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comparison web/atomicfile.py @ 501:236e5d131b3e

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Add url link, improve atomicfile
author Matt Johnston <matt@ucc.asn.au>
date Sun, 30 Mar 2014 20:20:30 +0800
parents 46e327c00246
children 87c20b8c5472
comparison
equal deleted inserted replaced
500:136b1343e640 501:236e5d131b3e
2 import time 2 import time
3 import fcntl 3 import fcntl
4 import sys 4 import sys
5 5
6 class AtomicFile(object): 6 class AtomicFile(object):
7 DELAY = 0.5 7 DELAY = 0.5
8 def __init__(self, name): 8 def __init__(self, name):
9 self.name = name 9 self.name = name
10 10
11 def write(self, data, timeout = 5): 11 def write(self, data, timeout = 5):
12 try: 12 try:
13 end = time.time() + timeout 13 end = time.time() + timeout
14 with open(self.name, "r+") as f: 14 with open(self.name, "r+") as f:
15 while timeout == 0 or time.time() < end: 15 while timeout == 0 or time.time() < end:
16 try: 16 try:
17 fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB) 17 fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
18 except IOError: 18 except IOError:
19 time.sleep(DELAY) 19 time.sleep(DELAY)
20 continue 20 continue
21 21
22 f.write(data) 22 os.ftruncate(f.fileno(), 0)
23 return True 23 f.write(data)
24 return True
24 25
25 except IOError, e: 26 except IOError, e:
26 print>>sys.stderr, e 27 print>>sys.stderr, e
27 28
28 return False 29 return False
29 30
30 def read(self, timeout = 5): 31 def read(self, timeout = 5):
31 try: 32 try:
32 end = time.time() + timeout 33 end = time.time() + timeout
33 with open(self.name, "r") as f: 34 with open(self.name, "r") as f:
34 while timeout == 0 or time.time() < end: 35 while timeout == 0 or time.time() < end:
35 try: 36 try:
36 fcntl.lockf(f, fcntl.LOCK_SH | fcntl.LOCK_NB) 37 fcntl.lockf(f, fcntl.LOCK_SH | fcntl.LOCK_NB)
37 except IOError: 38 except IOError:
38 time.sleep(DELAY) 39 time.sleep(DELAY)
39 continue 40 continue
40 41
41 return f.read() 42 return f.read()
42 43
43 except IOError, e: 44 except IOError, e:
44 print>>sys.stderr, e 45 print>>sys.stderr, e
45 46
46 return None 47 return None