#!/usr/bin/env python
# -*- coding: utf-8 -*-
# portalocker.py - Cross-platform (posix/nt) API for flock-style file locking.
# Requires python 1.5.2 or better.
"""
Cross-platform (posix/nt) API for flock-style file locking.
Synopsis:
import portalocker
file = open(\"somefile\", \"r+\")
portalocker.lock(file, portalocker.LOCK_EX)
file.seek(12)
file.write(\"foo\")
file.close()
If you know what you're doing, you may choose to
portalocker.unlock(file)
before closing the file, but why?
Methods:
lock( file, flags )
unlock( file )
Constants:
LOCK_EX
LOCK_SH
LOCK_NB
I learned the win32 technique for locking files from sample code
provided by John Nielsen <nielsenjf@my-deja.com> in the documentation
that accompanies the win32 modules.
Author: Jonathan Feinberg <jdf@pobox.com>
Version: $Id: portalocker.py,v 1.3 2001/05/29 18:47:55 Administrator Exp $
"""
import os
import logging
import platform
logger = logging.getLogger("web2py")
os_locking = None
try:
import fcntl
os_locking = 'posix'
except:
pass
try:
import win32con
import win32file
import pywintypes
os_locking = 'windows'
except:
pass
if os_locking == 'windows':
LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
LOCK_SH = 0 # the default
LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
# is there any reason not to reuse the following structure?
__overlapped = pywintypes.OVERLAPPED()
def lock(file, flags):
hfile = win32file._get_osfhandle(file.fileno())
win32file.LockFileEx(hfile, flags, 0, 0x7fff0000, __overlapped)
def unlock(file):
hfile = win32file._get_osfhandle(file.fileno())
win32file.UnlockFileEx(hfile, 0, 0x7fff0000, __overlapped)
elif os_locking == 'posix':
LOCK_EX = fcntl.LOCK_EX
LOCK_SH = fcntl.LOCK_SH
LOCK_NB = fcntl.LOCK_NB
def lock(file, flags):
fcntl.flock(file.fileno(), flags)
def unlock(file):
fcntl.flock(file.fileno(), fcntl.LOCK_UN)
else:
if platform.system() == 'Windows':
logger.error('no file locking, you must install the win32 extensions from: http://sourceforge.net/projects/pywin32/files/')
else:
logger.debug('no file locking, this will cause problems')
LOCK_EX = None
LOCK_SH = None
LOCK_NB = None
def lock(file, flags):
pass
def unlock(file):
pass
if __name__ == '__main__':
from time import time, strftime, localtime
import sys
log = open('log.txt', 'a+')
lock(log, LOCK_EX)
timestamp = strftime('%m/%d/%Y %H:%M:%S\n', localtime(time()))
log.write(timestamp)
print 'Wrote lines. Hit enter to release lock.'
dummy = sys.stdin.readline()
log.close()