# NanoTimer.java

    /*
    ** Module   : NanoTimer.java
    ** Abstract : Helper class for measuring time intervals
    **
    ** Copyright (c) 2020-2024, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ---------------------------------------Description----------------------------------------
    ** 001 IAS 20200930 Created initial version.
    **     CA  20201003 Allow unchecked exceptions to propagate (otherwise any ConditionException will not be
    **                  caught properly).
    **     CA  20221031 Ensure this is enabled if this is created after the associated mbean is enabled.
    ** 002 AL2 20230216 Added timer method able to return the value of the underlying instrumented code.
    ** 003 HC  20240222 Enabled JMX on FWD Client.
    */

    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program is distributed in the hope that it will be useful,
    ** but WITHOUT ANY WARRANTY; without even the implied warranty of
    ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ** GNU Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
    **   2. No Misrepresentation of Affiliation.
    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
    **     You may not represent yourself for publicity purposes as associated with
    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.jmx;

    import java.util.function.*;

    import com.goldencode.p2j.jmx.FwdServerJMX.TimeStat;

    /** Helper class for measuring time intervals */
    public class NanoTimer
    extends SimpleCounter
    {
       /** start of the operation */
       private long start;

       /**
        * Create and register instance
        * @param    counter
        *           Counter MBean
        * @return   new <code>NanoTimer</code> instance
        */
       public static NanoTimer getInstance(TimeStat counter)
       {
           NanoTimer timer = new NanoTimer(counter::update);
           timer.setEnabler(timer::setEnabled); //prevent GC
           timer.setEnabled(counter.getCounter().isEnabled());
           counter.register(timer.getEnabler());
           return timer;
       }

       /**
        * Constructor
        * @param publish
        *        samples' consumer
        */
       protected NanoTimer(LongConsumer publish)
       {
           super(publish);
       }

       /**
        * Start operation
        */
       public void start()
       {
           start = System.nanoTime();
       }

       /** Stop operation and update counter */
       public void stop()
       {
           update(System.nanoTime() - start);
       }

       /**
        * Execute operation and measure execution time
        * @param r
        *        operation to be executed
        */
       public void timer(Operation r)
       {
           if (!enabled)
           {
               try
               {
                  r.exec();
               }
               catch (RuntimeException re)
               {
                  // unchecked exception propagate as is.  otherwise, we can't process ConditionException.
                  throw re;
               }
               catch (Exception e)
               {
                  throw new RuntimeException(e);
               }
               return;
           }
           start();
           try
           {
              r.exec();
           }
           catch (RuntimeException re)
           {
              // unchecked exception propagate as is.  otherwise, we can't process ConditionException.
              throw re;
           }
           catch (Exception e)
           {
              throw new RuntimeException(e);
           }
           finally
           {
               stop();
           }
       }

       /**
        * Execute operation and measure execution time
        *
        * @param   <T>
        *          The type of the return value for the operation to be executed.
        * @param   r
        *          operation to be executed
        *
        * @return  The result of the operation to be executed
        */
       public <T> T timerWithReturn(ReturningOperation<T> r)
       {
           if (!enabled)
           {
               try
               {
                  return r.exec();
               }
               catch (RuntimeException re)
               {
                  // unchecked exception propagate as is.  otherwise, we can't process ConditionException.
                  throw re;
               }
               catch (Exception e)
               {
                  throw new RuntimeException(e);
               }
           }
           start();
           try
           {
              return r.exec();
           }
           catch (RuntimeException re)
           {
              // unchecked exception propagate as is.  otherwise, we can't process ConditionException.
              throw re;
           }
           catch (Exception e)
           {
              throw new RuntimeException(e);
           }
           finally
           {
               stop();
           }
       }
    }