Add beast_basics module

modules/beast_basics/threads/beast_CallQueue.cpp

@@ -0,0 +1,166 @@
+/*============================================================================*/
+/*
+  VFLib: https://github.com/vinniefalco/VFLib
+
+  Copyright (C) 2008 by Vinnie Falco <vinnie.falco@gmail.com>
+
+  This library contains portions of other open source products covered by
+  separate licenses. Please see the corresponding source files for specific
+  terms.
+
+  VFLib is provided under the terms of The MIT License (MIT):
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files (the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions:
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+  IN THE SOFTWARE.
+*/
+/*============================================================================*/
+
+CallQueue::CallQueue (String name)
+    : m_name (name)
+{
+}
+
+CallQueue::~CallQueue ()
+{
+    // Someone forget to close the queue.
+    bassert (m_closed.isSignaled ());
+
+    // Can't destroy queue with unprocessed calls.
+    bassert (m_queue.empty ());
+}
+
+bool CallQueue::isAssociatedWithCurrentThread () const
+{
+    return Thread::getCurrentThreadId () == m_id;
+}
+
+// Adds a call to the queue of execution.
+void CallQueue::queuep (Work* c)
+{
+    // If this goes off it means calls are being made after the
+    // queue is closed, and probably there is no one around to
+    // process it.
+    bassert (!m_closed.isSignaled ());
+
+    if (m_queue.push_back (c))
+        signal ();
+}
+
+// Append the Work to the queue. If this call is made from the same
+// thread as the last thread that called synchronize(), then the call
+// will execute synchronously.
+//
+void CallQueue::callp (Work* c)
+{
+    queuep (c);
+
+    // If we are called on the process thread and we are not
+    // recursed into doSynchronize, then process the queue. This
+    // makes calls from the process thread synchronous.
+    //
+    // NOTE: The value of isBeingSynchronized is invalid/volatile unless
+    // this thread is the last process thread.
+    //
+    // NOTE: There is a small window of opportunity where we
+    // might get an undesired synchronization if new thread
+    // calls synchronize() concurrently.
+    //
+    if (isAssociatedWithCurrentThread () &&
+            m_isBeingSynchronized.trySignal ())
+    {
+        doSynchronize ();
+
+        m_isBeingSynchronized.reset ();
+    }
+}
+
+bool CallQueue::synchronize ()
+{
+    bool did_something;
+
+    // Detect recursion into doSynchronize(), and
+    // break ties for concurrent calls atomically.
+    //
+    if (m_isBeingSynchronized.trySignal ())
+    {
+        // Remember this thread.
+        m_id = Thread::getCurrentThreadId ();
+
+        did_something = doSynchronize ();
+
+        m_isBeingSynchronized.reset ();
+    }
+    else
+    {
+        did_something = false;
+    }
+
+    return did_something;
+}
+
+// Can still have pending calls, just can't put new ones in.
+void CallQueue::close ()
+{
+    m_closed.signal ();
+
+    synchronize ();
+}
+
+// Process everything in the queue. The list of pending calls is
+// acquired atomically. New calls may enter the queue while we are
+// processing.
+//
+// Returns true if any functors were called.
+//
+bool CallQueue::doSynchronize ()
+{
+    bool did_something;
+
+    // Reset since we are emptying the queue. Since we loop
+    // until the queue is empty, it is possible for us to exit
+    // this function with an empty queue and signaled state.
+    //
+    reset ();
+
+    Work* call = m_queue.pop_front ();
+
+    if (call)
+    {
+        did_something = true;
+
+        // This method of processing one at a time has the desired
+        // side effect of synchronizing nested calls to us from a functor.
+        //
+        for (;;)
+        {
+            call->operator () ();
+            delete call;
+
+            call = m_queue.pop_front ();
+
+            if (call == 0)
+                break;
+        }
+    }
+    else
+    {
+        did_something = false;
+    }
+
+    return did_something;
+}