Issue 21101: Internal API for dict getitem and setitem where the hash value is known.

Include/dictobject.h

@@ -50,6 +50,8 @@ PyAPI_DATA(PyTypeObject) PyDictValues_Type;
 
 PyAPI_FUNC(PyObject *) PyDict_New(void);
 PyAPI_FUNC(PyObject *) PyDict_GetItem(PyObject *mp, PyObject *key);
+PyAPI_FUNC(PyObject *) _PyDict_GetItem_KnownHash(PyObject *mp, PyObject *key,
+                                       Py_hash_t hash);
 PyAPI_FUNC(PyObject *) PyDict_GetItemWithError(PyObject *mp, PyObject *key);
 PyAPI_FUNC(PyObject *) _PyDict_GetItemIdWithError(PyObject *dp,
                                                   struct _Py_Identifier *key);
@@ -58,6 +60,8 @@ PyAPI_FUNC(PyObject *) PyDict_SetDefault(
     PyObject *mp, PyObject *key, PyObject *defaultobj);
 #endif
 PyAPI_FUNC(int) PyDict_SetItem(PyObject *mp, PyObject *key, PyObject *item);
+PyAPI_FUNC(int) _PyDict_SetItem_KnownHash(PyObject *mp, PyObject *key,
+                                          PyObject *item, Py_hash_t hash);
 PyAPI_FUNC(int) PyDict_DelItem(PyObject *mp, PyObject *key);
 PyAPI_FUNC(void) PyDict_Clear(PyObject *mp);
 PyAPI_FUNC(int) PyDict_Next(

Objects/dictobject.c

@@ -1101,6 +1101,44 @@ PyDict_GetItem(PyObject *op, PyObject *key)
     return *value_addr;
 }
 
+PyObject *
+_PyDict_GetItem_KnownHash(PyObject *op, PyObject *key, Py_hash_t hash)
+{
+    PyDictObject *mp = (PyDictObject *)op;
+    PyDictKeyEntry *ep;
+    PyThreadState *tstate;
+    PyObject **value_addr;
+
+    if (!PyDict_Check(op))
+        return NULL;
+
+    /* We can arrive here with a NULL tstate during initialization: try
+       running "python -Wi" for an example related to string interning.
+       Let's just hope that no exception occurs then...  This must be
+       _PyThreadState_Current and not PyThreadState_GET() because in debug
+       mode, the latter complains if tstate is NULL. */
+    tstate = (PyThreadState*)_Py_atomic_load_relaxed(
+        &_PyThreadState_Current);
+    if (tstate != NULL && tstate->curexc_type != NULL) {
+        /* preserve the existing exception */
+        PyObject *err_type, *err_value, *err_tb;
+        PyErr_Fetch(&err_type, &err_value, &err_tb);
+        ep = (mp->ma_keys->dk_lookup)(mp, key, hash, &value_addr);
+        /* ignore errors */
+        PyErr_Restore(err_type, err_value, err_tb);
+        if (ep == NULL)
+            return NULL;
+    }
+    else {
+        ep = (mp->ma_keys->dk_lookup)(mp, key, hash, &value_addr);
+        if (ep == NULL) {
+            PyErr_Clear();
+            return NULL;
+        }
+    }
+    return *value_addr;
+}
+
 /* Variant of PyDict_GetItem() that doesn't suppress exceptions.
    This returns NULL *with* an exception set if an exception occurred.
    It returns NULL *without* an exception set if the key wasn't present.
@@ -1207,6 +1245,24 @@ PyDict_SetItem(PyObject *op, PyObject *key, PyObject *value)
     return insertdict(mp, key, hash, value);
 }
 
+int
+_PyDict_SetItem_KnownHash(PyObject *op, PyObject *key, PyObject *value,
+                         Py_hash_t hash)
+{
+    PyDictObject *mp;
+
+    if (!PyDict_Check(op)) {
+        PyErr_BadInternalCall();
+        return -1;
+    }
+    assert(key);
+    assert(value);
+    mp = (PyDictObject *)op;
+
+    /* insertdict() handles any resizing that might be necessary */
+    return insertdict(mp, key, hash, value);
+}
+
 int
 PyDict_DelItem(PyObject *op, PyObject *key)
 {