Extracted StringReader and StringWriter from JsonParser

Split `Internals/` folder into `Data/`, `Deserialization/`, `Serialization/`

include/ArduinoJson/Data/ListConstIterator.hpp

@@ -0,0 +1,41 @@
+// Copyright Benoit Blanchon 2014-2016
+// MIT License
+//
+// Arduino JSON library
+// https://github.com/bblanchon/ArduinoJson
+// If you like this project, please add a star!
+
+#pragma once
+
+#include "ListNode.hpp"
+
+namespace ArduinoJson {
+namespace Internals {
+
+// A read-only forward itertor for List<T>
+template <typename T>
+class ListConstIterator {
+ public:
+  explicit ListConstIterator(const ListNode<T> *node = NULL) : _node(node) {}
+
+  const T &operator*() const { return _node->content; }
+  const T *operator->() { return &_node->content; }
+
+  bool operator==(const ListConstIterator<T> &other) const {
+    return _node == other._node;
+  }
+
+  bool operator!=(const ListConstIterator<T> &other) const {
+    return _node != other._node;
+  }
+
+  ListConstIterator<T> &operator++() {
+    if (_node) _node = _node->next;
+    return *this;
+  }
+
+ private:
+  const ListNode<T> *_node;
+};
+}
+}