Added the ability to tell a threaded_object that it should restart its thread

upon thread termination.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403669

dlib/threads/threaded_object_extension.cpp

@@ -116,6 +116,73 @@ namespace dlib
         s.broadcast();
     }
 
+// ----------------------------------------------------------------------------------------
+
+    void threaded_object::
+    restart (
+    )
+    {
+        auto_mutex M(m_);
+
+        DLIB_ASSERT(id1 != get_thread_id() || id_valid == false,
+               "\tvoid threaded_object::restart()"
+               << "\n\tYou can NOT call this function from the thread that executes threaded_object::thread"
+               << "\n\tthis: " << this
+        );
+
+        if (is_alive_ == false)
+        {
+            if (create_new_thread<threaded_object,&threaded_object::thread_helper>(*this) == false)
+            {
+                is_running_ = false;
+                throw thread_error();
+            }
+            should_respawn_ = false;
+        }
+        else
+        {
+            should_respawn_ = true;
+        }
+        is_alive_ = true;
+        is_running_ = true;
+        should_stop_ = false;
+        s.broadcast();
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    void threaded_object::
+    set_respawn (
+    )
+    {
+        auto_mutex M(m_);
+
+        DLIB_ASSERT(id1 != get_thread_id() || id_valid == false,
+               "\tvoid threaded_object::set_respawn()"
+               << "\n\tYou can NOT call this function from the thread that executes threaded_object::thread"
+               << "\n\tthis: " << this
+        );
+
+        should_respawn_ = true;
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    bool threaded_object::
+    should_respawn (
+    ) const
+    {
+        auto_mutex M(m_);
+
+        DLIB_ASSERT(id1 != get_thread_id() || id_valid == false,
+               "\tbool threaded_object::should_respawn()"
+               << "\n\tYou can NOT call this function from the thread that executes threaded_object::thread"
+               << "\n\tthis: " << this
+        );
+
+        return should_respawn_;
+    }
+
 // ----------------------------------------------------------------------------------------
 
     void threaded_object::
@@ -149,6 +216,7 @@ namespace dlib
 
         should_stop_ = true;
         is_running_ = false;
+        should_respawn_ = false;
         s.broadcast();
     }
 
@@ -179,10 +247,19 @@ namespace dlib
         id1 = get_thread_id();
         id_valid = true;
 #endif
+        while (true)
+        {
+            m_.lock();
+            should_respawn_ = false;
+            m_.unlock();
 
             thread();
+
             auto_mutex M(m_);
 
+            if (should_respawn_)
+                continue;
+
 #ifdef ENABLE_ASSERTS
             id_valid = false;
 #endif
@@ -191,6 +268,9 @@ namespace dlib
             is_running_ = false;
             should_stop_ = false;
             s.broadcast();
+
+            return;
+        }
     }
 
 // ----------------------------------------------------------------------------------------

dlib/threads/threaded_object_extension.h

@@ -21,6 +21,7 @@ namespace dlib
                 - is_running_ == false
                 - is_alive_ == false 
                 - should_stop_ == false
+                - should_respawn_ == false
 
 #ifdef ENABLE_ASSERTS
                 - id_valid == false 
@@ -31,6 +32,7 @@ namespace dlib
                 - is_running() == is_running_
                 - is_alive() == is_alive_
                 - should_stop() == should_stop_
+                - should_respawn() == should_respawn_
 
 
 #ifdef ENABLE_ASSERTS
@@ -66,6 +68,15 @@ namespace dlib
         void start (
         );
 
+        void restart (
+        );
+
+        void set_respawn (
+        );
+
+        bool should_respawn (
+        ) const;
+
         void pause (
         );
 
@@ -91,6 +102,7 @@ namespace dlib
         bool is_running_;
         bool is_alive_;
         bool should_stop_;
+        bool should_respawn_;
         bool id_valid;
 
         // restricted functions

dlib/threads/threaded_object_extension_abstract.h

@@ -16,6 +16,7 @@ namespace dlib
             INITIAL VALUE
                 - is_running() == false
                 - is_alive() == false 
+                - should_respawn() == false
 
             WHAT THIS OBJECT REPRESENTS
                 This object represents a simple threaded object.  To use it you inherit
@@ -96,6 +97,48 @@ namespace dlib
                     #is_alive() == false and #is_running() == false
         !*/
 
+        void set_respawn (
+        );
+        /*!
+            requires
+                - is not called from this->thread()
+            ensures
+                - #should_respawn() == true
+        !*/
+
+        bool should_respawn (
+        ) const;
+        /*!
+            requires
+                - is not called from this->thread()
+            ensures
+                - returns true if the thread will automatically restart upon termination and
+                  false otherwise.  Note that every time a thread starts it sets should_respawn() 
+                  back to false.  Therefore, a single call to set_respawn() can cause at most
+                  one respawn to occur. 
+        !*/
+
+        void restart (
+        );
+        /*!
+            requires
+                - is not called from this->thread()
+            ensures
+                - This function atomically executes set_respawn() and start().  The precise meaning of this
+                  is defined below.
+                - if (is_alive()) then
+                    - #should_respawn() == true
+                - else
+                    - #should_respawn() == false 
+                - #is_alive() == true
+                - #is_running() == true
+                - #should_stop() == false
+            throws
+                - std::bad_alloc or dlib::thread_error
+                    If either of these exceptions are thrown then 
+                    #is_alive() == false and #is_running() == false
+        !*/
+
         void pause (
         );
         /*!
@@ -113,6 +156,7 @@ namespace dlib
             ensures
                 - #should_stop() == true
                 - #is_running() == false
+                - #should_respawn() == false
         !*/
 
     protected:
@@ -123,8 +167,7 @@ namespace dlib
             requires
                 - is only called from the thread that executes this->thread()
             ensures
-                - if (is_running() == false && should_stop() == false) then
-                    - blocks until (#is_running() == true || #should_stop() == true) 
+                - calls to this function block until (#is_running() == true || #should_stop() == true) 
                 - if (this thread is supposed to terminate) then
                     - returns true
                 - else