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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 *
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package sun.misc;

import java.util.Vector;
import java.io.FileWriter;
import java.io.File;
import java.io.OutputStreamWriter;
import java.io.Writer;

This class is intended to be a central place for the jdk to
log timing events of interest.  There is pre-defined event
of startTime, as well as a general
mechanism of setting arbitrary times in an array.
All unreserved times in the array can be used by callers
in application-defined situations.  The caller is responsible
for setting and getting all times and for doing whatever
analysis is interesting; this class is merely a central container
for those timing values.
Note that, due to the variables in this class being static,
use of particular time values by multiple applets will cause
confusing results.  For example, if plugin runs two applets
simultaneously, the initTime for those applets will collide
and the results may be undefined.

To automatically track startup performance in an app or applet,
use the command-line parameter sun.perflog as follows:

    -Dsun.perflog[=file:]


where simply using the parameter with no value will enable output
to the console and a value of "file:" will cause
that given filename to be created and used for all output.

By default, times are measured using System.currentTimeMillis().  To use
System.nanoTime() instead, add the command-line parameter:

-Dsun.perflog.nano=true



Warning: Use at your own risk!
This class is intended for internal testing
purposes only and may be removed at any time.  More
permanent monitoring and profiling APIs are expected to be
developed for future releases and this class will cease to
exist once those APIs are in place.
Author:
Chet Haase/**
 * This class is intended to be a central place for the jdk to
 * log timing events of interest.  There is pre-defined event
 * of startTime, as well as a general
 * mechanism of setting arbitrary times in an array.
 * All unreserved times in the array can be used by callers
 * in application-defined situations.  The caller is responsible
 * for setting and getting all times and for doing whatever
 * analysis is interesting; this class is merely a central container
 * for those timing values.
 * Note that, due to the variables in this class being static,
 * use of particular time values by multiple applets will cause
 * confusing results.  For example, if plugin runs two applets
 * simultaneously, the initTime for those applets will collide
 * and the results may be undefined.
 * <P>
 * To automatically track startup performance in an app or applet,
 * use the command-line parameter sun.perflog as follows:<BR>
 *     -Dsun.perflog[=file:<filename>]
 * <BR>
 * where simply using the parameter with no value will enable output
 * to the console and a value of "file:<filename>" will cause
 * that given filename to be created and used for all output.
 * <P>
 * By default, times are measured using System.currentTimeMillis().  To use
 * System.nanoTime() instead, add the command-line parameter:<BR>
       -Dsun.perflog.nano=true
 * <BR>
 * <P>
 * <B>Warning: Use at your own risk!</B>
 * This class is intended for internal testing
 * purposes only and may be removed at any time.  More
 * permanent monitoring and profiling APIs are expected to be
 * developed for future releases and this class will cease to
 * exist once those APIs are in place.
 * @author Chet Haase
 */
public class PerformanceLogger {

    // Timing values of global interest
    private static final int START_INDEX    = 0;    // VM start
    private static final int LAST_RESERVED  = START_INDEX;

    private static boolean perfLoggingOn = false;
    private static boolean useNanoTime = false;
    private static Vector<TimeData> times;
    private static String logFileName = null;
    private static Writer logWriter = null;
    private static long baseTime;

    static {
        String perfLoggingProp =
            java.security.AccessController.doPrivileged(
            new sun.security.action.GetPropertyAction("sun.perflog"));
        if (perfLoggingProp != null) {
            perfLoggingOn = true;

            // Check if we should use nanoTime
            String perfNanoProp =
                java.security.AccessController.doPrivileged(
                new sun.security.action.GetPropertyAction("sun.perflog.nano"));
            if (perfNanoProp != null) {
                useNanoTime = true;
            }

            // Now, figure out what the user wants to do with the data
            if (perfLoggingProp.regionMatches(true, 0, "file:", 0, 5)) {
                logFileName = perfLoggingProp.substring(5);
            }
            if (logFileName != null) {
                if (logWriter == null) {
                    java.security.AccessController.doPrivileged(
                    new java.security.PrivilegedAction<Void>() {
                        public Void run() {
                            try {
                                File logFile = new File(logFileName);
                                logFile.createNewFile();
                                logWriter = new FileWriter(logFile);
                            } catch (Exception e) {
                                System.out.println(e + ": Creating logfile " +
                                                   logFileName +
                                                   ".  Log to console");
                            }
                            return null;
                        }
                    });
                }
            }
            if (logWriter == null) {
                logWriter = new OutputStreamWriter(System.out);
            }
        }
        times = new Vector<TimeData>(10);
        // Reserve predefined slots
        for (int i = 0; i <= LAST_RESERVED; ++i) {
            times.add(new TimeData("Time " + i + " not set", 0));
        }
    }

    
Returns status of whether logging is enabled or not.  This is
provided as a convenience method so that users do not have to
perform the same GetPropertyAction check as above to determine whether
to enable performance logging.
/**
     * Returns status of whether logging is enabled or not.  This is
     * provided as a convenience method so that users do not have to
     * perform the same GetPropertyAction check as above to determine whether
     * to enable performance logging.
     */
    public static boolean loggingEnabled() {
        return perfLoggingOn;
    }


    
Internal class used to store time/message data together.
/**
     * Internal class used to store time/message data together.
     */
    static class TimeData {
        String message;
        long time;

        TimeData(String message, long time) {
            this.message = message;
            this.time = time;
        }

        String getMessage() {
            return message;
        }

        long getTime() {
            return time;
        }
    }

    
Return the current time, in millis or nanos as appropriate
/**
     * Return the current time, in millis or nanos as appropriate
     */
    private static long getCurrentTime() {
        if (useNanoTime) {
            return System.nanoTime();
        } else {
            return System.currentTimeMillis();
        }
    }

    
Sets the start time.  Ideally, this is the earliest time available
during the startup of a Java applet or application.  This time is
later used to analyze the difference between the initial startup
time and other events in the system (such as an applet's init time).
/**
     * Sets the start time.  Ideally, this is the earliest time available
     * during the startup of a Java applet or application.  This time is
     * later used to analyze the difference between the initial startup
     * time and other events in the system (such as an applet's init time).
     */
    public static void setStartTime(String message) {
        if (loggingEnabled()) {
            long nowTime = getCurrentTime();
            setStartTime(message, nowTime);
        }
    }

    
Sets the base time, output can then
be displayed as offsets from the base time;.
/**
     * Sets the base time, output can then
     * be displayed as offsets from the base time;.
     */
    public static void setBaseTime(long time) {
        if (loggingEnabled()) {
            baseTime = time;
        }
    }

    
Sets the start time.
This version of the method is
given the time to log, instead of expecting this method to
get the time itself.  This is done in case the time was
recorded much earlier than this method was called.
/**
     * Sets the start time.
     * This version of the method is
     * given the time to log, instead of expecting this method to
     * get the time itself.  This is done in case the time was
     * recorded much earlier than this method was called.
     */
    public static void setStartTime(String message, long time) {
        if (loggingEnabled()) {
            times.set(START_INDEX, new TimeData(message, time));
        }
    }

    
Gets the start time, which should be the time when
the java process started, prior to the VM actually being
loaded.
/**
     * Gets the start time, which should be the time when
     * the java process started, prior to the VM actually being
     * loaded.
     */
    public static long getStartTime() {
        if (loggingEnabled()) {
            return times.get(START_INDEX).getTime();
        } else {
            return 0;
        }
    }

    
Sets the value of a given time and returns the index of the
slot that that time was stored in.
/**
     * Sets the value of a given time and returns the index of the
     * slot that that time was stored in.
     */
    public static int setTime(String message) {
        if (loggingEnabled()) {
            long nowTime = getCurrentTime();
            return setTime(message, nowTime);
        } else {
            return 0;
        }
    }

    
Sets the value of a given time and returns the index of the
slot that that time was stored in.
This version of the method is
given the time to log, instead of expecting this method to
get the time itself.  This is done in case the time was
recorded much earlier than this method was called.
/**
     * Sets the value of a given time and returns the index of the
     * slot that that time was stored in.
     * This version of the method is
     * given the time to log, instead of expecting this method to
     * get the time itself.  This is done in case the time was
     * recorded much earlier than this method was called.
     */
    public static int setTime(String message, long time) {
        if (loggingEnabled()) {
            // times is already synchronized, but we need to ensure that
            // the size used in times.set() is the same used when returning
            // the index of that operation.
            synchronized (times) {
                times.add(new TimeData(message, time));
                return (times.size() - 1);
            }
        } else {
            return 0;
        }
    }

    
Returns time at given index.
/**
     * Returns time at given index.
     */
    public static long getTimeAtIndex(int index) {
        if (loggingEnabled()) {
            return times.get(index).getTime();
        } else {
            return 0;
        }
    }

    
Returns message at given index.
/**
     * Returns message at given index.
     */
    public static String getMessageAtIndex(int index) {
        if (loggingEnabled()) {
            return times.get(index).getMessage();
        } else {
            return null;
        }
    }

    
Outputs all data to parameter-specified Writer object
/**
     * Outputs all data to parameter-specified Writer object
     */
    public static void outputLog(Writer writer) {
        if (loggingEnabled()) {
            try {
                synchronized(times) {
                    for (int i = 0; i < times.size(); ++i) {
                        TimeData td = times.get(i);
                        if (td != null) {
                            writer.write(i + " " + td.getMessage() + ": " +
                                         (td.getTime() - baseTime) + "\n");

                        }
                    }
                }
                writer.flush();
            } catch (Exception e) {
                System.out.println(e + ": Writing performance log to " +
                                   writer);
            }
        }
    }

    
Outputs all data to whatever location the user specified
via sun.perflog command-line parameter.
/**
     * Outputs all data to whatever location the user specified
     * via sun.perflog command-line parameter.
     */
    public static void outputLog() {
        outputLog(logWriter);
    }
}