Extracted StringReader and StringWriter from JsonParser

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

include/ArduinoJson/Data/JsonVariantAs.hpp

@@ -0,0 +1,45 @@
+// 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
+
+namespace ArduinoJson {
+namespace Internals {
+
+// A metafunction that returns the type of the value returned by
+// JsonVariant::as<T>()
+template <typename T>
+struct JsonVariantAs {
+  typedef T type;
+};
+
+template <>
+struct JsonVariantAs<char*> {
+  typedef const char* type;
+};
+
+template <>
+struct JsonVariantAs<JsonArray> {
+  typedef JsonArray& type;
+};
+
+template <>
+struct JsonVariantAs<const JsonArray> {
+  typedef const JsonArray& type;
+};
+
+template <>
+struct JsonVariantAs<JsonObject> {
+  typedef JsonObject& type;
+};
+
+template <>
+struct JsonVariantAs<const JsonObject> {
+  typedef const JsonObject& type;
+};
+}
+}