#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
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 logging
import platform
logger = logging.getLogger("web2py")
os_locking = None
try:
import google.appengine
os_locking = 'gae'
except:
try:
import fcntl
os_locking = 'posix'
except:
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/')
elif os_locking != 'gae':
logger.debug('no file locking, this will cause problems')
LOCK_EX = None
LOCK_SH = None
LOCK_NB = None
[docs] def lock(file, flags):
pass
[docs]class LockedFile(object):
def __init__(self, filename, mode='rb'):
self.filename = filename
self.mode = mode
self.file = None
if 'r' in mode:
self.file = open(filename, mode)
lock(self.file, LOCK_SH)
elif 'w' in mode or 'a' in mode:
self.file = open(filename, mode.replace('w', 'a'))
lock(self.file, LOCK_EX)
if not 'a' in mode:
self.file.seek(0)
self.file.truncate()
else:
raise RuntimeError("invalid LockedFile(...,mode)")
[docs] def read(self, size=None):
return self.file.read() if size is None else self.file.read(size)
[docs] def readline(self):
return self.file.readline()
[docs] def readlines(self):
return self.file.readlines()
[docs] def write(self, data):
self.file.write(data)
self.file.flush()
[docs] def close(self):
if not self.file is None:
unlock(self.file)
self.file.close()
self.file = None
def __del__(self):
if not self.file is None:
self.close()
[docs]def read_locked(filename):
fp = LockedFile(filename, 'r')
data = fp.read()
fp.close()
return data
[docs]def write_locked(filename, data):
fp = LockedFile(filename, 'w')
data = fp.write(data)
fp.close()
if __name__ == '__main__':
import sys
f = LockedFile('test.txt', mode='wb')
f.write('test ok')
f.close()
f = LockedFile('test.txt', mode='rb')
sys.stdout.write(f.read()+'\n')
f.close()