src/java/org/eclipse/jetty/util/DateCache.java

//
//  ========================================================================
//  Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.util;

import java.text.DateFormatSymbols;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

/* ------------------------------------------------------------ */
/**  Date Format Cache.
 * Computes String representations of Dates and caches
 * the results so that subsequent requests within the same minute
 * will be fast.
 *
 * Only format strings that contain either "ss" or "ss.SSS" are
 * handled.
 *
 * The timezone of the date may be included as an ID with the "zzz"
 * format string or as an offset with the "ZZZ" format string.
 *
 * If consecutive calls are frequently very different, then this
 * may be a little slower than a normal DateFormat.
 *
 * 
 * 
 */

public class DateCache  
{
    public static String DEFAULT_FORMAT="EEE MMM dd HH:mm:ss zzz yyyy";
    private static long __hitWindow=60*60;
    
    private String _formatString;
    private String _tzFormatString;
    private SimpleDateFormat _tzFormat;
    
    private String _minFormatString;
    private SimpleDateFormat _minFormat;

    private String _secFormatString;
    private String _secFormatString0;
    private String _secFormatString1;

    private long _lastMinutes = -1;
    private long _lastSeconds = -1;
    private int _lastMs = -1;
    private String _lastResult = null;

    private Locale _locale	= null;
    private DateFormatSymbols	_dfs	= null;

    /* ------------------------------------------------------------ */
    /** Constructor.
     * Make a DateCache that will use a default format. The default format
     * generates the same results as Date.toString().
     */
    public DateCache()
    {
        this(DEFAULT_FORMAT);
        getFormat().setTimeZone(TimeZone.getDefault());
    }
    
    /* ------------------------------------------------------------ */
    /** Constructor.
     * Make a DateCache that will use the given format
     */
    public DateCache(String format)
    {
        _formatString=format;
        setTimeZone(TimeZone.getDefault());
        
    }
    
    /* ------------------------------------------------------------ */
    public DateCache(String format,Locale l)
    {
        _formatString=format;
        _locale = l;
        setTimeZone(TimeZone.getDefault());       
    }
    
    /* ------------------------------------------------------------ */
    public DateCache(String format,DateFormatSymbols s)
    {
        _formatString=format;
        _dfs = s;
        setTimeZone(TimeZone.getDefault());
    }

    /* ------------------------------------------------------------ */
    /** Set the timezone.
     * @param tz TimeZone
     */
    public synchronized void setTimeZone(TimeZone tz)
    {
        setTzFormatString(tz);        
        if( _locale != null ) 
        {
            _tzFormat=new SimpleDateFormat(_tzFormatString,_locale);
            _minFormat=new SimpleDateFormat(_minFormatString,_locale);
        }
        else if( _dfs != null ) 
        {
            _tzFormat=new SimpleDateFormat(_tzFormatString,_dfs);
            _minFormat=new SimpleDateFormat(_minFormatString,_dfs);
        }
        else 
        {
            _tzFormat=new SimpleDateFormat(_tzFormatString);
            _minFormat=new SimpleDateFormat(_minFormatString);
        }
        _tzFormat.setTimeZone(tz);
        _minFormat.setTimeZone(tz);
        _lastSeconds=-1;
        _lastMinutes=-1;        
    }

    /* ------------------------------------------------------------ */
    public TimeZone getTimeZone()
    {
        return _tzFormat.getTimeZone();
    }
    
    /* ------------------------------------------------------------ */
    /** Set the timezone.
     * @param timeZoneId TimeZoneId the ID of the zone as used by
     * TimeZone.getTimeZone(id)
     */
    public void setTimeZoneID(String timeZoneId)
    {
        setTimeZone(TimeZone.getTimeZone(timeZoneId));
    }
    
    /* ------------------------------------------------------------ */
    private synchronized void setTzFormatString(final  TimeZone tz )
    {
        int zIndex = _formatString.indexOf( "ZZZ" );
        if( zIndex >= 0 )
        {
            String ss1 = _formatString.substring( 0, zIndex );
            String ss2 = _formatString.substring( zIndex+3 );
            int tzOffset = tz.getRawOffset();
            
            StringBuilder sb = new StringBuilder(_formatString.length()+10);
            sb.append(ss1);
            sb.append("'");
            if( tzOffset >= 0 )
                sb.append( '+' );
            else
            {
                tzOffset = -tzOffset;
                sb.append( '-' );
            }
            
            int raw = tzOffset / (1000*60);		// Convert to seconds
            int hr = raw / 60;
            int min = raw % 60;
            
            if( hr < 10 )
                sb.append( '0' );
            sb.append( hr );
            if( min < 10 )
                sb.append( '0' );
            sb.append( min );
            sb.append( '\'' );
            
            sb.append(ss2);
            _tzFormatString=sb.toString();            
        }
        else
            _tzFormatString=_formatString;
        setMinFormatString();
    }

    
    /* ------------------------------------------------------------ */
    private void setMinFormatString()
    {
        int i = _tzFormatString.indexOf("ss.SSS");
        int l = 6;
        if (i>=0)
            throw new IllegalStateException("ms not supported");
        i = _tzFormatString.indexOf("ss");
        l=2;
        
        // Build a formatter that formats a second format string
        String ss1=_tzFormatString.substring(0,i);
        String ss2=_tzFormatString.substring(i+l);
        _minFormatString =ss1+"'ss'"+ss2;
    }

    /* ------------------------------------------------------------ */
    /** Format a date according to our stored formatter.
     * @param inDate 
     * @return Formatted date
     */
    public synchronized String format(Date inDate)
    {
        return format(inDate.getTime());
    }
    
    /* ------------------------------------------------------------ */
    /** Format a date according to our stored formatter.
     * @param inDate 
     * @return Formatted date
     */
    public synchronized String format(long inDate)
    {
        long seconds = inDate / 1000;

        // Is it not suitable to cache?
        if (seconds<_lastSeconds ||
            _lastSeconds>0 && seconds>_lastSeconds+__hitWindow)
        {
            // It's a cache miss
            Date d = new Date(inDate);
            return _tzFormat.format(d);
            
        }
                                          
        // Check if we are in the same second
        // and don't care about millis
        if (_lastSeconds==seconds )
            return _lastResult;

        Date d = new Date(inDate);
        
        // Check if we need a new format string
        long minutes = seconds/60;
        if (_lastMinutes != minutes)
        {
            _lastMinutes = minutes;
            _secFormatString=_minFormat.format(d);

            int i=_secFormatString.indexOf("ss");
            int l=2;
            _secFormatString0=_secFormatString.substring(0,i);
            _secFormatString1=_secFormatString.substring(i+l);
        }

        // Always format if we get here
        _lastSeconds = seconds;
        StringBuilder sb=new StringBuilder(_secFormatString.length());
        sb.append(_secFormatString0);
        int s=(int)(seconds%60);
        if (s<10)
            sb.append('0');
        sb.append(s);
        sb.append(_secFormatString1);
        _lastResult=sb.toString();

                
        return _lastResult;
    }

    /* ------------------------------------------------------------ */
    /** Format to string buffer. 
     * @param inDate Date the format
     * @param buffer StringBuilder
     */
    public void format(long inDate, StringBuilder buffer)
    {
        buffer.append(format(inDate));
    }
    
    /* ------------------------------------------------------------ */
    /** Get the format.
     */
    public SimpleDateFormat getFormat()
    {
        return _minFormat;
    }

    /* ------------------------------------------------------------ */
    public String getFormatString()
    {
        return _formatString;
    }    

    /* ------------------------------------------------------------ */
    public String now()
    {
        long now=System.currentTimeMillis();
        _lastMs=(int)(now%1000);
        return format(now);
    }

    /* ------------------------------------------------------------ */
    public int lastMs()
    {
        return _lastMs;
    }
}