summaryrefslogtreecommitdiffstats
path: root/Modules/_weakref.c
blob: 387b8fa9d0a6f140275eeca4714c7f6f62eeae68 (plain)
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
#include "Python.h"
#include "pycore_object.h"   // _PyObject_GET_WEAKREFS_LISTPTR


#define GET_WEAKREFS_LISTPTR(o) \
        ((PyWeakReference **) _PyObject_GET_WEAKREFS_LISTPTR(o))

/*[clinic input]
module _weakref
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=ffec73b85846596d]*/

#include "clinic/_weakref.c.h"

/*[clinic input]

_weakref.getweakrefcount -> Py_ssize_t

  object: object
  /

Return the number of weak references to 'object'.
[clinic start generated code]*/

static Py_ssize_t
_weakref_getweakrefcount_impl(PyObject *module, PyObject *object)
/*[clinic end generated code: output=301806d59558ff3e input=cedb69711b6a2507]*/
{
    PyWeakReference **list;

    if (!_PyType_SUPPORTS_WEAKREFS(Py_TYPE(object)))
        return 0;

    list = GET_WEAKREFS_LISTPTR(object);
    return _PyWeakref_GetWeakrefCount(*list);
}


static int
is_dead_weakref(PyObject *value)
{
    if (!PyWeakref_Check(value)) {
        PyErr_SetString(PyExc_TypeError, "not a weakref");
        return -1;
    }
    return PyWeakref_GET_OBJECT(value) == Py_None;
}

/*[clinic input]

_weakref._remove_dead_weakref -> object

  dct: object(subclass_of='&PyDict_Type')
  key: object
  /

Atomically remove key from dict if it points to a dead weakref.
[clinic start generated code]*/

static PyObject *
_weakref__remove_dead_weakref_impl(PyObject *module, PyObject *dct,
                                   PyObject *key)
/*[clinic end generated code: output=d9ff53061fcb875c input=19fc91f257f96a1d]*/
{
    if (_PyDict_DelItemIf(dct, key, is_dead_weakref) < 0) {
        if (PyErr_ExceptionMatches(PyExc_KeyError))
            /* This function is meant to allow safe weak-value dicts
               with GC in another thread (see issue #28427), so it's
               ok if the key doesn't exist anymore.
               */
            PyErr_Clear();
        else
            return NULL;
    }
    Py_RETURN_NONE;
}


/*[clinic input]
_weakref.getweakrefs
    object: object
    /

Return a list of all weak reference objects pointing to 'object'.
[clinic start generated code]*/

static PyObject *
_weakref_getweakrefs(PyObject *module, PyObject *object)
/*[clinic end generated code: output=25c7731d8e011824 input=00c6d0e5d3206693]*/
{
    PyObject *result = NULL;

    if (_PyType_SUPPORTS_WEAKREFS(Py_TYPE(object))) {
        PyWeakReference **list = GET_WEAKREFS_LISTPTR(object);
        Py_ssize_t count = _PyWeakref_GetWeakrefCount(*list);

        result = PyList_New(count);
        if (result != NULL) {
            PyWeakReference *current = *list;
            Py_ssize_t i;
            for (i = 0; i < count; ++i) {
                PyList_SET_ITEM(result, i, (PyObject *) current);
                Py_INCREF(current);
                current = current->wr_next;
            }
        }
    }
    else {
        result = PyList_New(0);
    }
    return result;
}


/*[clinic input]

_weakref.proxy
    object: object
    callback: object(c_default="NULL") = None
    /

Create a proxy object that weakly references 'object'.

'callback', if given, is called with a reference to the
proxy when 'object' is about to be finalized.
[clinic start generated code]*/

static PyObject *
_weakref_proxy_impl(PyObject *module, PyObject *object, PyObject *callback)
/*[clinic end generated code: output=d68fa4ad9ea40519 input=4808adf22fd137e7]*/
{
    return PyWeakref_NewProxy(object, callback);
}


static PyMethodDef
weakref_functions[] =  {
    _WEAKREF_GETWEAKREFCOUNT_METHODDEF
    _WEAKREF__REMOVE_DEAD_WEAKREF_METHODDEF
    _WEAKREF_GETWEAKREFS_METHODDEF
    _WEAKREF_PROXY_METHODDEF
    {NULL, NULL, 0, NULL}
};

static int
weakref_exec(PyObject *module)
{
    Py_INCREF(&_PyWeakref_RefType);
    if (PyModule_AddObject(module, "ref", (PyObject *) &_PyWeakref_RefType) < 0) {
        Py_DECREF(&_PyWeakref_RefType);
        return -1;
    }
    Py_INCREF(&_PyWeakref_RefType);
    if (PyModule_AddObject(module, "ReferenceType",
                           (PyObject *) &_PyWeakref_RefType) < 0) {
        Py_DECREF(&_PyWeakref_RefType);
        return -1;
    }
    Py_INCREF(&_PyWeakref_ProxyType);
    if (PyModule_AddObject(module, "ProxyType",
                           (PyObject *) &_PyWeakref_ProxyType) < 0) {
        Py_DECREF(&_PyWeakref_ProxyType);
        return -1;
    }
    Py_INCREF(&_PyWeakref_CallableProxyType);
    if (PyModule_AddObject(module, "CallableProxyType",
                           (PyObject *) &_PyWeakref_CallableProxyType) < 0) {
        Py_DECREF(&_PyWeakref_CallableProxyType);
        return -1;
    }

    return 0;
}

static struct PyModuleDef_Slot weakref_slots[] = {
    {Py_mod_exec, weakref_exec},
    {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},
    {0, NULL}
};

static struct PyModuleDef weakrefmodule = {
    PyModuleDef_HEAD_INIT,
    "_weakref",
    "Weak-reference support module.",
    0,
    weakref_functions,
    weakref_slots,
    NULL,
    NULL,
    NULL
};

PyMODINIT_FUNC
PyInit__weakref(void)
{
    return PyModuleDef_Init(&weakrefmodule);
}