|
3474.1.2
by Martin Pool
CountedLock.unlock should raise LockNotHeld if appropriate |
1 |
# Copyright (C) 2007, 2008 Canonical Ltd
|
|
2475.4.1
by Martin Pool
Start adding CountedLock class to partially replace LockableFiles |
2 |
#
|
3 |
# This program is free software; you can redistribute it and/or modify
|
|
4 |
# it under the terms of the GNU General Public License as published by
|
|
5 |
# the Free Software Foundation; either version 2 of the License, or
|
|
6 |
# (at your option) any later version.
|
|
7 |
#
|
|
8 |
# This program is distributed in the hope that it will be useful,
|
|
9 |
# but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
10 |
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
11 |
# GNU General Public License for more details.
|
|
12 |
#
|
|
13 |
# You should have received a copy of the GNU General Public License
|
|
14 |
# along with this program; if not, write to the Free Software
|
|
15 |
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
|
|
16 |
||
17 |
"""Counted lock class"""
|
|
18 |
||
19 |
||
|
3474.1.2
by Martin Pool
CountedLock.unlock should raise LockNotHeld if appropriate |
20 |
from bzrlib import ( |
21 |
errors, |
|
|
2475.4.1
by Martin Pool
Start adding CountedLock class to partially replace LockableFiles |
22 |
)
|
23 |
||
24 |
||
25 |
class CountedLock(object): |
|
26 |
"""Decorator around a lock that makes it reentrant.
|
|
27 |
||
28 |
This can be used with any object that provides a basic Lock interface,
|
|
29 |
including LockDirs and OS file locks.
|
|
30 |
"""
|
|
31 |
||
32 |
def __init__(self, real_lock): |
|
33 |
self._real_lock = real_lock |
|
34 |
self._lock_mode = None |
|
35 |
self._lock_count = 0 |
|
36 |
||
|
3474.1.2
by Martin Pool
CountedLock.unlock should raise LockNotHeld if appropriate |
37 |
def __repr__(self): |
38 |
return "%s(%r)" % (self.__class__.__name__, |
|
39 |
self._real_lock) |
|
40 |
||
|
2475.4.1
by Martin Pool
Start adding CountedLock class to partially replace LockableFiles |
41 |
def break_lock(self): |
42 |
self._real_lock.break_lock() |
|
43 |
self._lock_mode = None |
|
44 |
self._lock_count = 0 |
|
45 |
||
46 |
def is_locked(self): |
|
47 |
return self._lock_mode is not None |
|
48 |
||
49 |
def lock_read(self): |
|
50 |
"""Acquire the lock in read mode.
|
|
51 |
||
52 |
If the lock is already held in either read or write mode this
|
|
53 |
increments the count and succeeds. If the lock is not already held,
|
|
54 |
it is taken in read mode.
|
|
55 |
"""
|
|
56 |
if self._lock_mode: |
|
57 |
self._lock_count += 1 |
|
58 |
else: |
|
59 |
self._real_lock.lock_read() |
|
60 |
self._lock_count = 1 |
|
61 |
self._lock_mode = 'r' |
|
62 |
||
|
3474.1.3
by Martin Pool
CountedLock now handles and tests lock tokens |
63 |
def lock_write(self, token=None): |
|
2475.4.1
by Martin Pool
Start adding CountedLock class to partially replace LockableFiles |
64 |
"""Acquire the lock in write mode.
|
65 |
||
66 |
If the lock was originally acquired in read mode this will fail.
|
|
|
3474.1.3
by Martin Pool
CountedLock now handles and tests lock tokens |
67 |
|
68 |
:param token: If non-None, reacquire the lock using this token.
|
|
|
2475.4.1
by Martin Pool
Start adding CountedLock class to partially replace LockableFiles |
69 |
"""
|
70 |
if self._lock_count == 0: |
|
|
3474.1.3
by Martin Pool
CountedLock now handles and tests lock tokens |
71 |
return_token = self._real_lock.lock_write(token) |
|
2475.4.1
by Martin Pool
Start adding CountedLock class to partially replace LockableFiles |
72 |
self._lock_mode = 'w' |
|
3474.1.3
by Martin Pool
CountedLock now handles and tests lock tokens |
73 |
self._lock_count += 1 |
74 |
return return_token |
|
|
2475.4.1
by Martin Pool
Start adding CountedLock class to partially replace LockableFiles |
75 |
elif self._lock_mode != 'w': |
|
3474.1.2
by Martin Pool
CountedLock.unlock should raise LockNotHeld if appropriate |
76 |
raise errors.ReadOnlyError(self) |
|
3474.1.3
by Martin Pool
CountedLock now handles and tests lock tokens |
77 |
else: |
78 |
self._real_lock.validate_token(token) |
|
79 |
self._lock_count += 1 |
|
80 |
return token |
|
|
2475.4.1
by Martin Pool
Start adding CountedLock class to partially replace LockableFiles |
81 |
|
82 |
def unlock(self): |
|
83 |
if self._lock_count == 0: |
|
|
3474.1.3
by Martin Pool
CountedLock now handles and tests lock tokens |
84 |
raise errors.LockNotHeld(self) |
|
2475.4.1
by Martin Pool
Start adding CountedLock class to partially replace LockableFiles |
85 |
elif self._lock_count == 1: |
|
3474.1.3
by Martin Pool
CountedLock now handles and tests lock tokens |
86 |
# these are decremented first; if we fail to unlock the most
|
87 |
# reasonable assumption is that we still don't have the lock
|
|
88 |
# anymore
|
|
89 |
self._lock_mode = None |
|
90 |
self._lock_count -= 1 |
|
|
2475.4.1
by Martin Pool
Start adding CountedLock class to partially replace LockableFiles |
91 |
self._real_lock.unlock() |
|
3474.1.3
by Martin Pool
CountedLock now handles and tests lock tokens |
92 |
else: |
93 |
self._lock_count -= 1 |