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import os
import fcntl
try:
# py 3
from urllib import parse as urllib
except ImportError:
import urllib
def escape(s):
return urllib.quote_plus(s)
def unescape(s):
return urllib.unquote_plus(s)
def update_file(path, updater, merger = lambda f: True):
"""update a file in a transaction-like manner"""
fr = fw = None
try:
fd = os.open(path, os.O_CREAT|os.O_RDWR)
try:
fr = os.fdopen(fd, 'r+b')
except:
os.close(fd)
raise
fcntl.lockf(fr, fcntl.LOCK_EX)
merger(fr)
tmpp = path + '.tmp.' + str(os.getpid())
fd = os.open(tmpp, os.O_CREAT|os.O_EXCL|os.O_WRONLY)
try:
fw = os.fdopen(fd, 'wb', 0)
except:
os.close(fd)
raise
updater(fw)
os.fsync(fd)
os.rename(tmpp, path)
finally:
for fx in (fr, fw):
if fx:
fx.close()
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