rippled/modules/beast_basics/threads/beast_ThreadWithCallQueue.h

/*============================================================================*/
/*
  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.
*/
/*============================================================================*/

#ifndef BEAST_THREADWITHCALLQUEUE_BEASTHEADER
#define BEAST_THREADWITHCALLQUEUE_BEASTHEADER

/*============================================================================*/
/**
  An InterruptibleThread with a CallQueue.

  This combines an InterruptibleThread with a CallQueue, allowing functors to
  be queued for asynchronous execution on the thread.

  The thread runs an optional user-defined idle function, which must regularly
  check for an interruption using the InterruptibleThread interface. When an
  interruption is signaled, the idle function returns and the CallQueue is
  synchronized. Then, the idle function is resumed.

  When the ThreadWithCallQueue first starts up, an optional user-defined
  initialization function is executed on the thread. When the thread exits,
  a user-defined exit function may be executed on the thread.

  @see CallQueue

  @ingroup beast_concurrent
*/
class ThreadWithCallQueue
    : public CallQueue
    , private InterruptibleThread::EntryPoint
{
public:
    /** Entry points for a ThreadWithCallQueue.
    */
    class EntryPoints
    {
    public:
        virtual ~EntryPoints () { }

        virtual void threadInit () { }

        virtual void threadExit () { }

        virtual bool threadIdle ()
        {
            bool interrupted = false;

            return interrupted;
        }
    };

    /** Create a thread.

        @param name The name of the InterruptibleThread and CallQueue, used
                    for diagnostics when debugging.
    */
    explicit ThreadWithCallQueue (String name);

    /** Destroy a ThreadWithCallQueue.

        If the thread is still running it is stopped. The destructor blocks
        until the thread exits cleanly.
    */
    ~ThreadWithCallQueue ();

    /** Start the thread.
    */
    void start (EntryPoints* const entryPoints);

    /* Stop the thread.

       Stops the thread and optionally wait until it exits. It is safe to call
       this function at any time and as many times as desired.

       After a call to stop () the CallQueue is closed, and attempts to queue new
       functors will throw a runtime exception. Existing functors will still
       execute.

       Any listeners registered on the CallQueue need to be removed
       before stop is called

       @invariant The caller is not on the associated thread.

       @param wait `true` if the function should wait until the thread exits
                   before returning.
    */

    void stop (bool const wait);

    /**
      Determine if the thread needs interruption.

      Should be called periodically by the idle function. If interruptionPoint
      returns true or throws, it must not be called again until the idle function
      returns and is re-entered.

      @invariant No previous calls to interruptionPoint() made after the idle
                 function entry point returned `true`.

      @return `false` if the idle function may continue, or `true` if the
              idle function must return as soon as possible.
    */
    bool interruptionPoint ();

    /* Interrupts the idle function.
    */
    void interrupt ();

private:
    static void doNothing ();

    void signal ();

    void reset ();

    void doStop ();

    void threadRun ();

private:
    InterruptibleThread m_thread;
    EntryPoints* m_entryPoints;
    bool m_calledStart;
    bool m_calledStop;
    bool m_shouldStop;
    CriticalSection m_mutex;
};

#endif