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comparison web/atomicfile.py @ 489:46e327c00246

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gets current params
author Matt Johnston <matt@ucc.asn.au>
date Tue, 11 Feb 2014 22:10:32 +0800
parents
children 6dd157a12035
comparison
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488:4792e9910cde 489:46e327c00246
1 import os
2 import time
3 import fcntl
4 import sys
5
6 class AtomicFile(object):
7 DELAY = 0.5
8 def __init__(self, name):
9 self.name = name
10
11 def write(self, data, timeout = 5):
12 try:
13 end = time.time() + timeout
14 with open(self.name, "r+") as f:
15 while timeout == 0 or time.time() < end:
16 try:
17 fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
18 except IOError:
19 time.sleep(DELAY)
20 continue
21
22 f.write(data)
23 return True
24
25 except IOError, e:
26 print>>sys.stderr, e
27
28 return False
29
30 def read(self, timeout = 5):
31 try:
32 end = time.time() + timeout
33 with open(self.name, "r") as f:
34 while timeout == 0 or time.time() < end:
35 try:
36 fcntl.lockf(f, fcntl.LOCK_SH | fcntl.LOCK_NB)
37 except IOError:
38 time.sleep(DELAY)
39 continue
40
41 return f.read()
42
43 except IOError, e:
44 print>>sys.stderr, e
45
46 return None