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bzrlib/lock.py
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import os
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import sys
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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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from bzrlib.errors import LockError
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class _base_Lock(object):
 
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    def _open(self, filename, filemode):
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        try:
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            self.f = open(filename, filemode)
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    import fcntl
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    class _fcntl_FileLock(_base_Lock):
 
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        f = None
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        def unlock(self):
 
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        def _unlock(self):
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            fcntl.lockf(self.f, fcntl.LOCK_UN)
 
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            self._clear_f()
 
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        def _clear_f(self):
 
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            """Clear the self.f attribute cleanly."""
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            self.f.close()
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            del self.f 
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    class _fcntl_WriteLock(_fcntl_FileLock):
 
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        open_locks = {}
 
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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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            try:
 
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                self.filename = realpath(filename)
 
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                if self.filename in self.open_locks:
 
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                    self._clear_f() 
 
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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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        def unlock(self):
 
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            del self.open_locks[self.filename]
 
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            self._unlock()
 
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    class _fcntl_ReadLock(_fcntl_FileLock):
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        def __init__(self, filename):
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                # error and whats a random-other error
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                raise LockError(e)
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        def unlock(self):
 
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            self._unlock()
 
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    WriteLock = _fcntl_WriteLock
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    ReadLock = _fcntl_ReadLock
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