Issue 5183 - Provide async interface for FileSystem

src/Thread.h

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 17 matching lines @@
 #else
 #include <pthread.h>
 #endif
 
 namespace AdblockPlus
 {
   class Sync
   {
   public:
     Sync()
-      : set(false)
+      : isSet(false)
     {
     }
+    void Wait()
+    {
+      std::unique_lock<std::mutex> lock(mutex);
+      if (!isSet)
+        cv.wait(lock);
+    }
+
     template<class R = typename std::chrono::seconds::rep,
              class P = std::ratio<1>>
-    void Wait(const std::chrono::duration<R, P>& duration = std::chrono::seconds(20))
+    bool WaitFor(const std::chrono::duration<R, P>& duration = std::chrono::seconds(20))
     {
       std::unique_lock<std::mutex> lock(mutex);
-      while (!set)
-      {
-        if (duration == std::chrono::duration<R>::zero())
-          cv.wait(lock);
-        else
-          cv.wait_for(lock, duration);
-      }
+      if (!isSet)
+        return cv.wait_for(lock, duration) == std::cv_status::no_timeout;
+      return true;
     }

[sergei, 2017/07/03 09:25:56]

Zero seems even less appropriate here but OK, I think it should not be an issue
currently. BTW, what about returning of member `set` from `Wait`?

[hub, 2017/07/04 19:58:27]

I wasn't super thrilled about it either.
Maybe we can have a `WaitFor` that takes the duration and have `Wait` not
timeout.
`WaitFor` will return false if timeout occured.

[sergei, 2017/07/05 10:03:20]

I thought about it too, it actually looks very good.

     void Set(const std::string& err = std::string())
     {
       {
         std::unique_lock<std::mutex> lock(mutex);
-        set = true;
+        isSet = true;
         error = err;
       }
       cv.notify_all();
     }
     std::string GetError()
     {
       std::unique_lock<std::mutex> lock(mutex);
       return error;
     }
   private:
     std::mutex mutex;
     std::condition_variable cv;
-    bool set;

[sergei, 2017/07/03 09:25:55]

would it be better to call it as `isSet`?

[hub, 2017/07/04 19:58:27]

sure

+    bool isSet;
     std::string error;
   };
 
   void Sleep(int millis);
 
   class Mutex
   {
   public:
 #ifdef WIN32
     CRITICAL_SECTION nativeMutex;
@@ skipping 31 matching lines @@
 #ifdef WIN32
     HANDLE nativeThread;
 #else
     pthread_t nativeThread;
 #endif
     bool m_deleteSelfOnFinish;
   };
 }
 
 #endif