Python os.O_NOINHERIT Examples

def writef_win32(f,data,m='w',encoding='ISO8859-1'):
	if sys.hexversion>0x3000000 and not'b'in m:
		data=data.encode(encoding)
		m+='b'
	flags=os.O_CREAT|os.O_TRUNC|os.O_WRONLY|os.O_NOINHERIT
	if'b'in m:
		flags|=os.O_BINARY
	if'+'in m:
		flags|=os.O_RDWR
	try:
		fd=os.open(f,flags)
	except OSError:
		raise IOError('Cannot write to %r'%f)
	f=os.fdopen(fd,m)
	try:
		f.write(data)
	finally:
		f.close() 

def writef_win32(f,data,m='w',encoding='ISO8859-1'):
	if sys.hexversion>0x3000000 and not'b'in m:
		data=data.encode(encoding)
		m+='b'
	flags=os.O_CREAT|os.O_TRUNC|os.O_WRONLY|os.O_NOINHERIT
	if'b'in m:
		flags|=os.O_BINARY
	if'+'in m:
		flags|=os.O_RDWR
	try:
		fd=os.open(f,flags)
	except OSError:
		raise IOError('Cannot write to %r'%f)
	f=os.fdopen(fd,m)
	try:
		f.write(data)
	finally:
		f.close() 

def shared_open(path):
    """Opens a file with full sharing mode and without inheritance.

    The file is open for both read and write.

    See https://bugs.python.org/issue15244 for inspiration.
    """
    path = six.text_type(path)
    handle = ctypes.windll.kernel32.CreateFileW(
        path,
        GENERIC_READ|GENERIC_WRITE,
        FILE_SHARE_READ|FILE_SHARE_WRITE|FILE_SHARE_DELETE,
        None,
        OPEN_ALWAYS,
        FILE_ATTRIBUTE_NORMAL,
        None)
    ctr_handle = msvcrt.open_osfhandle(handle, os.O_BINARY | os.O_NOINHERIT)
    return os.fdopen(ctr_handle, 'r+b') 

def readf_win32(f,m='r',encoding='ISO8859-1'):
	flags=os.O_NOINHERIT|os.O_RDONLY
	if'b'in m:
		flags|=os.O_BINARY
	if'+'in m:
		flags|=os.O_RDWR
	try:
		fd=os.open(f,flags)
	except OSError:
		raise IOError('Cannot read from %r'%f)
	if sys.hexversion>0x3000000 and not'b'in m:
		m+='b'
		f=os.fdopen(fd,m)
		try:
			txt=f.read()
		finally:
			f.close()
		if encoding:
			txt=txt.decode(encoding)
		else:
			txt=txt.decode()
	else:
		f=os.fdopen(fd,m)
		try:
			txt=f.read()
		finally:
			f.close()
	return txt 

def h_file_win32(fname):
	try:
		fd=os.open(fname,os.O_BINARY|os.O_RDONLY|os.O_NOINHERIT)
	except OSError:
		raise IOError('Cannot read from %r'%fname)
	f=os.fdopen(fd,'rb')
	m=md5()
	try:
		while fname:
			fname=f.read(200000)
			m.update(fname)
	finally:
		f.close()
	return m.digest() 

def readf_win32(f,m='r',encoding='ISO8859-1'):
	flags=os.O_NOINHERIT|os.O_RDONLY
	if'b'in m:
		flags|=os.O_BINARY
	if'+'in m:
		flags|=os.O_RDWR
	try:
		fd=os.open(f,flags)
	except OSError:
		raise IOError('Cannot read from %r'%f)
	if sys.hexversion>0x3000000 and not'b'in m:
		m+='b'
		f=os.fdopen(fd,m)
		try:
			txt=f.read()
		finally:
			f.close()
		if encoding:
			txt=txt.decode(encoding)
		else:
			txt=txt.decode()
	else:
		f=os.fdopen(fd,m)
		try:
			txt=f.read()
		finally:
			f.close()
	return txt 

def h_file_win32(fname):
	try:
		fd=os.open(fname,os.O_BINARY|os.O_RDONLY|os.O_NOINHERIT)
	except OSError:
		raise IOError('Cannot read from %r'%fname)
	f=os.fdopen(fd,'rb')
	m=md5()
	try:
		while fname:
			fname=f.read(200000)
			m.update(fname)
	finally:
		f.close()
	return m.digest() 

def PutToken(self, key, value):
    """Serializes the value to the key's filename.

    To ensure that written tokens aren't leaked to a different users, we
     a) unlink an existing cache file, if any (to ensure we don't fall victim
        to symlink attacks and the like),
     b) create a new file with O_CREAT | O_EXCL (to ensure nobody is trying to
        race us)
     If either of these steps fail, we simply give up (but log a warning). Not
     caching access tokens is not catastrophic, and failure to create a file
     can happen for either of the following reasons:
      - someone is attacking us as above, in which case we want to default to
        safe operation (not write the token);
      - another legitimate process is racing us; in this case one of the two
        will win and write the access token, which is fine;
      - we don't have permission to remove the old file or write to the
        specified directory, in which case we can't recover

    Args:
      key: the hash key to store.
      value: the access_token value to serialize.
    """

    cache_file = self.CacheFileName(key)
    LOG.debug('FileSystemTokenCache.PutToken: key=%s, cache_file=%s',
              key, cache_file)
    try:
      os.unlink(cache_file)
    except:  # pylint: disable=bare-except
      # Ignore failure to unlink the file; if the file exists and can't be
      # unlinked, the subsequent open with O_CREAT | O_EXCL will fail.
      pass

    flags = os.O_RDWR | os.O_CREAT | os.O_EXCL

    # Accommodate Windows; stolen from python2.6/tempfile.py.
    if hasattr(os, 'O_NOINHERIT'):
      flags |= os.O_NOINHERIT
    if hasattr(os, 'O_BINARY'):
      flags |= os.O_BINARY

    try:
      fd = os.open(cache_file, flags, 0o600)
    except (OSError, IOError) as e:
      LOG.warning('FileSystemTokenCache.PutToken: '
                  'Failed to create cache file %s: %s', cache_file, e)
      return
    f = os.fdopen(fd, 'w+b')
    serialized = value.Serialize()
    if isinstance(serialized, six.text_type):
      serialized = serialized.encode('utf-8')
    f.write(six.ensure_binary(serialized))
    f.close()