Scheduler.h

/*
             LUFA Library
     Copyright (C) Dean Camera, 2011.

  dean [at] fourwalledcubicle [dot] com
           www.lufa-lib.org
*/

/*
  Copyright 2011  Dean Camera (dean [at] fourwalledcubicle [dot] com)

  Permission to use, copy, modify, distribute, and sell this
  software and its documentation for any purpose is hereby granted
  without fee, provided that the above copyright notice appear in
  all copies and that both that the copyright notice and this
  permission notice and warranty disclaimer appear in supporting
  documentation, and that the name of the author not be used in
  advertising or publicity pertaining to distribution of the
  software without specific, written prior permission.

  The author disclaim all warranties with regard to this
  software, including all implied warranties of merchantability
  and fitness.  In no event shall the author be liable for any
  special, indirect or consequential damages or any damages
  whatsoever resulting from loss of use, data or profits, whether
  in an action of contract, negligence or other tortious action,
  arising out of or in connection with the use or performance of
  this software.
*/

/** \file
 *  \brief Simple round-robbin pseudo-task scheduler.
 *
 *  Simple round-robbin cooperative scheduler for use in basic projects where non real-time tasks need
 *  to be executed. Each task is executed in sequence, and can be enabled or disabled individually or as a group.
 *
 *  \deprecated This module is deprecated and will be removed in a future library release.
 */

/** \defgroup Group_Scheduler Simple Task Scheduler - LUFA/Scheduler/Scheduler.h
 *  \brief Simple round-robbin pseudo-task scheduler.
 *
 *  \deprecated This module is deprecated and will be removed in a future library release.
 *
 *  \section Sec_Dependencies Module Source Dependencies
 *  The following files must be built with any user project that uses this module:
 *    - LUFA/Scheduler/Scheduler.c <i>(Makefile source module name: LUFA_SRC_SCHEDULER)</i>
 *
 *  \section Sec_ModDescription Module Description
 *  Simple round-robbin cooperative scheduler for use in basic projects where non real-time tasks need
 *  to be executed. Each task is executed in sequence, and can be enabled or disabled individually or as a group.
 *
 *  For a task to yield it must \c return, thus each task should have persistent data marked with the \c static keyword.
 *
 *  Each LUFA scheduler task should be written similar to an ISR; it should execute quickly (so that no one task
 *  hogs the processor, preventing another from running before some sort of timeout is exceeded). Unlike normal RTOS
 *  tasks, each LUFA scheduler task is a regular function, and thus must be designed to be called, and designed to
 *  return to the calling scheduler function repeatedly. Data which must be preserved between task calls should be
 *  declared as global or (preferably) as a \c static local variable inside the task.
 *
 *  The scheduler consists of a task list, listing all the tasks which can be executed by the scheduler. Once started,
 *  each task is then called one after another, unless the task is stopped by another running task or interrupt.
 *
 *  Usage Example:
 *  \code
 *      #include <LUFA/Scheduler/Scheduler.h>
 *
 *      TASK(MyTask1); // Task prototype
 *      TASK(MyTask2); // Task prototype
 *
 *      TASK_LIST
 *      {
 *          { .Task = MyTask1, .TaskStatus = TASK_RUN, .GroupID = 1  },
 *          { .Task = MyTask2, .TaskStatus = TASK_RUN, .GroupID = 1  },
 *      }
 *
 *      int main(void)
 *      {
 *          Scheduler_Init();
 *
 *          // Other initialisation here
 *
 *          Scheduler_Start();
 *      }
 *
 *      TASK(MyTask1)
 *      {
 *          // Task implementation here
 *      }
 *
 *      TASK(MyTask2)
 *      {
 *          // Task implementation here
 *      }
 *  \endcode
 *
 *  If desired, the LUFA scheduler <b>does not need to be used</b> in a LUFA powered application. A more conventional
 *  approach to application design can be used, or a proper scheduling RTOS inserted in the place of the LUFA scheduler.
 *  In the case of the former the USB task must be run manually repeatedly to maintain USB communications, and in the
 *  case of the latter a proper RTOS task must be set up to do the same.
 *
 *  @{
 */

#ifndef __SCHEDULER_H__
#define __SCHEDULER_H__

	/* Includes: */
		#include "../Common/Common.h"

	/* Enable C linkage for C++ Compilers: */
		#if defined(__cplusplus)
			extern "C" {
		#endif

	/* Public Interface - May be used in end-application: */
		/* Macros: */
			/** Creates a new scheduler task body or prototype. Should be used in the form:
			 *  \code
			 *      TASK(TaskName); // Prototype
			 *
			 *      TASK(TaskName)
			 *      {
			 *           // Task body
			 *      }
			 *  \endcode
			 */
			#define TASK(name)              void name (void)

			/** Defines a task list array, containing one or more task entries of the type \ref TaskEntry_t. Each task list
			 *  should be encased in curly braces and ended with a comma.
			 *
			 *  Usage Example:
			 *  \code
			 *      TASK_LIST
			 *      {
			 *           { .Task = MyTask1, .TaskStatus = TASK_RUN, .GroupID = 1 },
			 *           // More task entries here
			 *      }
			 *  \endcode
			 */
			#define TASK_LIST               TaskEntry_t Scheduler_TaskList[] =

			/** Constant, giving the maximum delay in scheduler ticks which can be stored in a variable of type
			 *  \ref SchedulerDelayCounter_t.
			 */
			#define TASK_MAX_DELAY          (MAX_DELAYCTR_COUNT - 1)

			/** Task status mode constant, for passing to \ref Scheduler_SetTaskMode() or \ref Scheduler_SetGroupTaskMode(). */
			#define TASK_RUN                true

			/** Task status mode constant, for passing to \ref Scheduler_SetTaskMode() or \ref Scheduler_SetGroupTaskMode(). */
			#define TASK_STOP               false

		/* Pseudo-Function Macros: */
			#if defined(__DOXYGEN__)
				/** Starts the scheduler in its infinite loop, executing running tasks. This should be placed at the end
				 *  of the user application's \c main() function, as it can never return to the calling function.
				 */
				void Scheduler_Start(void);

				/** Initialises the scheduler so that the scheduler functions can be called before the scheduler itself
				 *  is started. This must be executed before any scheduler function calls other than \ref Scheduler_Start(),
				 *  and can be omitted if no such functions could be called before the scheduler is started.
				 */
				void Scheduler_Init(void);
			#else
				#define Scheduler_Start()    Scheduler_GoSchedule(TOTAL_TASKS);
				#define Scheduler_Init()     Scheduler_InitScheduler(TOTAL_TASKS);
			#endif

		/* Type Defines: */
			/** Type define for a pointer to a scheduler task. */
			typedef void (*TaskPtr_t)(void);

			/** Type define for a variable which can hold a tick delay value for the scheduler up to the maximum delay
			 *  possible.
			 */
			typedef uint_least16_t SchedulerDelayCounter_t;

			/** \brief Scheduler Task List Entry Structure.
			 *
			 *  Structure for holding a single task's information in the scheduler task list.
			 */
			typedef struct
			{
				TaskPtr_t     Task;       /**< Pointer to the task to execute. */
				bool          TaskStatus; /**< Status of the task (either TASK_RUN or TASK_STOP). */
				uint_least8_t GroupID;    /**< Group ID of the task so that its status can be changed as a group. */
			} TaskEntry_t;

		/* Global Variables: */
			/** Task entry list, containing the scheduler tasks, task statuses and group IDs. Each entry is of type
			 *  \ref TaskEntry_t and can be manipulated as desired, although it is preferred that the proper Scheduler
			 *  functions should be used instead of direct manipulation.
			 */
			extern TaskEntry_t Scheduler_TaskList[];

			/** Contains the total number of tasks in the task list, irrespective of if the task's status is set to
			 *  \ref TASK_RUN or \ref TASK_STOP.
			 *
			 *  \note This value should be treated as read-only, and never altered in user-code.
			 */
			extern volatile uint_least8_t Scheduler_TotalTasks;

			/**  Contains the current scheduler tick count, for use with the delay functions. If the delay functions
			 *   are used in the user code, this should be incremented each tick period so that the delays can be
			 *   calculated.
			 */
			extern volatile SchedulerDelayCounter_t Scheduler_TickCounter;

		/* Inline Functions: */
			/** Resets the delay counter value to the current tick count. This should be called to reset the period
			 *  for a delay in a task which is dependant on the current tick value.
			 *
			 *  \param[out] DelayCounter  Counter which is storing the starting tick count for a given delay.
			 */
			static inline void Scheduler_ResetDelay(SchedulerDelayCounter_t* const DelayCounter)
			                                        ATTR_NON_NULL_PTR_ARG(1) ATTR_ALWAYS_INLINE;
			static inline void Scheduler_ResetDelay(SchedulerDelayCounter_t* const DelayCounter)
			{
				uint_reg_t CurrentGlobalInt = GetGlobalInterruptMask();
				GlobalInterruptDisable();

				*DelayCounter = Scheduler_TickCounter;

				SetGlobalInterruptMask(CurrentGlobalInt);
			}

		/* Function Prototypes: */
			/** Determines if the given tick delay has elapsed, based on the given delay period and tick counter value.
			 *
			 *  \param[in] Delay         The delay to test for, measured in ticks.
			 *  \param[in] DelayCounter  The counter which is storing the starting tick value for the delay.
			 *
			 *  \return Boolean \c true if the delay has elapsed, \c false otherwise.
			 *
			 *  Usage Example:
			 *  \code
			 *      static SchedulerDelayCounter_t DelayCounter = 10000; // Force immediate run on start-up
			 *
			 *      // Task runs every 10000 ticks, 10 seconds for this demo
			 *      if (Scheduler_HasDelayElapsed(10000, &DelayCounter))
			 *      {
			 *           // Code to execute after delay interval elapsed here
			 *      }
			 *  \endcode
			 */
			bool Scheduler_HasDelayElapsed(const uint_least16_t Delay,
			                               SchedulerDelayCounter_t* const DelayCounter)
			                               ATTR_WARN_UNUSED_RESULT ATTR_NON_NULL_PTR_ARG(2);

			/** Sets the task mode for a given task.
			 *
			 *  \param[in] Task        Name of the task whose status is to be changed.
			 *  \param[in] TaskStatus  New task status for the task (\ref TASK_RUN or \ref TASK_STOP).
			 */
			void Scheduler_SetTaskMode(const TaskPtr_t Task,
			                           const bool TaskStatus);

			/** Sets the task mode for a given task group ID, allowing for an entire group of tasks to have their
			 *  statuses changed at once.
			 *
			 *  \param[in] GroupID     Value of the task group ID whose status is to be changed.
			 *  \param[in] TaskStatus  New task status for tasks in the specified group (\ref TASK_RUN or \ref TASK_STOP).
			 */
			void Scheduler_SetGroupTaskMode(const uint_least8_t GroupID,
			                                const bool TaskStatus);

	/* Private Interface - For use in library only: */
	#if !defined(__DOXYGEN__)
		/* Macros: */
			#define TOTAL_TASKS                       (sizeof(Scheduler_TaskList) / sizeof(TaskEntry_t))
			#define MAX_DELAYCTR_COUNT                UINT_LEAST16_MAX

		/* Inline Functions: */
			static inline void Scheduler_InitScheduler(const uint_least8_t TotalTasks) ATTR_ALWAYS_INLINE;
			static inline void Scheduler_InitScheduler(const uint_least8_t TotalTasks)
			{
				Scheduler_TotalTasks = TotalTasks;
			}

			static inline void Scheduler_GoSchedule(const uint_least8_t TotalTasks)
			                                        ATTR_NO_RETURN ATTR_ALWAYS_INLINE ATTR_DEPRECATED;
			static inline void Scheduler_GoSchedule(const uint_least8_t TotalTasks)
			{
				Scheduler_InitScheduler(TotalTasks);

				for (;;)
				{
					TaskEntry_t* CurrTask = &Scheduler_TaskList[0];

					while (CurrTask != &Scheduler_TaskList[TotalTasks])
					{
						if (CurrTask->TaskStatus == TASK_RUN)
						  CurrTask->Task();

						CurrTask++;
					}
				}
			}
	#endif

	/* Disable C linkage for C++ Compilers: */
		#if defined(__cplusplus)
			}
		#endif

#endif

/** @} */