cpython/Modules/_weakref.c

#include "Python.h"


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


static char weakref_getweakrefcount__doc__[] =
"getweakrefcount(object) -- return the number of weak references\n"
"to 'object'.";

static PyObject *
weakref_getweakrefcount(PyObject *self, PyObject *object)
{
    PyObject *result = NULL;

    if (PyType_SUPPORTS_WEAKREFS(object->ob_type)) {
        PyWeakReference **list = GET_WEAKREFS_LISTPTR(object);

        result = PyInt_FromLong(_PyWeakref_GetWeakrefCount(*list));
    }
    else
        result = PyInt_FromLong(0);

    return result;
}


static char weakref_getweakrefs__doc__[] =
"getweakrefs(object) -- return a list of all weak reference objects\n"
"that point to 'object'.";

static PyObject *
weakref_getweakrefs(PyObject *self, PyObject *object)
{
    PyObject *result = NULL;

    if (PyType_SUPPORTS_WEAKREFS(object->ob_type)) {
        PyWeakReference **list = GET_WEAKREFS_LISTPTR(object);
        long count = _PyWeakref_GetWeakrefCount(*list);

        result = PyList_New(count);
        if (result != NULL) {
            PyWeakReference *current = *list;
            long 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;
}


static char weakref_ref__doc__[] =
"new(object[, callback]) -- create a weak reference to 'object';\n"
"when 'object' is finalized, 'callback' will be called and passed\n"
"a reference to 'object'.";

static PyObject *
weakref_ref(PyObject *self, PyObject *args)
{
    PyObject *object;
    PyObject *callback = NULL;
    PyObject *result = NULL;

    if (PyArg_UnpackTuple(args, "ref", 1, 2, &object, &callback)) {
        result = PyWeakref_NewRef(object, callback);
    }
    return result;
}


static char weakref_proxy__doc__[] =
"proxy(object[, callback]) -- create a proxy object that weakly\n"
"references 'object'.  'callback', if given, is called with a\n"
"reference to the proxy when it is about to be finalized.";

static PyObject *
weakref_proxy(PyObject *self, PyObject *args)
{
    PyObject *object;
    PyObject *callback = NULL;
    PyObject *result = NULL;

    if (PyArg_UnpackTuple(args, "proxy", 1, 2, &object, &callback)) {
        result = PyWeakref_NewProxy(object, callback);
    }
    return result;
}


static PyMethodDef
weakref_functions[] =  {
    {"getweakrefcount", weakref_getweakrefcount,        METH_O,
     weakref_getweakrefcount__doc__},
    {"getweakrefs",     weakref_getweakrefs,            METH_O,
     weakref_getweakrefs__doc__},
    {"proxy",           weakref_proxy,                  METH_VARARGS,
     weakref_proxy__doc__},
    {"ref",             weakref_ref,                    METH_VARARGS,
     weakref_ref__doc__},
    {NULL, NULL, 0, NULL}
};


DL_EXPORT(void)
init_weakref(void)
{
    PyObject *m;

    m = Py_InitModule3("_weakref", weakref_functions,
                       "Weak-reference support module.");
    if (m != NULL) {
        Py_INCREF(&_PyWeakref_RefType);
        PyModule_AddObject(m, "ReferenceType",
                           (PyObject *) &_PyWeakref_RefType);
        Py_INCREF(&_PyWeakref_ProxyType);
        PyModule_AddObject(m, "ProxyType",
                           (PyObject *) &_PyWeakref_ProxyType);
        Py_INCREF(&_PyWeakref_CallableProxyType);
        PyModule_AddObject(m, "CallableProxyType",
                           (PyObject *) &_PyWeakref_CallableProxyType);
    }
}