From 923680f44bac7ca04865c5245ab5d766d6be7ffb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kjist=C3=B3f?= <mrtoth@strongds.hu>
Date: Sun, 27 Nov 2016 19:36:45 +0100
Subject: [PATCH] abandoned my template based approach of tackling code dupe.
 closes #1.

I've decided, that the approach was too complex, you can look at the
code in commit f4eead282f758c17ffdd3c5881a230327da69078, it's some of
the worst template-magic I have ever written and it didn't even work in
that state. now it is handled simply via a bool parameter, the compiler
should optimize it away anyway
---
 thread_pool.hpp | 58 ++++++++++++-------------------------------------
 1 file changed, 14 insertions(+), 44 deletions(-)

diff --git a/thread_pool.hpp b/thread_pool.hpp
index 1648eff..914ba01 100644
--- a/thread_pool.hpp
+++ b/thread_pool.hpp
@@ -52,23 +52,9 @@ class thread_pool
     /* the main loop of the threads */
     void loop();
 
-    class place_front_policy
-    {
-    public:
-        template <typename F, typename... Args>
-        static void place(std::shared_ptr<std::packaged_task<decltype(std::declval<F>()(std::declval<Args>()...))>> task,
-                          std::deque<std::function<void()>>& queue, std::mutex& mu)
-        {
-            {
-                std::lock_guard<std::mutex> lock(mu);
-                queue.emplace_back([task](){ (*task)(); });
-            }
-        }
-    };
-
-    template <typename F, typename... Args, class placement_policy = place_front_policy>
-    auto _add_task_internal(F&& f, Args&&... args) -> std::future<decltype(f(std::forward<Args>(args)...))>;
-
+    template <typename F, typename... Args>
+    auto _add_task_internal(bool front, F&& f, Args&&... args)
+    -> std::future<decltype(f(std::forward<Args>(args)...))>;
 
 public:
 
@@ -86,7 +72,6 @@ public:
     template <typename R> void priority_task(std::packaged_task<R()>&& ) = delete;
 
     /* adding tasks to the queue */
-    // TODO: use template-based policies to deal with priority tasks to avoid code-dupe.
     template <typename F, typename... Args>
     auto add_task(F&& f, Args&&... args) -> std::future<decltype(f(std::forward<Args>(args)...))>;
 
@@ -104,17 +89,22 @@ public:
     /* means of getting information */
     inline size_t get_thread_num() const { return workers.size(); }
     inline size_t get_queue_size() const { return queue.size(); }
-
 };
 
-template <typename F, typename... Args, class placement_policy>
-auto thread_pool::_add_task_internal(F&& f, Args&&... args)
+template <typename F, typename... Args>
+auto thread_pool::_add_task_internal(bool front, F&& f, Args&&... args)
 -> std::future<decltype(f(std::forward<Args>(args)...))>
 {
     auto pckgd_tsk = std::make_shared<std::packaged_task<decltype(f(std::forward<Args>(args)...))()> >
             (std::bind(std::forward<F>(f), std::forward<Args>(args)...));
 
-    placement_policy::place(pckgd_tsk, queue, mu);
+    {
+        std::lock_guard<std::mutex> lock(mu);
+        if (front)
+            queue.emplace_front([pckgd_tsk](){ (*pckgd_tsk)(); });
+        else
+            queue.emplace_back([pckgd_tsk](){ (*pckgd_tsk)(); });
+    }
     cond.notify_one();
 
     return pckgd_tsk->get_future();
@@ -140,34 +130,14 @@ template <typename F, typename... Args>
 auto thread_pool::add_task(F&& f, Args&&... args)
 -> std::future<decltype(f(std::forward<Args>(args)...))>
 {
-    auto pckgd_tsk = std::make_shared<std::packaged_task<decltype(f(std::forward<Args>(args)...))()> >
-            (std::bind(std::forward<F>(f), std::forward<Args>(args)...));
-
-    {
-        std::lock_guard<std::mutex> lock(mu);
-        queue.emplace_back([pckgd_tsk](){ (*pckgd_tsk)(); });
-    }
-    cond.notify_one();
-
-    return pckgd_tsk->get_future();
+    return _add_task_internal(false, std::forward<F>(f), std::forward<Args>(args)...);
 }
 
 template <typename F, typename... Args>
 auto thread_pool::priority_task(F&& f, Args&&... args)
 -> std::future<decltype(f(std::forward<Args>(args)...))>
 {
-    auto pckgd_tsk = std::make_shared<std::packaged_task<decltype(f(std::forward<Args>(args)...))()> >
-            (std::bind(std::forward<F>(f), std::forward<Args>(args)...));
-
-    auto ret_val= pckgd_tsk->get_future();
-
-    {
-        std::lock_guard<std::mutex> lock(mu);
-        queue.emplace_front([pckgd_tsk](){ (*pckgd_tsk)(); });
-    }
-    cond.notify_one();
-
-    return ret_val;
+    return _add_task_internal(true, std::forward<F>(f), std::forward<Args>(args)...);
 }
 
 template <typename R>