file with the same filename
until all open file handles are closed. You also cannot delete the containing
directory until all file handles are closed. To get around this, rename the
file before deleting it.
'''
if iswindows:
from numbers import Integral
import msvcrt
from calibre_extensions import winutil
_ACCESS_MASK = os.O_RDONLY | os.O_WRONLY | os.O_RDWR
_ACCESS_MAP = {
os.O_RDONLY : winutil.GENERIC_READ,
os.O_WRONLY : winutil.GENERIC_WRITE,
os.O_RDWR : winutil.GENERIC_READ | winutil.GENERIC_WRITE
}
_CREATE_MASK = os.O_CREAT | os.O_EXCL | os.O_TRUNC
_CREATE_MAP = {
0 : winutil.OPEN_EXISTING,
os.O_EXCL : winutil.OPEN_EXISTING,
os.O_CREAT : winutil.OPEN_ALWAYS,
os.O_CREAT | os.O_EXCL : winutil.CREATE_NEW,
os.O_CREAT | os.O_TRUNC | os.O_EXCL : winutil.CREATE_NEW,
os.O_TRUNC : winutil.TRUNCATE_EXISTING,
os.O_TRUNC | os.O_EXCL : winutil.TRUNCATE_EXISTING,
os.O_CREAT | os.O_TRUNC : winutil.CREATE_ALWAYS
}
def os_open(path, flags, mode=0o777, share_flags=winutil.FILE_SHARE_VALID_FLAGS):
'''
Replacement for os.open() allowing moving or unlinking before closing
'''
if not isinstance(flags, Integral):
raise TypeError('flags must be an integer')
if not isinstance(mode, Integral):
raise TypeError('mode must be an integer')
if share_flags & ~winutil.FILE_SHARE_VALID_FLAGS:
raise ValueError('bad share_flags: %r' % share_flags)
access_flags = _ACCESS_MAP[flags & _ACCESS_MASK]
create_flags = _CREATE_MAP[flags & _CREATE_MASK]
attrib_flags = winutil.FILE_ATTRIBUTE_NORMAL
if flags & os.O_CREAT and mode & ~0o444 == 0:
attrib_flags = winutil.FILE_ATTRIBUTE_READONLY
if flags & os.O_TEMPORARY:
share_flags |= winutil.FILE_SHARE_DELETE
attrib_flags |= winutil.FILE_FLAG_DELETE_ON_CLOSE
access_flags |= winutil.DELETE
if flags & os.O_SHORT_LIVED:
attrib_flags |= winutil.FILE_ATTRIBUTE_TEMPORARY
if flags & os.O_SEQUENTIAL:
attrib_flags |= winutil.FILE_FLAG_SEQUENTIAL_SCAN
if flags & os.O_RANDOM:
attrib_flags |= winutil.FILE_FLAG_RANDOM_ACCESS
h = winutil.create_file(
path, access_flags, share_flags, create_flags, attrib_flags)
ans = msvcrt.open_osfhandle(int(h), flags | os.O_NOINHERIT)
h.detach()
return ans
def share_open(*a, **kw):
kw['opener'] = os_open
return open(*a, **kw)
else:
share_open = open
def raise_winerror(x):
reraise(NotImplementedError, None, sys.exc_info()[2])
def find_tests():
import unittest
from calibre.ptempfile import TemporaryDirectory
class SharedFileTest(unittest.TestCase):
def test_shared_file(self):
eq = self.assertEqual
with TemporaryDirectory() as tdir:
fname = os.path.join(tdir, 'test.txt')
with share_open(fname, 'wb') as f:
f.write(b'a' * 20 * 1024)
eq(fname, f.name)
f = share_open(fname, 'rb')
eq(f.read(1), b'a')
if iswindows:
os.rename(fname, fname+'.moved')
os.remove(fname+'.moved')
else:
os.remove(fname)
eq(f.read(1), b'a')
f2 = share_open(fname, 'w+b')
f2.write(b'b' * 10 * 1024)
f2.seek(0)
eq(f.read(10000), b'a'*10000)
eq(f2.read(100), b'b' * 100)
f3 = share_open(fname, 'rb')
eq(f3.read(100), b'b' * 100)
return unittest.defaultTestLoader.loadTestsFromTestCase(SharedFileTest)
def run_tests():
from calibre.utils.run_tests import run_tests
run_tests(find_tests)
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