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# Copyright (C) 2005, 2006 Canonical Ltd
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# Copyright (C) 2005 Canonical Ltd
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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"""Locking using OS file locks or file existence.
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Note: This method of locking is generally deprecated in favour of LockDir, but
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is used to lock local WorkingTrees, and by some old formats. It's accessed
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through Transport.lock_read(), etc.
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This only does local locking using OS locks for now.
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This module causes two methods, lock() and unlock() to be defined in
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any way that works on the current platform.
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It is not specified whether these locks are reentrant (i.e. can be
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taken repeatedly by a single process) or whether they exclude
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different threads in a single process. That reentrancy is provided by
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different threads in a single process.
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Eventually we may need to use some kind of lock representation that
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will work on a dumb filesystem without actual locking primitives.
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This defines two classes: ReadLock and WriteLock, which can be
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implemented in different ways on different platforms. Both have an
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from bzrlib.trace import mutter, note, warning
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from bzrlib.errors import LockError
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from bzrlib.osutils import realpath
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from bzrlib.trace import mutter
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class _base_Lock(object):
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def _open(self, filename, filemode):
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self.f = open(filename, filemode)
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class _fcntl_FileLock(_base_Lock):
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fcntl.lockf(self.f, fcntl.LOCK_UN)
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"""Clear the self.f attribute cleanly."""
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class _fcntl_WriteLock(_fcntl_FileLock):
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def __init__(self, filename):
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# standard IO errors get exposed directly.
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self._open(filename, 'wb')
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self.filename = realpath(filename)
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if self.filename in self.open_locks:
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raise LockError("Lock already held.")
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# reserve a slot for this lock - even if the lockf call fails,
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# at thisi point unlock() will be called, because self.f is set.
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# TODO: make this fully threadsafe, if we decide we care.
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self.open_locks[self.filename] = self.filename
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fcntl.lockf(self.f, fcntl.LOCK_EX)
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except IOError, e:
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# we should be more precise about whats a locking
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# error and whats a random-other error
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raise LockError(e)
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del self.open_locks[self.filename]
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class _fcntl_ReadLock(_fcntl_FileLock):
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def __init__(self, filename):
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raise LockError(e)
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class _w32c_ReadLock(_w32c_FileLock):
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def __init__(self, filename):
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_w32c_FileLock._lock(self, filename, 'rb',
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_msvc_lock(self._open(filename, 'wb'), self.LOCK_EX)
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def _msvc_lock(f, flags):
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# Unfortunately, msvcrt.LK_RLCK is equivalent to msvcrt.LK_LOCK
added
removed
bzrlib/lock.py
