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cpython/Modules/_weakref.c

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#include "Python.h"
#include "structmember.h"
typedef struct _PyWeakReference PyWeakReference;
struct _PyWeakReference {
PyObject_HEAD
PyObject *wr_object;
PyObject *wr_callback;
PyWeakReference *wr_prev;
PyWeakReference *wr_next;
};
#define GET_WEAKREFS_LISTPTR(o) \
((PyWeakReference **) PyObject_GET_WEAKREFS_LISTPTR(o))
static PyObject *
ReferenceError;
static PyWeakReference *
free_list = NULL;
staticforward PyTypeObject
PyWeakReference_Type;
static PyWeakReference *
new_weakref(void)
{
PyWeakReference *result;
if (free_list != NULL) {
result = free_list;
free_list = result->wr_next;
result->ob_type = &PyWeakReference_Type;
_Py_NewReference((PyObject *)result);
}
else {
result = PyObject_NEW(PyWeakReference, &PyWeakReference_Type);
}
return result;
}
/* This function clears the passed-in reference and removes it from the
* list of weak references for the referent. This is the only code that
* removes an item from the doubly-linked list of weak references for an
* object; it is also responsible for clearing the callback slot.
*/
static void
clear_weakref(PyWeakReference *self)
{
PyObject *callback = self->wr_callback;
if (self->wr_object != Py_None) {
PyWeakReference **list = GET_WEAKREFS_LISTPTR(self->wr_object);
if (*list == self)
*list = self->wr_next;
self->wr_object = Py_None;
self->wr_callback = NULL;
if (self->wr_prev != NULL)
self->wr_prev->wr_next = self->wr_next;
if (self->wr_next != NULL)
self->wr_next->wr_prev = self->wr_prev;
self->wr_prev = NULL;
self->wr_next = NULL;
Py_XDECREF(callback);
}
}
static void
weakref_dealloc(PyWeakReference *self)
{
clear_weakref(self);
PyObject_GC_Fini((PyObject *)self);
self->wr_next = free_list;
free_list = self;
}
static int
gc_traverse(PyWeakReference *self, visitproc visit, void *arg)
{
if (self->wr_callback != NULL)
return visit(self->wr_callback, arg);
return 0;
}
static int
gc_clear(PyWeakReference *self)
{
clear_weakref(self);
return 0;
}
static PyObject *
weakref_call(PyWeakReference *self, PyObject *args, PyObject *kw)
{
static char *argnames[] = {NULL};
if (PyArg_ParseTupleAndKeywords(args, kw, ":__call__", argnames)) {
PyObject *object = self->wr_object;
Py_INCREF(object);
return (object);
}
return NULL;
}
static PyObject *
weakref_repr(PyWeakReference *self)
{
char buffer[256];
if (self->wr_object == Py_None) {
sprintf(buffer, "<weakref at %lx; dead>",
(long)(self));
}
else {
sprintf(buffer, "<weakref at %#lx; to '%s' at %#lx>",
(long)(self), self->wr_object->ob_type->tp_name,
(long)(self->wr_object));
}
return PyString_FromString(buffer);
}
statichere PyTypeObject
PyWeakReference_Type = {
PyObject_HEAD_INIT(NULL)
0,
"weakref",
sizeof(PyWeakReference) + PyGC_HEAD_SIZE,
0,
(destructor)weakref_dealloc,/*tp_dealloc*/
0, /*tp_print*/
0, /*tp_getattr*/
0, /*tp_setattr*/
0, /*tp_compare*/
(reprfunc)weakref_repr, /*tp_repr*/
0, /*tp_as_number*/
0, /*tp_as_sequence*/
0, /*tp_as_mapping*/
0, /*tp_hash*/
(ternaryfunc)weakref_call, /*tp_call*/
0, /*tp_str*/
0, /*tp_getattro*/
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_GC,
0, /*tp_doc*/
(traverseproc)gc_traverse, /*tp_traverse*/
(inquiry)gc_clear, /*tp_clear*/
};
static int
proxy_checkref(PyWeakReference *proxy)
{
if (proxy->wr_object == Py_None) {
PyErr_SetString(ReferenceError,
"weakly-referenced object no longer exists");
return 0;
}
return 1;
}
#define WRAP_UNARY(method, generic) \
static PyObject * \
method(PyWeakReference *proxy) { \
if (!proxy_checkref(proxy)) { \
return NULL; \
} \
return generic(proxy->wr_object); \
}
#define WRAP_BINARY(method, generic) \
static PyObject * \
method(PyWeakReference *proxy, PyObject *v) { \
if (!proxy_checkref(proxy)) { \
return NULL; \
} \
return generic(proxy->wr_object, v); \
}
#define WRAP_TERNARY(method, generic) \
static PyObject * \
method(PyWeakReference *proxy, PyObject *v, PyObject *w) { \
if (!proxy_checkref(proxy)) { \
return NULL; \
} \
return generic(proxy->wr_object, v, w); \
}
/* direct slots */
WRAP_BINARY(proxy_getattr, PyObject_GetAttr)
WRAP_UNARY(proxy_str, PyObject_Str)
WRAP_TERNARY(proxy_call, PyEval_CallObjectWithKeywords)
static int
proxy_print(PyWeakReference *proxy, FILE *fp, int flags)
{
if (!proxy_checkref(proxy))
return -1;
return PyObject_Print(proxy->wr_object, fp, flags);
}
static PyObject *
proxy_repr(PyWeakReference *proxy)
{
char buf[160];
sprintf(buf, "<weakref at %p to %.100s at %p>", proxy,
proxy->wr_object->ob_type->tp_name, proxy->wr_object);
return PyString_FromString(buf);
}
static int
proxy_setattr(PyWeakReference *proxy, PyObject *name, PyObject *value)
{
if (!proxy_checkref(proxy))
return -1;
return PyObject_SetAttr(proxy->wr_object, name, value);
}
static int
proxy_compare(PyWeakReference *proxy, PyObject *v)
{
if (!proxy_checkref(proxy))
return -1;
return PyObject_Compare(proxy->wr_object, v);
}
/* number slots */
WRAP_BINARY(proxy_add, PyNumber_Add)
WRAP_BINARY(proxy_sub, PyNumber_Subtract)
WRAP_BINARY(proxy_mul, PyNumber_Multiply)
WRAP_BINARY(proxy_div, PyNumber_Divide)
WRAP_BINARY(proxy_mod, PyNumber_Remainder)
WRAP_BINARY(proxy_divmod, PyNumber_Divmod)
WRAP_TERNARY(proxy_pow, PyNumber_Power)
WRAP_UNARY(proxy_neg, PyNumber_Negative)
WRAP_UNARY(proxy_pos, PyNumber_Positive)
WRAP_UNARY(proxy_abs, PyNumber_Absolute)
WRAP_UNARY(proxy_invert, PyNumber_Invert)
WRAP_BINARY(proxy_lshift, PyNumber_Lshift)
WRAP_BINARY(proxy_rshift, PyNumber_Rshift)
WRAP_BINARY(proxy_and, PyNumber_And)
WRAP_BINARY(proxy_xor, PyNumber_Xor)
WRAP_BINARY(proxy_or, PyNumber_Or)
WRAP_UNARY(proxy_int, PyNumber_Int)
WRAP_UNARY(proxy_long, PyNumber_Long)
WRAP_UNARY(proxy_float, PyNumber_Float)
WRAP_BINARY(proxy_iadd, PyNumber_InPlaceAdd)
WRAP_BINARY(proxy_isub, PyNumber_InPlaceSubtract)
WRAP_BINARY(proxy_imul, PyNumber_InPlaceMultiply)
WRAP_BINARY(proxy_idiv, PyNumber_InPlaceDivide)
WRAP_BINARY(proxy_imod, PyNumber_InPlaceRemainder)
WRAP_TERNARY(proxy_ipow, PyNumber_InPlacePower)
WRAP_BINARY(proxy_ilshift, PyNumber_InPlaceLshift)
WRAP_BINARY(proxy_irshift, PyNumber_InPlaceRshift)
WRAP_BINARY(proxy_iand, PyNumber_InPlaceAnd)
WRAP_BINARY(proxy_ixor, PyNumber_InPlaceXor)
WRAP_BINARY(proxy_ior, PyNumber_InPlaceOr)
static int
proxy_nonzero(PyWeakReference *proxy)
{
PyObject *o = proxy->wr_object;
if (!proxy_checkref(proxy))
return 1;
if (o->ob_type->tp_as_number &&
o->ob_type->tp_as_number->nb_nonzero)
return (*o->ob_type->tp_as_number->nb_nonzero)(o);
else
return 1;
}
/* sequence slots */
static PyObject *
proxy_slice(PyWeakReference *proxy, int i, int j)
{
if (!proxy_checkref(proxy))
return NULL;
return PySequence_GetSlice(proxy->wr_object, i, j);
}
static int
proxy_ass_slice(PyWeakReference *proxy, int i, int j, PyObject *value)
{
if (!proxy_checkref(proxy))
return -1;
return PySequence_SetSlice(proxy->wr_object, i, j, value);
}
static int
proxy_contains(PyWeakReference *proxy, PyObject *value)
{
if (!proxy_checkref(proxy))
return -1;
return PySequence_Contains(proxy->wr_object, value);
}
/* mapping slots */
static int
proxy_length(PyWeakReference *proxy)
{
if (!proxy_checkref(proxy))
return -1;
return PyObject_Length(proxy->wr_object);
}
WRAP_BINARY(proxy_getitem, PyObject_GetItem)
static int
proxy_setitem(PyWeakReference *proxy, PyObject *key, PyObject *value)
{
if (!proxy_checkref(proxy))
return -1;
return PyObject_SetItem(proxy->wr_object, key, value);
}
static PyNumberMethods proxy_as_number = {
(binaryfunc)proxy_add, /*nb_add*/
(binaryfunc)proxy_sub, /*nb_subtract*/
(binaryfunc)proxy_mul, /*nb_multiply*/
(binaryfunc)proxy_div, /*nb_divide*/
(binaryfunc)proxy_mod, /*nb_remainder*/
(binaryfunc)proxy_divmod, /*nb_divmod*/
(ternaryfunc)proxy_pow, /*nb_power*/
(unaryfunc)proxy_neg, /*nb_negative*/
(unaryfunc)proxy_pos, /*nb_positive*/
(unaryfunc)proxy_abs, /*nb_absolute*/
(inquiry)proxy_nonzero, /*nb_nonzero*/
(unaryfunc)proxy_invert, /*nb_invert*/
(binaryfunc)proxy_lshift, /*nb_lshift*/
(binaryfunc)proxy_rshift, /*nb_rshift*/
(binaryfunc)proxy_and, /*nb_and*/
(binaryfunc)proxy_xor, /*nb_xor*/
(binaryfunc)proxy_or, /*nb_or*/
(coercion)0, /*nb_coerce*/
(unaryfunc)proxy_int, /*nb_int*/
(unaryfunc)proxy_long, /*nb_long*/
(unaryfunc)proxy_float, /*nb_float*/
(unaryfunc)0, /*nb_oct*/
(unaryfunc)0, /*nb_hex*/
(binaryfunc)proxy_iadd, /*nb_inplace_add*/
(binaryfunc)proxy_isub, /*nb_inplace_subtract*/
(binaryfunc)proxy_imul, /*nb_inplace_multiply*/
(binaryfunc)proxy_idiv, /*nb_inplace_divide*/
(binaryfunc)proxy_imod, /*nb_inplace_remainder*/
(ternaryfunc)proxy_ipow, /*nb_inplace_power*/
(binaryfunc)proxy_ilshift, /*nb_inplace_lshift*/
(binaryfunc)proxy_irshift, /*nb_inplace_rshift*/
(binaryfunc)proxy_iand, /*nb_inplace_and*/
(binaryfunc)proxy_ixor, /*nb_inplace_xor*/
(binaryfunc)proxy_ior, /*nb_inplace_or*/
};
static PySequenceMethods proxy_as_sequence = {
(inquiry)proxy_length, /*sq_length*/
0, /*sq_concat*/
0, /*sq_repeat*/
0, /*sq_item*/
(intintargfunc)proxy_slice, /*sq_slice*/
0, /*sq_ass_item*/
(intintobjargproc)proxy_ass_slice, /*sq_ass_slice*/
(objobjproc)proxy_contains, /* sq_contains */
};
static PyMappingMethods proxy_as_mapping = {
(inquiry)proxy_length, /*mp_length*/
(binaryfunc)proxy_getitem, /*mp_subscript*/
(objobjargproc)proxy_setitem, /*mp_ass_subscript*/
};
static PyTypeObject
PyWeakProxy_Type = {
PyObject_HEAD_INIT(NULL)
0,
"weakproxy",
sizeof(PyWeakReference) + PyGC_HEAD_SIZE,
0,
/* methods */
(destructor)weakref_dealloc,/*tp_dealloc*/
(printfunc)proxy_print, /*tp_print*/
0, /*tp_getattr*/
0, /*tp_setattr*/
(cmpfunc)proxy_compare, /*tp_compare*/
(unaryfunc)proxy_repr, /*tp_repr*/
&proxy_as_number, /*tp_as_number*/
&proxy_as_sequence, /*tp_as_sequence*/
&proxy_as_mapping, /*tp_as_mapping*/
0, /*tp_hash*/
(ternaryfunc)0, /*tp_call*/
(unaryfunc)proxy_str, /*tp_str*/
(getattrofunc)proxy_getattr,/*tp_getattro*/
(setattrofunc)proxy_setattr,/*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_GC
|Py_TPFLAGS_CHECKTYPES, /*tp_flags*/
0, /*tp_doc*/
(traverseproc)gc_traverse, /*tp_traverse*/
(inquiry)gc_clear, /*tp_clear*/
};
static PyTypeObject
PyWeakCallableProxy_Type = {
PyObject_HEAD_INIT(NULL)
0,
"weakcallableproxy",
sizeof(PyWeakReference) + PyGC_HEAD_SIZE,
0,
/* methods */
(destructor)weakref_dealloc,/*tp_dealloc*/
(printfunc)proxy_print, /*tp_print*/
0, /*tp_getattr*/
0, /*tp_setattr*/
(cmpfunc)proxy_compare, /*tp_compare*/
(unaryfunc)proxy_repr, /*tp_repr*/
&proxy_as_number, /*tp_as_number*/
&proxy_as_sequence, /*tp_as_sequence*/
&proxy_as_mapping, /*tp_as_mapping*/
0, /*tp_hash*/
(ternaryfunc)proxy_call, /*tp_call*/
(unaryfunc)proxy_str, /*tp_str*/
(getattrofunc)proxy_getattr,/*tp_getattro*/
(setattrofunc)proxy_setattr,/*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_GC
|Py_TPFLAGS_CHECKTYPES, /*tp_flags*/
0, /*tp_doc*/
(traverseproc)gc_traverse, /*tp_traverse*/
(inquiry)gc_clear, /*tp_clear*/
};
static long
getweakrefcount(PyWeakReference *head)
{
long count = 0;
while (head != NULL) {
++count;
head = head->wr_next;
}
return count;
}
static PyObject *
weakref_getweakrefcount(PyObject *self, PyObject *args)
{
PyObject *result = NULL;
PyObject *object;
if (PyArg_ParseTuple(args, "O:getweakrefcount", &object)) {
if (PyType_SUPPORTS_WEAKREFS(object->ob_type)) {
PyWeakReference **list = GET_WEAKREFS_LISTPTR(object);
result = PyInt_FromLong(getweakrefcount(*list));
}
else
result = PyInt_FromLong(0);
}
return result;
}
static PyObject *
weakref_getweakrefs(PyObject *self, PyObject *args)
{
PyObject *result = NULL;
PyObject *object;
if (PyArg_ParseTuple(args, "O:getweakrefs", &object)) {
if (PyType_SUPPORTS_WEAKREFS(object->ob_type)) {
PyWeakReference **list = GET_WEAKREFS_LISTPTR(object);
long count = 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;
}
/* Given the head of an object's list of weak references, extract the
* two callback-less refs (ref and proxy). Used to determine if the
* shared references exist and to determine the back link for newly
* inserted references.
*/
static void
get_basic_refs(PyWeakReference *head,
PyWeakReference **refp, PyWeakReference **proxyp)
{
*refp = NULL;
*proxyp = NULL;
if (head != NULL && head->wr_callback == NULL) {
if (head->ob_type == &PyWeakReference_Type) {
*refp = head;
head = head->wr_next;
}
if (head != NULL && head->wr_callback == NULL) {
*proxyp = head;
head = head->wr_next;
}
}
}
/* Insert 'newref' in the list after 'prev'. Both must be non-NULL. */
static void
insert_after(PyWeakReference *newref, PyWeakReference *prev)
{
newref->wr_prev = prev;
newref->wr_next = prev->wr_next;
if (prev->wr_next != NULL)
prev->wr_next->wr_prev = newref;
prev->wr_next = newref;
}
/* Insert 'newref' at the head of the list; 'list' points to the variable
* that stores the head.
*/
static void
insert_head(PyWeakReference *newref, PyWeakReference **list)
{
PyWeakReference *next = *list;
newref->wr_prev = NULL;
newref->wr_next = next;
if (next != NULL)
next->wr_prev = newref;
*list = newref;
}
static PyObject *
weakref_ref(PyObject *self, PyObject *args)
{
PyObject *object;
PyObject *callback = NULL;
PyWeakReference *result = NULL;
if (PyArg_ParseTuple(args, "O|O:new", &object, &callback)) {
PyWeakReference **list;
PyWeakReference *ref, *proxy;
if (!PyType_SUPPORTS_WEAKREFS(object->ob_type)) {
PyErr_Format(PyExc_TypeError,
"'%s' objects are not weakly referencable",
object->ob_type->tp_name);
return NULL;
}
list = GET_WEAKREFS_LISTPTR(object);
get_basic_refs(*list, &ref, &proxy);
if (callback == NULL) {
/* return existing weak reference if it exists */
result = ref;
Py_XINCREF(result);
}
if (result == NULL) {
result = new_weakref();
if (result != NULL) {
Py_XINCREF(callback);
result->wr_callback = callback;
result->wr_object = object;
if (callback == NULL) {
insert_head(result, list);
}
else {
PyWeakReference *prev = (proxy == NULL) ? ref : proxy;
if (prev == NULL)
insert_head(result, list);
else
insert_after(result, prev);
}
PyObject_GC_Init((PyObject *) result);
}
}
}
return (PyObject *) result;
}
static PyObject *
weakref_proxy(PyObject *self, PyObject *args)
{
PyObject *object;
PyObject *callback = NULL;
PyWeakReference *result = NULL;
if (PyArg_ParseTuple(args, "O|O:new", &object, &callback)) {
PyWeakReference **list;
PyWeakReference *ref, *proxy;
if (!PyType_SUPPORTS_WEAKREFS(object->ob_type)) {
PyErr_Format(PyExc_TypeError,
"'%s' objects are not weakly referencable",
object->ob_type->tp_name);
return NULL;
}
list = GET_WEAKREFS_LISTPTR(object);
get_basic_refs(*list, &ref, &proxy);
if (callback == NULL) {
/* attempt to return an existing weak reference if it exists */
result = proxy;
Py_XINCREF(result);
}
if (result == NULL) {
result = new_weakref();
if (result != NULL) {
PyWeakReference *prev;
if (PyCallable_Check(object))
result->ob_type = &PyWeakCallableProxy_Type;
else
result->ob_type = &PyWeakProxy_Type;
result->wr_object = object;
Py_XINCREF(callback);
result->wr_callback = callback;
if (callback == NULL)
prev = ref;
else
prev = (proxy == NULL) ? ref : proxy;
if (prev == NULL)
insert_head(result, list);
else
insert_after(result, prev);
PyObject_GC_Init((PyObject *) result);
}
}
}
return (PyObject *) result;
}
/* This is the implementation of the PyObject_ClearWeakRefs() function; it
* is installed in the init_weakref() function. It is called by the
* tp_dealloc handler to clear weak references.
*
* This returns true if the object should be deallocated, and false if the
* object is resurrected and deallocation should be aborted.
*
* This iterates through the weak references for 'object' and calls callbacks
* until one resurrects the object, at which point it stops invalidating
* weak references and returns false.
*/
static int
cleanup_helper(PyObject *object)
{
PyWeakReference **list;
if (object == NULL
|| !PyType_SUPPORTS_WEAKREFS(object->ob_type)
|| object->ob_refcnt != 0) {
PyErr_BadInternalCall();
/* not sure what we should return here */
return 1;
}
list = GET_WEAKREFS_LISTPTR(object);
while (*list != NULL) {
PyWeakReference *current = *list;
PyObject *callback = current->wr_callback;
Py_XINCREF(callback);
clear_weakref(current);
if (callback != NULL) {
PyObject *cbresult;
cbresult = PyObject_CallFunction(callback, "O", current);
if (cbresult == NULL)
PyErr_WriteUnraisable(callback);
else
Py_DECREF(cbresult);
Py_DECREF(callback);
}
}
return (object->ob_refcnt > 0 ? 0 : 1);
}
static PyMethodDef
weakref_functions[] = {
{"getweakrefcount", weakref_getweakrefcount, METH_VARARGS,
"getweakrefcount(object) -- return the number of weak references\n"
"to 'object'."},
{"getweakrefs", weakref_getweakrefs, METH_VARARGS,
"getweakrefs(object) -- return a list of all weak reference objects\n"
"that point to 'object'."},
{"proxy", weakref_proxy, METH_VARARGS,
"proxy(object[, callback]) -- create a proxy object that weakly\n"
"references 'object'. 'callback', if given, is called with a\n"
"reference to 'object' when it is about to be finalized."},
{"ref", weakref_ref, METH_VARARGS,
"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'."},
{NULL, NULL, 0, NULL}
};
DL_EXPORT(void)
init_weakref(void)
{
PyObject *m;
PyWeakReference_Type.ob_type = &PyType_Type;
PyWeakProxy_Type.ob_type = &PyType_Type;
PyWeakCallableProxy_Type.ob_type = &PyType_Type;
m = Py_InitModule3("_weakref", weakref_functions,
"Weak-reference support module.");
if (m != NULL) {
PyObject_ClearWeakRefs = cleanup_helper;
Py_INCREF(&PyWeakReference_Type);
PyModule_AddObject(m, "ReferenceType",
(PyObject *) &PyWeakReference_Type);
Py_INCREF(&PyWeakProxy_Type);
PyModule_AddObject(m, "ProxyType",
(PyObject *) &PyWeakProxy_Type);
Py_INCREF(&PyWeakCallableProxy_Type);
PyModule_AddObject(m, "CallableProxyType",
(PyObject *) &PyWeakCallableProxy_Type);
ReferenceError = PyErr_NewException("weakref.ReferenceError",
PyExc_RuntimeError, NULL);
if (ReferenceError != NULL)
PyModule_AddObject(m, "ReferenceError", ReferenceError);
}
}
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