1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
|
/*
* ====================================================================
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
* ====================================================================
*
* proxy_apr.swg: This file forms part of the core module (it is %included
* only in one place, core.i). It contains Python pool related code.
*/
#ifdef SWIGPYTHON
%nodefault apr_array_header_t;
%nodefault apr_file_t;
%nodefault apr_hash_t;
%nodefault apr_pool_t;
%opaque_proxy(apr_array_header_t);
%opaque_proxy(apr_file_t);
%opaque_proxy(apr_hash_t);
/*
* SWIG/Python Automatic Memory Management in Subversion: An Overview
* ------------------------------------------------------------------
*
* The python memory management code is designed to mark pools as invalid
* when their parent pools have been garbage collected. This is implemented
* by registering a callback with the Python garbage collector, so that when
* the object's parent pool is deleted, we can be notified. For more info on
* how these callbacks work, read the Python documentation for the
* weakref.ref() function.
*
* Each object has an _is_valid member, and stores a weakref to its parent
* pool's _is_valid, and when that weakref is broken _mark_weakpool_invalid()
* gets called in order to mark the object as invalid.
*
* You can destroy a pool in three ways:
* pool.destroy()
* pool.clear()
* pool.__del__()
*
* Each of the above functions destroys the pool's _is_valid member, setting
* off a cascade of callback functions that set all the child objects that were
* created in the pool to invalid.
*
* If a SWIG object is created from a memory pool, the Python wrapper should
* store a full reference to the memory pool and a weakreference to _is_valid.
* When you try to access the SWIG object, the Python wrapper will check the
* _is_valid weakref to ensure that the pool has not been destroyed (see
* proxy.swg to read the implementation details).
*
* This lets us gracefully throw an exception if you try to use an object
* that was allocated out of a pool that was cleared, rather than crashing
* like we used to do.
*
*/
%pythoncode %{
import threading
application_pool = None
application_pool_lock = threading.Lock()
class GenericSWIGWrapper:
def __init__(self, this, pool):
"""Create new Generic SWIG wrapper object"""
import weakref
self.this = this
self._parent_pool = pool
self._is_valid = weakref.ref(pool._is_valid)
def set_parent_pool(self, pool):
"""Set the parent pool of this object"""
self._parent_pool = pool
def valid(self):
"""Is this object valid?"""
return self._is_valid()
def assert_valid(self):
"""Assert that this object is still valid"""
assert self.valid(), "This object has already been destroyed"
def _unwrap(self):
"""Return underlying SWIG object"""
self.assert_valid()
return self.this
def _mark_weakpool_invalid(weakpool):
if weakpool and weakpool() and hasattr(weakpool(), "_is_valid"):
del weakpool()._is_valid
%}
struct apr_pool_t {
%extend {
%pythoncode %{
def set_parent_pool(self, parent_pool=None):
"""Create a new memory pool"""
global application_pool
try:
application_pool_lock.acquire()
self._parent_pool = parent_pool or application_pool
self._mark_valid()
# Protect important functions from GC
self._apr_pool_destroy = _core.apr_pool_destroy
self._svn_swig_py_clear_application_pool = \
_core.svn_swig_py_clear_application_pool
# If we are an application-level pool,
# then set this pool to be the application-level pool
if not self._parent_pool:
svn_swig_py_set_application_pool(self, self)
application_pool = self
finally:
application_pool_lock.release()
def valid(self):
"""Check whether this memory pool and its parents
are still valid"""
return hasattr(self,"_is_valid")
def assert_valid(self):
"""Assert that this memory_pool is still valid."""
assert self.valid(), "This pool has already been destroyed"
def clear(self):
"""Clear embedded memory pool. Invalidate all subpools."""
pool = self._parent_pool
apr_pool_clear(self)
self.set_parent_pool(pool)
def destroy(self):
"""Destroy embedded memory pool. If you do not destroy
the memory pool manually, Python will destroy it
automatically."""
global application_pool
self.assert_valid()
is_application_pool = not self._parent_pool
# Destroy pool
self._apr_pool_destroy(self)
# Clear application pool if necessary
if is_application_pool:
application_pool = None
self._svn_swig_py_clear_application_pool()
# Mark self as invalid
if hasattr(self, "_parent_pool"):
del self._parent_pool
if hasattr(self, "_is_valid"):
del self._is_valid
def __del__(self):
"""Automatically destroy memory pools, if necessary"""
if self.valid():
self.destroy()
def _mark_valid(self):
"""Mark pool as valid"""
self._weakparent = None
if self._parent_pool:
import weakref
# Make sure that the parent object is valid
self._parent_pool.assert_valid()
# Refer to self using a weakrefrence so that we don't
# create a reference cycle
weakself = weakref.ref(self)
# Set up callbacks to mark pool as invalid when parents
# are destroyed
self._weakparent = weakref.ref(self._parent_pool._is_valid,
lambda x: _mark_weakpool_invalid(weakself))
# Mark pool as valid
self._is_valid = lambda: 1
def _wrap(self, obj):
"""Mark a SWIG object as owned by this pool"""
self.assert_valid()
if hasattr(obj, "set_parent_pool"):
obj.set_parent_pool(self)
return obj
elif obj is None:
return None
else:
return GenericSWIGWrapper(obj, self)
%}
}
};
%pythoncode %{
# Initialize a global pool
svn_pool_create()
%}
#endif
|
