#ifndef ETHREAD_CLASS #define ETHREAD_CLASS /*****************************************************************************\ * * * Name : ethread (easy thread) * * Author : Chris Koeritz * * * ******************************************************************************* * Copyright (c) 1998-$now By Author. This program is free software; you can * * redistribute it and/or modify it under the terms of the GNU General Public * * License as published by the Free Software Foundation; either version 2 of * * the License or (at your option) any later version. This is online at: * * http://www.fsf.org/copyleft/gpl.html * * Please send any updates to: fred@gruntose.com * \*****************************************************************************/ #include #include #include namespace processes { //! Provides a platform-independent object for adding threads to a program. /*! This greatly simplifies creating and managing threads by hiding all the operating system details. The user just needs to override one virtual function in their derived object to perform the main activity of their thread. The thread can be a one time invocation or it can run periodically. Control over the thread remains in the hands of the program that started it. */ class ethread : public virtual basis::root_object { public: ethread(); //!< creates a single-shot thread object. /*!< the OS-level thread is not started until the start() method is invoked. this constructor creates a thread that will only execute once; when start() is called, the thread starts up and performs its activity. it will then stop. to run it again, start() must be invoked again. however, if the perform_activity() method just keeps running, then the single-shot thread can live as long as needed. it is important for such a thread to periodically check should_exit() to avoid having the program hang-up when it's supposed to be shutting down. */ enum timed_thread_types { TIGHT_INTERVAL, SLACK_INTERVAL }; ethread(int sleep_timer, timed_thread_types how = SLACK_INTERVAL); //!< creates a managed thread object that runs on a periodic interval. /*!< the thread will activate every "sleep_timer" milliseconds. when start() is invoked, the thread's action (via the perform_activity() method) will be performed at regular intervals (using the specified value for "sleep_timer"). the thread will continue activating until the stop() method is called. a faster interval is used internally during sleep periods such that calling stop() will not consume the whole "sleep_timer" period. if the "how" is TIGHT_INTERVAL, then the thread will activate every "sleep_timer" milliseconds, as accurately as possible. if the "how" is SLACK_INTERVAL, then the thread will activate after a delay of "sleep_timer" milliseconds from its last activation. the latter mode allows the thread to consume its entire intended operation time knowing that there will still be slack time between when it is active. the former mode requires the thread to only run for some amount of time less than its "sleep_timer"; otherwise it will hog a lot of the CPU. */ virtual ~ethread(); DEFINE_CLASS_NAME("ethread"); bool start(void *thread_data); //!< causes the thread to start, if it has not already been started. /*!< if the thread has terminated previously, then this will restart the thread. true is returned if the thread could be started. false is returned if the thread could not be started or if it is already running. */ void stop(); //!< tells the thread to shutdown and waits for the shutdown to occur. /*!< this will cause the OS thread to terminate once the current (if any) perform_activity() invocation completes. the thread may be restarted with start(). */ void cancel() { _stop_thread = true; } //!< stops the thread but does not wait until it has terminated. /*!< this is appropriate for use within the perform_activity() method. */ // virtual void pre_thread(); //!< invoked just after after start(), when the OS thread is created. /*!< the call comes in _from_ the thread itself, so the derived method must be thread-safe. */ // virtual void post_thread(); //!< this is invoked just before the thread is to be terminated. /*!< the call also comes in from the thread itself, so the implementation must be thread-safe. */ virtual void perform_activity(void *thread_data) = 0; //!< carries out the main activity of the thread. /*!< this is called repeatedly by the main thread management function and so should return as soon as possible. if it does not return fairly regularly, then the thread shutdown process will not occur until the function exits on its own. */ void exempt_stop(); //!< this special form of stop() does not wait for the thread to exit. /*!< it is required in certain weird OS situations where the thread does not exit properly and stop() would cause an infinite wait. don't use it unless you are SURE that this is the case. */ void reschedule(int delay = 0); //!< causes a periodic thread to activate after "delay" milliseconds from now. /*!< this resets the normal activation period, but after the next activation occurs, the normal activation interval takes over again. */ int sleep_time() const { return _sleep_time; } //!< returns the current periodic thread interval. /*!< this is only meaningful for periodic threads. */ void sleep_time(int new_sleep) { _sleep_time = new_sleep; } //!< adjusts the period for the thread to the "new_sleep" interval. /*!< this is only meaningful for periodic threads. */ // these functions report on the thread state. bool thread_started() const { return _thread_ready; } //!< returns true if the thread has been started. /*!< this does not mean it is necessarily active. */ bool thread_finished() const { return !_thread_ready; } //!< returns true if the thread has exited. /*!< This can happen either by the thread responding to the stop() or cancel() methods or when the thread stops of its own accord. if this returns true, it means that the thread will not start up again unless the user invokes start(). */ bool thread_active() const { return _thread_active; } //!< returns true if the thread is currently performing its activity. /*!< this information is not necessarily relevant even at the point it is returned (because of the nature of multethreading), so don't believe this information for anything important. */ bool should_stop() const { return _stop_thread; } //!< reports whether the thread should stop right now. /*!< this returns true due to an invocation of stop() or cancel(). */ private: bool _thread_ready; //!< is the thread ready to run (or running)? bool _thread_active; //!< is the thread currently performing? bool _stop_thread; //!< true if the thread should stop now. void *_data; //!< holds the thread's link back to whatever. //#ifndef _MSC_VER pthread_t *_handle; //!< thread structure for our thread. //#else //uintptr_t _handle; //!< thread handle for the active thread, or zero. //#endif int _sleep_time; //!< threads perform at roughly this interval. bool _periodic; //!< true if this thread should run repeatedly. timely::time_stamp *_next_activation; //!< the next time perform_activity is called. timed_thread_types _how; //!< how is the period evaluated? // the OS level thread functions. //#ifndef _MSC_VER static void *periodic_thread_driver(void *hidden_pointer); static void *one_shot_thread_driver(void *hidden_pointer); //#else //static void periodic_thread_driver(void *hidden_pointer); //static void one_shot_thread_driver(void *hidden_pointer); //#endif // forbidden. ethread(const ethread &); ethread &operator =(const ethread &); }; } //namespace. #endif