Added msgpack::type::variant and msgpack::type::variant_ref that is based on boost::variant.

You can convert to those types from any msgpack objects.

example/boost/msgpack_variant_capitalize.cpp

@@ -0,0 +1,102 @@
+// MessagePack for C++ example
+//
+// Copyright (C) 2015 KONDO Takatoshi
+//
+//    Licensed under the Apache License, Version 2.0 (the "License");
+//    you may not use this file except in compliance with the License.
+//    You may obtain a copy of the License at
+//
+//        http://www.apache.org/licenses/LICENSE-2.0
+//
+//    Unless required by applicable law or agreed to in writing, software
+//    distributed under the License is distributed on an "AS IS" BASIS,
+//    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//    See the License for the specific language governing permissions and
+//    limitations under the License.
+//
+
+#include <string>
+#include <sstream>
+#include <iostream>
+#include <algorithm>
+#include <cctype>
+
+#include <msgpack.hpp>
+
+struct user {
+    std::string name;
+    int age;
+    std::string address;
+    MSGPACK_DEFINE(name, age, address);
+};
+
+struct proc:boost::static_visitor<void> {
+    void operator()(std::string& v) const {
+        std::cout << "  match std::string& v" << std::endl;
+        std::cout << "    v: " << v << std::endl;
+        std::cout << "    capitalize" << std::endl;
+        for (std::string::iterator it = v.begin(), end = v.end();
+             it != end;
+             ++it) {
+            *it = std::toupper(*it);
+        }
+    }
+    void operator()(std::vector<msgpack::type::variant>& v) const {
+        std::cout << "match vector (msgpack::type::ARRAY)" << std::endl;
+        std::vector<msgpack::type::variant>::iterator it = v.begin();
+        std::vector<msgpack::type::variant>::const_iterator end = v.end();
+        for (; it != end; ++it) {
+            boost::apply_visitor(*this, *it);
+        }
+    }
+    template <typename T>
+    void operator()(T const&) const {
+        std::cout << "  match others" << std::endl;
+    }
+};
+
+void print(std::string const& buf) {
+    for (std::string::const_iterator it = buf.begin(), end = buf.end();
+         it != end;
+         ++it) {
+        std::cout
+            << std::setw(2)
+            << std::hex
+            << std::setfill('0')
+            << (static_cast<int>(*it) & 0xff)
+            << ' ';
+    }
+    std::cout << std::dec << std::endl;
+}
+
+
+int main() {
+    std::stringstream ss1;
+    user u;
+    u.name = "Takatoshi Kondo";
+    u.age = 42;
+    u.address = "Tokyo, JAPAN";
+
+    std::cout << "Packing object." << std::endl;
+    msgpack::pack(ss1, u);
+    print(ss1.str());
+
+    msgpack::unpacked unp1 = msgpack::unpack(ss1.str().data(), ss1.str().size());
+    msgpack::object const& obj1 = unp1.get();
+    std::cout << "Unpacked msgpack object." << std::endl;
+    std::cout << obj1 << std::endl;
+
+    msgpack::type::variant v = obj1.as<msgpack::type::variant>();
+    std::cout << "Applying proc..." << std::endl;
+    boost::apply_visitor(proc(), v);
+
+    std::stringstream ss2;
+    std::cout << "Packing modified object." << std::endl;
+    msgpack::pack(ss2, v);
+    print(ss2.str());
+
+    msgpack::unpacked unp2 = msgpack::unpack(ss2.str().data(), ss2.str().size());
+    msgpack::object const& obj2 = unp2.get();
+    std::cout << "Modified msgpack object." << std::endl;
+    std::cout << obj2 << std::endl;
+}