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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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