py: Rename mp_builtin_id to mp_obj_id and make it public.

py/obj.c

@@ -352,6 +352,24 @@ mp_uint_t mp_get_index(const mp_obj_type_t *type, mp_uint_t len, mp_obj_t index,
     return i;
 }
 
+mp_obj_t mp_obj_id(mp_obj_t o_in) {
+    mp_int_t id = (mp_int_t)o_in;
+    if (!MP_OBJ_IS_OBJ(o_in)) {
+        return mp_obj_new_int(id);
+    } else if (id >= 0) {
+        // Many OSes and CPUs have affinity for putting "user" memories
+        // into low half of address space, and "system" into upper half.
+        // We're going to take advantage of that and return small int
+        // (signed) for such "user" addresses.
+        return MP_OBJ_NEW_SMALL_INT(id);
+    } else {
+        // If that didn't work, well, let's return long int, just as
+        // a (big) positve value, so it will never clash with the range
+        // of small int returned in previous case.
+        return mp_obj_new_int_from_uint((mp_uint_t)id);
+    }
+}
+
 // will raise a TypeError if object has no length
 mp_obj_t mp_obj_len(mp_obj_t o_in) {
     mp_obj_t len = mp_obj_len_maybe(o_in);