Add libhv and test http client

vendor/libhv/include/hv/singleton.h

@@ -0,0 +1,41 @@
+#ifndef HV_SINGLETON_H_
+#define HV_SINGLETON_H_
+
+#include <mutex>
+
+#define DISABLE_COPY(Class) \
+    Class(const Class&) = delete; \
+    Class& operator=(const Class&) = delete;
+
+#define SINGLETON_DECL(Class) \
+    public: \
+        static Class* instance(); \
+        static void exitInstance(); \
+    private: \
+        DISABLE_COPY(Class) \
+        static Class* s_pInstance; \
+        static std::mutex s_mutex;
+
+#define SINGLETON_IMPL(Class) \
+    Class* Class::s_pInstance = NULL; \
+    std::mutex Class::s_mutex; \
+    Class* Class::instance() { \
+        if (s_pInstance == NULL) { \
+            s_mutex.lock(); \
+            if (s_pInstance == NULL) { \
+                s_pInstance = new Class; \
+            } \
+            s_mutex.unlock(); \
+        } \
+        return s_pInstance; \
+    } \
+    void Class::exitInstance() { \
+        s_mutex.lock(); \
+        if (s_pInstance) {  \
+            delete s_pInstance; \
+            s_pInstance = NULL; \
+        }   \
+        s_mutex.unlock(); \
+    }
+
+#endif // HV_SINGLETON_H_