jdk/src/java.desktop/share/classes/sun/awt/util/PerformanceLogger.java

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package sun.awt.util;

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 AppContexts will cause
 * confusing results.  For example, if two contexts run
 * simultaneously, the initTime for those will collide
 * and the results may be undefined.
 * <P>
 * To automatically track startup performance in an app
 * use the command-line parameter sun.perflog as follows:<BR>
 * <pre>{@code
 *     -Dsun.perflog[=file:<filename>]
 * }</pre>
 * <BR>
 * where simply using the parameter with no value will enable output
 * to the console and a value of "{@code 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 = System.getProperty("sun.perflog");
        if (perfLoggingProp != null) {
            perfLoggingOn = true;

            // Check if we should use nanoTime
            String perfNanoProp = System.getProperty("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) {
                    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");
                    }
                }
            }
            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.
     */
    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 an application.  This time is
     * later used to analyze the difference between the initial startup
     * time and other events in the system.
     */
    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;.
     */
    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.
     */
    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 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 times.get(index).getTime();
        } else {
            return 0;
        }
    }

    /**
     * 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
     */
    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.
     */
    public static void outputLog() {
        outputLog(logWriter);
    }
}