Created the minicron system. This is a cute little cron like implementation

that allows a program to signal slots on a schedule, possibly a dynamic
schedule.

1 files changed, 226 insertions, 0 deletions

diff --git a/src/minicron.h b/src/minicron.h
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+++ b/src/minicron.h
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+#ifndef BU_MINICRON_H
+#define BU_MINICRON_H
+
+#include "bu/signals.h"
+#include "bu/heap.h"
+#include "bu/fstring.h"
+
+#include <time.h>
+
+namespace Bu
+{
+        /**
+         * A simple cron like system designed to be embedded in any program.  This
+         * class creates a simple cron system that can run any number of jobs at
+         * customizable intervals or schedules.  It does not support some of the
+         * more complex scheduling that some cron systems can do such as load
+         * balancing directly, but this could be done on the job side.
+         *
+         * This system is synchronous, it does not use any threads on it's own, but
+         * it is threadsafe, so a cron thread could be created if desired.
+         *
+         * The operation is fairly simple, jobs can be added at any time, and use
+         * any timer they would like, even custom timers.  When it is time for a
+         * job to be run it signals the slot provided when the job was added.  Every
+         * job slot recieves a handle to the job object so that it may control it's
+         * own lifetime and get information about itself.  In addition, every job
+         * is assigned a unique ID that can be used to control it's operation
+         * at any time.
+         *
+         * By default a job will continually reschedule itself after being run
+         * unless it calls stop() on it's job object, it is removed using
+         * removeJob() on the cron object, or it is added with addJobOnce.
+         */
+        class MiniCron
+        {
+        public:
+                class Job;
+                class Timer;
+                typedef Bu::Signal1<void, Bu::MiniCron::Job &> CronSignal;
+                typedef int JobId;
+
+                MiniCron();
+                virtual ~MiniCron();
+
+                /**
+                 * Tells you if there are jobs registered in the MiniCron.
+                 *@returns true if there are jobs, false otherwise.
+                 */
+                virtual bool hasJobs();
+
+                /**
+                 * If there are jobs, tells you the time the next one will execute.
+                 *@returns The timestamp that the next job will execute at.
+                 */
+                virtual time_t getNextRun();
+
+                /**
+                 * Call this regularly to execute all jobs that should be executed.
+                 * This will loop until all jobs who's run time match the current time
+                 * or are below the current time (we've missed them).
+                 * If there is nothing to run, the runtime of this funcion is constant,
+                 * it is very fast.  Otherwise it executes at log(N) per job run,
+                 * O(N*log(N)).
+                 */
+                virtual void poll();
+
+                /**
+                 * Add a job for repeated scheduling.  Pass in a slot to signal, and a
+                 * Timer object to use to do the scheduling.  This function returns a
+                 * JobId which can be used at a later time to control the execution of
+                 * the job.
+                 */
+                virtual JobId addJob( CronSignal sigJob, const Timer &t );
+
+                /**
+                 * Add a job for one time scheduling.  Pass in a slot to signal, and a
+                 * Timer object to use to schodule the one run of this job.  This
+                 * function returns a JobId which can be used at a later time to control
+                 * the execution of the job.
+                 */
+                virtual JobId addJobOnce( CronSignal sigJob, const Timer &t );
+
+                /**
+                 * Remove a job, preventing all future runs of the job.  If there is no
+                 * job matching the given JobId then nothing will happen.  However, this
+                 * function is relatively expensive compared to the others in this class
+                 * and has a worse case runtime of 2*N*log(N), still not that bad, and
+                 * a O(N*log(N)).
+                 */
+                virtual void removeJob( JobId jid );
+
+                class Timer
+                {
+                public:
+                        Timer();
+                        virtual ~Timer();
+
+                        virtual time_t nextTime()=0;
+                        virtual Timer *clone() const = 0;
+                };
+
+                class TimerInterval : public Timer
+                {
+                public:
+                        TimerInterval( time_t tFirst, time_t tInterval );
+                        virtual ~TimerInterval();
+
+                        virtual time_t nextTime();
+                        virtual Timer *clone() const
+                                { return new TimerInterval( *this ); }
+                private:
+                        time_t tNext;
+                        time_t tInterval;
+                };
+
+                class TimerBasic : public Timer
+                {
+                public:
+                        TimerBasic( const Bu::FString &s );
+                        virtual ~TimerBasic();
+
+                        virtual time_t nextTime();
+                        virtual Timer *clone() const
+                                { return new TimerBasic( *this ); }
+
+                private:
+                        enum Token
+                        {
+                                tokDaily,
+                                tokHourly,
+                                tokWeekly,
+                                tokMonthly,
+                                tokYearly,
+                                valInt,
+                                tokErr,
+                                tokEos
+                        };
+                        Token lex( Bu::FString::const_iterator &i );
+                        int lexInt( Bu::FString::const_iterator &i );
+                        int iVal; //< A temp variable for parsing.
+                        time_t tLast;
+                        Bu::FString sSpec;
+                };
+                
+                class Job
+                {
+                        friend class Bu::MiniCron;
+                public:
+                        Job( JobId jid, bool bRepeat=true );
+                        virtual ~Job();
+
+                        /**
+                         * Execute this job once, increment the runcount and schedule the
+                         * next occurance of it.
+                         */
+                        void run();
+
+                        /**
+                         * Get the time this job will next run.
+                         */
+                        time_t getNextRun();
+
+                        /**
+                         * Compute the time this job will next run.
+                         */
+                        void calcNextRun();
+
+                        /**
+                         * Replace the current job timer with a new one, this will trigger
+                         * a re-schedule.
+                         */
+                        void setTimer( const Timer &t );
+
+                        /**
+                         * Stop execution of this job, never execute this job again.
+                         */
+                        void stop();
+
+                        /**
+                         * Undo a previous stop.  This will cause a job that has been
+                         * stopped or even added with addJobOnce to be set for repeated
+                         * scheduling.
+                         */
+                        void resume();
+
+                        /**
+                         * Get the unique ID of this job.
+                         */
+                        JobId getId();
+
+                        /**
+                         * Get the timestamp this job was created.
+                         */
+                        time_t getTimeCreated();
+
+                        /**
+                         * Get the current run count of this job, how many times it has been
+                         * executed.  This is incremented before the slot is signaled.
+                         */
+                        int getRunCount();
+
+                private:
+                        CronSignal sigJob;
+                        time_t tNextRun;
+                        Timer *pTimer;
+                        bool bContinue;
+                        JobId jid;
+                        time_t tAdded;
+                        int iRunCount;
+                };
+
+        private:
+                struct JobPtrCmp
+                {
+                        bool operator()( const Job *pLeft, const Job *pRight )
+                        {
+                                return pLeft->tNextRun < pRight->tNextRun;
+                        }
+                };
+                typedef Bu::Heap<Job *, JobPtrCmp> JobHeap;
+                JobHeap hJobs;
+                JobId jidNext;
+        };
+};
+
+#endif