Mercurial > templog
view web/atomicfile.py @ 523:21ce2b15128f
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author | Matt Johnston <matt@ucc.asn.au> |
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date | Thu, 29 Jan 2015 22:52:26 +0800 |
parents | 236e5d131b3e |
children | 87c20b8c5472 |
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import os import time import fcntl import sys class AtomicFile(object): DELAY = 0.5 def __init__(self, name): self.name = name def write(self, data, timeout = 5): try: end = time.time() + timeout with open(self.name, "r+") as f: while timeout == 0 or time.time() < end: try: fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB) except IOError: time.sleep(DELAY) continue os.ftruncate(f.fileno(), 0) f.write(data) return True except IOError, e: print>>sys.stderr, e return False def read(self, timeout = 5): try: end = time.time() + timeout with open(self.name, "r") as f: while timeout == 0 or time.time() < end: try: fcntl.lockf(f, fcntl.LOCK_SH | fcntl.LOCK_NB) except IOError: time.sleep(DELAY) continue return f.read() except IOError, e: print>>sys.stderr, e return None