Issue #13521: dict.setdefault() now does only one lookup for the given key, making it "atomic" for many purposes.
Patch by Filip Gruszczyński.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 768351e..27de10d 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -510,27 +510,16 @@
_PyObject_GC_UNTRACK(op);
}
-
/*
-Internal routine to insert a new item into the table.
-Used both by the internal resize routine and by the public insert routine.
-Eats a reference to key and one to value.
-Returns -1 if an error occurred, or 0 on success.
+Internal routine to insert a new item into the table when you have entry object.
+Used by insertdict.
*/
static int
-insertdict(register PyDictObject *mp, PyObject *key, Py_hash_t hash, PyObject *value)
+insertdict_by_entry(register PyDictObject *mp, PyObject *key, Py_hash_t hash,
+ PyDictEntry *ep, PyObject *value)
{
PyObject *old_value;
- register PyDictEntry *ep;
- typedef PyDictEntry *(*lookupfunc)(PyDictObject *, PyObject *, Py_hash_t);
- assert(mp->ma_lookup != NULL);
- ep = mp->ma_lookup(mp, key, hash);
- if (ep == NULL) {
- Py_DECREF(key);
- Py_DECREF(value);
- return -1;
- }
MAINTAIN_TRACKING(mp, key, value);
if (ep->me_value != NULL) {
old_value = ep->me_value;
@@ -553,6 +542,28 @@
return 0;
}
+
+/*
+Internal routine to insert a new item into the table.
+Used both by the internal resize routine and by the public insert routine.
+Eats a reference to key and one to value.
+Returns -1 if an error occurred, or 0 on success.
+*/
+static int
+insertdict(register PyDictObject *mp, PyObject *key, Py_hash_t hash, PyObject *value)
+{
+ register PyDictEntry *ep;
+
+ assert(mp->ma_lookup != NULL);
+ ep = mp->ma_lookup(mp, key, hash);
+ if (ep == NULL) {
+ Py_DECREF(key);
+ Py_DECREF(value);
+ return -1;
+ }
+ return insertdict_by_entry(mp, key, hash, ep, value);
+}
+
/*
Internal routine used by dictresize() to insert an item which is
known to be absent from the dict. This routine also assumes that
@@ -776,39 +787,26 @@
return ep->me_value;
}
-/* CAUTION: PyDict_SetItem() must guarantee that it won't resize the
- * dictionary if it's merely replacing the value for an existing key.
- * This means that it's safe to loop over a dictionary with PyDict_Next()
- * and occasionally replace a value -- but you can't insert new keys or
- * remove them.
- */
-int
-PyDict_SetItem(register PyObject *op, PyObject *key, PyObject *value)
+static int
+dict_set_item_by_hash_or_entry(register PyObject *op, PyObject *key,
+ Py_hash_t hash, PyDictEntry *ep, PyObject *value)
{
register PyDictObject *mp;
- register Py_hash_t hash;
register Py_ssize_t n_used;
- if (!PyDict_Check(op)) {
- PyErr_BadInternalCall();
- return -1;
- }
- assert(key);
- assert(value);
mp = (PyDictObject *)op;
- if (!PyUnicode_CheckExact(key) ||
- (hash = ((PyUnicodeObject *) key)->hash) == -1)
- {
- hash = PyObject_Hash(key);
- if (hash == -1)
- return -1;
- }
assert(mp->ma_fill <= mp->ma_mask); /* at least one empty slot */
n_used = mp->ma_used;
Py_INCREF(value);
Py_INCREF(key);
- if (insertdict(mp, key, hash, value) != 0)
- return -1;
+ if (ep == NULL) {
+ if (insertdict(mp, key, hash, value) != 0)
+ return -1;
+ }
+ else {
+ if (insertdict_by_entry(mp, key, hash, ep, value) != 0)
+ return -1;
+ }
/* If we added a key, we can safely resize. Otherwise just return!
* If fill >= 2/3 size, adjust size. Normally, this doubles or
* quaduples the size, but it's also possible for the dict to shrink
@@ -828,6 +826,36 @@
return dictresize(mp, (mp->ma_used > 50000 ? 2 : 4) * mp->ma_used);
}
+/* CAUTION: PyDict_SetItem() must guarantee that it won't resize the
+ * dictionary if it's merely replacing the value for an existing key.
+ * This means that it's safe to loop over a dictionary with PyDict_Next()
+ * and occasionally replace a value -- but you can't insert new keys or
+ * remove them.
+ */
+int
+PyDict_SetItem(register PyObject *op, PyObject *key, PyObject *value)
+{
+ register Py_hash_t hash;
+
+ if (!PyDict_Check(op)) {
+ PyErr_BadInternalCall();
+ return -1;
+ }
+ assert(key);
+ assert(value);
+ if (PyUnicode_CheckExact(key)) {
+ hash = ((PyUnicodeObject *) key)->hash;
+ if (hash == -1)
+ hash = PyObject_Hash(key);
+ }
+ else {
+ hash = PyObject_Hash(key);
+ if (hash == -1)
+ return -1;
+ }
+ return dict_set_item_by_hash_or_entry(op, key, hash, NULL, value);
+}
+
int
PyDict_DelItem(PyObject *op, PyObject *key)
{
@@ -1797,9 +1825,9 @@
return NULL;
val = ep->me_value;
if (val == NULL) {
- val = failobj;
- if (PyDict_SetItem((PyObject*)mp, key, failobj))
- val = NULL;
+ if (dict_set_item_by_hash_or_entry((PyObject*)mp, key, hash, ep,
+ failobj) == 0)
+ val = failobj;
}
Py_XINCREF(val);
return val;