/*
 * Copyright (c) 2008, 2020 Oracle and/or its affiliates. All rights reserved.
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.glassfish.grizzly.http.util;

import java.text.DateFormat;
import java.text.FieldPosition;
import java.text.ParsePosition;
import java.util.Date;

Fast date formatter that caches recently formatted date information and uses it to avoid too-frequent calls to the
underlying formatter. Note: breaks fieldPosition param of format(Date, StringBuffer, FieldPosition). If you care
about the field position, call the underlying DateFormat directly.
Author:
Stan Bailes, Alex Chaffee/**
 * Fast date formatter that caches recently formatted date information and uses it to avoid too-frequent calls to the
 * underlying formatter. Note: breaks fieldPosition param of format(Date, StringBuffer, FieldPosition). If you care
 * about the field position, call the underlying DateFormat directly.
 *
 * @author Stan Bailes
 * @author Alex Chaffee
 **/
public class FastDateFormat extends DateFormat {
    private static final long serialVersionUID = -1L;
    final DateFormat df;
    long lastSec = -1;
    final StringBuffer sb = new StringBuffer();
    final transient FieldPosition fp = new FieldPosition(DateFormat.MILLISECOND_FIELD);

    public FastDateFormat(DateFormat df) {
        this.df = df;
    }

    @Override
    public Date parse(String text, ParsePosition pos) {
        return df.parse(text, pos);
    }

    
Note: breaks functionality of fieldPosition param. Also: there's a bug in SimpleDateFormat with "S" and "SS", use
"SSS" instead if you want a msec field.
/**
     * Note: breaks functionality of fieldPosition param. Also: there's a bug in SimpleDateFormat with "S" and "SS", use
     * "SSS" instead if you want a msec field.
     **/
    @Override
    public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition) {
        long dt = date.getTime();
        long ds = dt / 1000;
        if (ds != lastSec) {
            sb.setLength(0);
            df.format(date, sb, fp);
            lastSec = ds;
        } else {
            // munge current msec into existing string
            int ms = (int) (dt % 1000);
            int pos = fp.getEndIndex();
            int begin = fp.getBeginIndex();
            if (pos > 0) {
                if (pos > begin) {
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                }
                ms /= 10;
                if (pos > begin) {
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                }
                ms /= 10;
                if (pos > begin) {
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                }
            }
        }
        toAppendTo.append(sb.toString());
        return toAppendTo;
    }

    
Note: breaks functionality of fieldPosition param. Also: there's a bug in SimpleDateFormat with "S" and "SS", use
"SSS" instead if you want a msec field.
/**
     * Note: breaks functionality of fieldPosition param. Also: there's a bug in SimpleDateFormat with "S" and "SS", use
     * "SSS" instead if you want a msec field.
     **/
    public StringBuilder format(Date date, StringBuilder toAppendTo, FieldPosition fieldPosition) {
        long dt = date.getTime();
        long ds = dt / 1000;
        if (ds != lastSec) {
            sb.setLength(0);
            df.format(date, sb, fp);
            lastSec = ds;
        } else {
            // munge current msec into existing string
            int ms = (int) (dt % 1000);
            int pos = fp.getEndIndex();
            int begin = fp.getBeginIndex();
            if (pos > 0) {
                if (pos > begin) {
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                }
                ms /= 10;
                if (pos > begin) {
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                }
                ms /= 10;
                if (pos > begin) {
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                }
            }
        }
        toAppendTo.append(sb.toString());
        return toAppendTo;
    }

//    public static void main(String[] args) {
//        String format = "yyyy-MM-dd HH:mm:ss.SSS";
//        if (args.length > 0)
//            format = args[0];
//        SimpleDateFormat sdf = new SimpleDateFormat(format);
//        FastDateFormat fdf = new FastDateFormat(sdf);
//        Date d = new Date();
//
//        d.setTime(1); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(20); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(500); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(543); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(999); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(1050); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(2543); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(12345); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//        d.setTime(12340); System.out.println(fdf.format(d) + '\t' + sdf.format(d));
//
//        final int reps = 100000;
//        {
//            long start = System.currentTimeMillis();
//            for (int i = 0; i < reps; i++) {
//                d.setTime(System.currentTimeMillis());
//                fdf.format(d);
//            }
//            long elap = System.currentTimeMillis() - start;
//            System.out.println("fast: " + elap + " elapsed");
//            System.out.println(fdf.format(d));
//        }
//        {
//            long start = System.currentTimeMillis();
//            for (int i = 0; i < reps; i++) {
//                d.setTime(System.currentTimeMillis());
//                sdf.format(d);
//            }
//            long elap = System.currentTimeMillis() - start;
//            System.out.println("slow: " + elap + " elapsed");
//            System.out.println(sdf.format(d));
//        }
//    }
}