py/objpolyiter: Implement instance-polymorphic iterator type.

This allows to have single itertaor type for various internal iterator
types (save rodata space by not having repeating almost-empty type
structures). It works by looking "iternext" method stored in particular
object instance (should be first object field after "base").

py/obj.h

@@ -539,6 +539,7 @@ extern const mp_obj_type_t mp_type_property;
 extern const mp_obj_type_t mp_type_stringio;
 extern const mp_obj_type_t mp_type_bytesio;
 extern const mp_obj_type_t mp_type_reversed;
+extern const mp_obj_type_t mp_type_polymorph_iter;
 
 // Exceptions
 extern const mp_obj_type_t mp_type_BaseException;

py/objpolyiter.c

@@ -0,0 +1,54 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015 Paul Sokolovsky
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <stdlib.h>
+
+#include "py/nlr.h"
+#include "py/runtime.h"
+
+// This is universal iterator type which calls "iternext" method stored in
+// particular object instance. (So, each instance of this time can have its
+// own iteration behavior.) Having this type saves to define type objects
+// for various internal iterator objects.
+
+// Any instance should have these 2 fields at the beginning
+typedef struct _mp_obj_polymorph_iter_t {
+    mp_obj_base_t base;
+    mp_fun_1_t iternext;
+} mp_obj_polymorph_iter_t;
+
+STATIC mp_obj_t polymorph_it_iternext(mp_obj_t self_in) {
+    mp_obj_polymorph_iter_t *self = MP_OBJ_TO_PTR(self_in);
+    // Redirect call to object instance's iternext method
+    return self->iternext(self_in);
+}
+
+const mp_obj_type_t mp_type_polymorph_iter = {
+    { &mp_type_type },
+    .name = MP_QSTR_iterator,
+    .getiter = mp_identity,
+    .iternext = polymorph_it_iternext,
+};

py/py.mk

@@ -122,6 +122,7 @@ PY_O_BASENAME = \
 	objmap.o \
 	objmodule.o \
 	objobject.o \
+	objpolyiter.o \
 	objproperty.o \
 	objnone.o \
 	objnamedtuple.o \