/*
 * Copyright 2002 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * 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).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */


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 aribtrary 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 times;
    private static String logFileName = null;
    private static Writer logWriter = null;

    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() {
                        public Object 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(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.
     */
    public static boolean loggingEnabled() {
        return perfLoggingOn;
    }


    /**
     * 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
     */
    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).
     */
    public static void setStartTime(String message) {
        if (loggingEnabled()) {
            long nowTime = getCurrentTime();
            setStartTime(message, nowTime);
        }
    }

    /**
     * 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.
     */
    public static long getStartTime() {
        if (loggingEnabled()) {
            return ((TimeData)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.
     */
    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.
     */
    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.
     */
    public static long getTimeAtIndex(int index) {
        if (loggingEnabled()) {
            return ((TimeData)times.get(index)).getTime();
        } else {
            return 0;
        }
    }

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

    /**
     * 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 = (TimeData)times.get(i);
                        if (td != null) {
                            writer.write(i + " " + td.getMessage() + ": " +
                                         td.getTime() + "\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.
     */
    public static void outputLog() {
        outputLog(logWriter);
    }
}