Add libhv and test http client

vendor/libhv/include/hv/hasync.h

@@ -0,0 +1,49 @@
+#ifndef HV_ASYNC_H_
+#define HV_ASYNC_H_
+
+#include "hexport.h"
+#include "hthreadpool.h"
+#include "singleton.h"
+
+namespace hv {
+
+class HV_EXPORT GlobalThreadPool : public HThreadPool {
+    SINGLETON_DECL(GlobalThreadPool)
+protected:
+    GlobalThreadPool() : HThreadPool() {}
+    ~GlobalThreadPool() {}
+};
+
+/*
+ * return a future, calling future.get() will wait task done and return RetType.
+ * async(fn, args...)
+ * async(std::bind(&Class::mem_fn, &obj))
+ * async(std::mem_fn(&Class::mem_fn, &obj))
+ *
+ */
+template<class Fn, class... Args>
+auto async(Fn&& fn, Args&&... args) -> std::future<decltype(fn(args...))> {
+    return GlobalThreadPool::instance()->commit(std::forward<Fn>(fn), std::forward<Args>(args)...);
+}
+
+class async {
+public:
+    static void startup(int min_threads = DEFAULT_THREAD_POOL_MIN_THREAD_NUM,
+                 int max_threads = DEFAULT_THREAD_POOL_MAX_THREAD_NUM,
+                 int max_idle_ms = DEFAULT_THREAD_POOL_MAX_IDLE_TIME) {
+        GlobalThreadPool* gtp = GlobalThreadPool::instance();
+        if (gtp->isStarted()) return;
+        gtp->setMinThreadNum(min_threads);
+        gtp->setMaxThreadNum(max_threads);
+        gtp->setMaxIdleTime(max_idle_ms);
+        gtp->start();
+    }
+
+    static void cleanup() {
+        GlobalThreadPool::exitInstance();
+    }
+};
+
+} // end namespace hv
+
+#endif // HV_ASYNC_H_