Add popitem() -- SF patch #102733.

diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 7be1c67de079a8473e8c198b2a0d658d00bdb314..924928fab0c0e547a34d7b9d7ad880939cbb9326 100644 (file)
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -1132,6 +1132,58 @@ dict_clear(register dictobject *mp, PyObject *args)
        return Py_None;
 }
 
+static PyObject *
+dict_popitem(dictobject *mp, PyObject *args)
+{
+       int i = 0;
+       dictentry *ep;
+       PyObject *res;
+
+       if (!PyArg_NoArgs(args))
+               return NULL;
+       if (mp->ma_used == 0) {
+               PyErr_SetString(PyExc_KeyError,
+                               "popitem(): dictionary is empty");
+               return NULL;
+       }
+       /* Set ep to "the first" dict entry with a value.  We abuse the hash
+        * field of slot 0 to hold a search finger:
+        * If slot 0 has a value, use slot 0.
+        * Else slot 0 is being used to hold a search finger,
+        * and we use its hash value as the first index to look.
+        */
+       ep = &mp->ma_table[0];
+       if (ep->me_value == NULL) {
+               i = (int)ep->me_hash;
+               /* The hash field may be uninitialized trash, or it
+                * may be a real hash value, or it may be a legit
+                * search finger, or it may be a once-legit search
+                * finger that's out of bounds now because it
+                * wrapped around or the table shrunk -- simply
+                * make sure it's in bounds now.
+                */
+               if (i >= mp->ma_size || i < 1)
+                       i = 1;  /* skip slot 0 */
+               while ((ep = &mp->ma_table[i])->me_value == NULL) {
+                       i++;
+                       if (i >= mp->ma_size)
+                               i = 1;
+               }
+       }
+       res = PyTuple_New(2);
+       if (res != NULL) {
+               PyTuple_SET_ITEM(res, 0, ep->me_key);
+               PyTuple_SET_ITEM(res, 1, ep->me_value);
+               Py_INCREF(dummy);
+               ep->me_key = dummy;
+               ep->me_value = NULL;
+               mp->ma_used--;
+               assert(mp->ma_table[0].me_value == NULL);
+               mp->ma_table[0].me_hash = i + 1;  /* next place to start */
+       }
+       return res;
+}
+
 static int
 dict_traverse(PyObject *op, visitproc visit, void *arg)
 {
@@ -1167,6 +1219,7 @@ static PyMethodDef mapp_methods[] = {
        {"copy",        (PyCFunction)dict_copy},
        {"get",         (PyCFunction)dict_get,          METH_VARARGS},
        {"setdefault",  (PyCFunction)dict_setdefault,   METH_VARARGS},
+       {"popitem",     (PyCFunction)dict_popitem},
        {NULL,          NULL}           /* sentinel */
 };