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# lock.py - simple locking scheme for mercurial
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#
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# Copyright 2005 Matt Mackall <mpm@selenic.com>
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#
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# This software may be used and distributed according to the terms
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# of the GNU General Public License, incorporated herein by reference.
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import os, time
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class LockHeld(Exception):
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pass
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class lock:
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def __init__(self, file, wait = 1):
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self.f = file
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self.held = 0
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self.wait = wait
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self.lock()
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def __del__(self):
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self.release()
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def lock(self):
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while 1:
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try:
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self.trylock()
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return 1
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except LockHeld, inst:
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if self.wait:
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time.sleep(1)
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continue
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raise inst
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def trylock(self):
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pid = os.getpid()
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try:
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os.symlink(str(pid), self.f)
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self.held = 1
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except:
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raise LockHeld(os.readlink(self.f))
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def release(self):
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if self.held:
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self.held = 0
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os.unlink(self.f)
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