Source Code for Apache Log4j Core Implementation

Apache Log4j Core Implementation provides the functional components of the logging system. Users are free to create their own plugins and include them in the logging configuration. Apache Log4j Core is a required module to use Apache Log4j.

Bytecode (Java 8) for Apache Log4j Core Implementation is provided in a separate JAR file like log4j-core-2.14.1.jar.

Source Code files for Apache Log4j API are provided in both binary packge like apache-log4j-2.14.1-bin.zip and source package like apache-log4j-2.14.1-src.zip. You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j Core Implementation 2.14.1 below.

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org/apache/logging/log4j/core/util/datetime/FixedDateFormat.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.logging.log4j.core.util.datetime;

import org.apache.logging.log4j.core.time.Instant;

import java.util.Arrays;
import java.util.Calendar;
import java.util.Objects;
import java.util.TimeZone;
import java.util.concurrent.TimeUnit;

/**
 * Custom time formatter that trades flexibility for performance. This formatter only supports the date patterns defined
 * in {@link FixedFormat}. For any other date patterns use {@link FastDateFormat}.
 * <p>
 * Related benchmarks: /log4j-perf/src/main/java/org/apache/logging/log4j/perf/jmh/TimeFormatBenchmark.java and
 * /log4j-perf/src/main/java/org/apache/logging/log4j/perf/jmh/ThreadsafeDateFormatBenchmark.java
 * </p>
 */
public class FixedDateFormat {

    /**
     * Enumeration over the supported date/time format patterns.
     * <p>
     * Package protected for unit tests.
     * </p>
     */
    public enum FixedFormat {
        
        /**
         * ABSOLUTE time format: {@code "HH:mm:ss,SSS"}.
         */
        ABSOLUTE("HH:mm:ss,SSS", null, 0, ':', 1, ',', 1, 3, null),
        /**
         * ABSOLUTE time format with microsecond precision: {@code "HH:mm:ss,nnnnnn"}.
         */
        ABSOLUTE_MICROS("HH:mm:ss,nnnnnn", null, 0, ':', 1, ',', 1, 6, null),
        /**
         * ABSOLUTE time format with nanosecond precision: {@code "HH:mm:ss,nnnnnnnnn"}.
         */
        ABSOLUTE_NANOS("HH:mm:ss,nnnnnnnnn", null, 0, ':', 1, ',', 1, 9, null),

        /**
         * ABSOLUTE time format variation with period separator: {@code "HH:mm:ss.SSS"}.
         */
        ABSOLUTE_PERIOD("HH:mm:ss.SSS", null, 0, ':', 1, '.', 1, 3, null),

        /**
         * COMPACT time format: {@code "yyyyMMddHHmmssSSS"}.
         */
        COMPACT("yyyyMMddHHmmssSSS", "yyyyMMdd", 0, ' ', 0, ' ', 0, 3, null),

        /**
         * DATE_AND_TIME time format: {@code "dd MMM yyyy HH:mm:ss,SSS"}.
         */
        DATE("dd MMM yyyy HH:mm:ss,SSS", "dd MMM yyyy ", 0, ':', 1, ',', 1, 3, null),

        /**
         * DATE_AND_TIME time format variation with period separator: {@code "dd MMM yyyy HH:mm:ss.SSS"}.
         */
        DATE_PERIOD("dd MMM yyyy HH:mm:ss.SSS", "dd MMM yyyy ", 0, ':', 1, '.', 1, 3, null),

        /**
         * DEFAULT time format: {@code "yyyy-MM-dd HH:mm:ss,SSS"}.
         */
        DEFAULT("yyyy-MM-dd HH:mm:ss,SSS", "yyyy-MM-dd ", 0, ':', 1, ',', 1, 3, null),
        /**
         * DEFAULT time format with microsecond precision: {@code "yyyy-MM-dd HH:mm:ss,nnnnnn"}.
         */
        DEFAULT_MICROS("yyyy-MM-dd HH:mm:ss,nnnnnn", "yyyy-MM-dd ", 0, ':', 1, ',', 1, 6, null),
        /**
         * DEFAULT time format with nanosecond precision: {@code "yyyy-MM-dd HH:mm:ss,nnnnnnnnn"}.
         */
        DEFAULT_NANOS("yyyy-MM-dd HH:mm:ss,nnnnnnnnn", "yyyy-MM-dd ", 0, ':', 1, ',', 1, 9, null),

        /**
         * DEFAULT time format variation with period separator: {@code "yyyy-MM-dd HH:mm:ss.SSS"}.
         */
        DEFAULT_PERIOD("yyyy-MM-dd HH:mm:ss.SSS", "yyyy-MM-dd ", 0, ':', 1, '.', 1, 3, null),

        /**
         * ISO8601_BASIC time format: {@code "yyyyMMdd'T'HHmmss,SSS"}.
         */
        ISO8601_BASIC("yyyyMMdd'T'HHmmss,SSS", "yyyyMMdd'T'", 2, ' ', 0, ',', 1, 3, null),

        /**
         * ISO8601_BASIC time format: {@code "yyyyMMdd'T'HHmmss.SSS"}.
         */
        ISO8601_BASIC_PERIOD("yyyyMMdd'T'HHmmss.SSS", "yyyyMMdd'T'", 2, ' ', 0, '.', 1, 3, null),

        /**
         * ISO8601 time format: {@code "yyyy-MM-dd'T'HH:mm:ss,SSS"}.
         */
        ISO8601("yyyy-MM-dd'T'HH:mm:ss,SSS", "yyyy-MM-dd'T'", 2, ':', 1, ',', 1, 3, null),

// TODO Do we even want a format without seconds?
//        /**
//         * ISO8601_OFFSET_DATE_TIME time format: {@code "yyyy-MM-dd'T'HH:mmXXX"}.
//         */
//        // Would need work in org.apache.logging.log4j.core.util.datetime.FixedDateFormat.writeTime(int, char[], int)
//        ISO8601_OFFSET_DATE_TIME("yyyy-MM-dd'T'HH:mmXXX", "yyyy-MM-dd'T'", 2, ':', 1, ' ', 0, 0, FixedTimeZoneFormat.XXX),

        /**
         * ISO8601 time format: {@code "yyyy-MM-dd'T'HH:mm:ss,SSSX"} with a time zone like {@code -07}.
         */
        ISO8601_OFFSET_DATE_TIME_HH("yyyy-MM-dd'T'HH:mm:ss,SSSX", "yyyy-MM-dd'T'", 2, ':', 1, ',', 1, 3, FixedTimeZoneFormat.HH),

        /**
         * ISO8601 time format: {@code "yyyy-MM-dd'T'HH:mm:ss,SSSXX"} with a time zone like {@code -0700}.
         */
        ISO8601_OFFSET_DATE_TIME_HHMM("yyyy-MM-dd'T'HH:mm:ss,SSSXX", "yyyy-MM-dd'T'", 2, ':', 1, ',', 1, 3, FixedTimeZoneFormat.HHMM),

        /**
         * ISO8601 time format: {@code "yyyy-MM-dd'T'HH:mm:ss,SSSXXX"} with a time zone like {@code -07:00}.
         */
        ISO8601_OFFSET_DATE_TIME_HHCMM("yyyy-MM-dd'T'HH:mm:ss,SSSXXX", "yyyy-MM-dd'T'", 2, ':', 1, ',', 1, 3, FixedTimeZoneFormat.HHCMM),

        /**
         * ISO8601 time format: {@code "yyyy-MM-dd'T'HH:mm:ss.SSS"}.
         */
        ISO8601_PERIOD("yyyy-MM-dd'T'HH:mm:ss.SSS", "yyyy-MM-dd'T'", 2, ':', 1, '.', 1, 3, null),

        /**
         * ISO8601 time format with support for microsecond precision: {@code "yyyy-MM-dd'T'HH:mm:ss.nnnnnn"}.
         */
        ISO8601_PERIOD_MICROS("yyyy-MM-dd'T'HH:mm:ss.nnnnnn", "yyyy-MM-dd'T'", 2, ':', 1, '.', 1, 6, null);

        private static final String DEFAULT_SECOND_FRACTION_PATTERN = "SSS";
        private static final int MILLI_FRACTION_DIGITS = DEFAULT_SECOND_FRACTION_PATTERN.length();
        private static final char SECOND_FRACTION_PATTERN = 'n';

        private final String pattern;
        private final String datePattern;
        private final int escapeCount;
        private final char timeSeparatorChar;
        private final int timeSeparatorLength;
        private final char millisSeparatorChar;
        private final int millisSeparatorLength;
        private final int secondFractionDigits;
        private final FixedTimeZoneFormat fixedTimeZoneFormat;

        FixedFormat(final String pattern, final String datePattern, final int escapeCount, final char timeSeparator,
                    final int timeSepLength, final char millisSeparator, final int millisSepLength,
                    final int secondFractionDigits, final FixedTimeZoneFormat timeZoneFormat) {
            this.timeSeparatorChar = timeSeparator;
            this.timeSeparatorLength = timeSepLength;
            this.millisSeparatorChar = millisSeparator;
            this.millisSeparatorLength = millisSepLength;
            this.pattern = Objects.requireNonNull(pattern);
            this.datePattern = datePattern; // may be null
            this.escapeCount = escapeCount;
            this.secondFractionDigits = secondFractionDigits;
            this.fixedTimeZoneFormat = timeZoneFormat;
        }

        /**
         * Returns the full pattern.
         *
         * @return the full pattern
         */
        public String getPattern() {
            return pattern;
        }

        /**
         * Returns the date part of the pattern.
         *
         * @return the date part of the pattern
         */
        public String getDatePattern() {
            return datePattern;
        }

        /**
         * Returns the FixedFormat with the name or pattern matching the specified string or {@code null} if not found.
         *
         * @param nameOrPattern the name or pattern to find a FixedFormat for
         * @return the FixedFormat with the name or pattern matching the specified string
         */
        public static FixedFormat lookup(final String nameOrPattern) {
            for (final FixedFormat type : FixedFormat.values()) {
                if (type.name().equals(nameOrPattern) || type.getPattern().equals(nameOrPattern)) {
                    return type;
                }
            }
            return null;
        }

        static FixedFormat lookupIgnoringNanos(final String pattern) {
            final int[] nanoRange = nanoRange(pattern);
            final int nanoStart = nanoRange[0];
            final int nanoEnd = nanoRange[1];
            if (nanoStart > 0) {
                final String subPattern = pattern.substring(0, nanoStart) + DEFAULT_SECOND_FRACTION_PATTERN
                        + pattern.substring(nanoEnd, pattern.length());
                for (final FixedFormat type : FixedFormat.values()) {
                    if (type.getPattern().equals(subPattern)) {
                        return type;
                    }
                }
            }
            return null;
        }

        private final static int[] EMPTY_RANGE = { -1, -1 };
        
        /**
         * @return int[0] start index inclusive; int[1] end index exclusive
         */
        private static int[] nanoRange(final String pattern) {
            final int indexStart = pattern.indexOf(SECOND_FRACTION_PATTERN);
            int indexEnd = -1;
            if (indexStart >= 0) {
                indexEnd = pattern.indexOf('Z', indexStart);
                indexEnd = indexEnd < 0 ? pattern.indexOf('X', indexStart) : indexEnd;
                indexEnd = indexEnd < 0 ? pattern.length() : indexEnd; 
                for (int i = indexStart + 1; i < indexEnd; i++) {
                    if (pattern.charAt(i) != SECOND_FRACTION_PATTERN) {
                        return EMPTY_RANGE;
                    }
                }
            }
            return new int [] {indexStart, indexEnd};
        }

        /**
         * Returns the length of the resulting formatted date and time strings.
         *
         * @return the length of the resulting formatted date and time strings
         */
        public int getLength() {
            return pattern.length() - escapeCount;
        }

        /**
         * Returns the length of the date part of the resulting formatted string.
         *
         * @return the length of the date part of the resulting formatted string
         */
        public int getDatePatternLength() {
            return getDatePattern() == null ? 0 : getDatePattern().length() - escapeCount;
        }

        /**
         * Returns the {@code FastDateFormat} object for formatting the date part of the pattern or {@code null} if the
         * pattern does not have a date part.
         *
         * @return the {@code FastDateFormat} object for formatting the date part of the pattern or {@code null}
         */
        public FastDateFormat getFastDateFormat() {
            return getFastDateFormat(null);
        }

        /**
         * Returns the {@code FastDateFormat} object for formatting the date part of the pattern or {@code null} if the
         * pattern does not have a date part.
         *
         * @param tz the time zone to use
         * @return the {@code FastDateFormat} object for formatting the date part of the pattern or {@code null}
         */
        public FastDateFormat getFastDateFormat(final TimeZone tz) {
            return getDatePattern() == null ? null : FastDateFormat.getInstance(getDatePattern(), tz);
        }

        /**
         * Returns the number of digits specifying the fraction of the second to show
         * @return 3 for millisecond precision, 6 for microsecond precision or 9 for nanosecond precision
         */
        public int getSecondFractionDigits() {
            return secondFractionDigits;
        }

        /**
         * Returns the optional time zone format.
         * @return the optional time zone format, may be null.
         */
        public FixedTimeZoneFormat getFixedTimeZoneFormat() {
            return fixedTimeZoneFormat;
        }
    }

    private static final char NONE = (char) 0;

    /**
     * Fixed time zone formats. The enum names are symbols from Java's <a href=
     * "https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html">DateTimeFormatter</a>.
     * 
     * @see <a href=
     * "https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html">DateTimeFormatter</a>
     */
    public enum FixedTimeZoneFormat {

        /**
         * Offset like {@code -07}.
         */
        HH(NONE, false, 3),

        /**
         * Offset like {@code -0700}.
         */
        HHMM(NONE, true, 5), 
        
        /** 
         * Offset like {@code -07:00}.
         */
        HHCMM(':', true, 6);
        
        private FixedTimeZoneFormat() {
            this(NONE, true, 4);
        }

        private FixedTimeZoneFormat(final char timeSeparatorChar, final boolean minutes, final int length) {
            this.timeSeparatorChar = timeSeparatorChar;
            this.timeSeparatorCharLen = timeSeparatorChar != NONE ? 1 : 0;
            this.useMinutes = minutes;
            this.length = length;
        }

        private final char timeSeparatorChar;
        private final int timeSeparatorCharLen;
        private final boolean useMinutes;
        // The length includes 1 for the leading sign 
        private final int length;

        public int getLength() {
            return length;
        }

        // Profiling showed this method is important to log4j performance. Modify with care!
        // 262 bytes (will be inlined when hot enough: <= -XX:FreqInlineSize=325 bytes on Linux)
        private int write(final int offset, final char[] buffer, int pos) {
            // This method duplicates part of writeTime()

            buffer[pos++] = offset < 0 ? '-' : '+';
            final int absOffset = Math.abs(offset);
            final int hours = absOffset / 3600000;
            int ms = absOffset - (3600000 * hours);

            // Hour
            int temp = hours / 10;
            buffer[pos++] = ((char) (temp + '0'));

            // Do subtract to get remainder instead of doing % 10
            buffer[pos++] = ((char) (hours - 10 * temp + '0'));

            // Minute
            if (useMinutes) {
                buffer[pos] = timeSeparatorChar;
                pos += timeSeparatorCharLen;
                final int minutes = ms / 60000;
                ms -= 60000 * minutes;

                temp = minutes / 10;
                buffer[pos++] = ((char) (temp + '0'));

                // Do subtract to get remainder instead of doing % 10
                buffer[pos++] = ((char) (minutes - 10 * temp + '0'));
            }
            return pos;
        }

    }

    private final FixedFormat fixedFormat;
    private final TimeZone timeZone;
    private final int length;
    private final int secondFractionDigits;
    private final FastDateFormat fastDateFormat; // may be null
    private final char timeSeparatorChar;
    private final char millisSeparatorChar;
    private final int timeSeparatorLength;
    private final int millisSeparatorLength;
    private final FixedTimeZoneFormat fixedTimeZoneFormat;

    private volatile long midnightToday;
    private volatile long midnightTomorrow;
    private final int[] dstOffsets = new int[25];

    // cachedDate does not need to be volatile because
    // there is a write to a volatile field *after* cachedDate is modified,
    // and there is a read from a volatile field *before* cachedDate is read.
    // The Java memory model guarantees that because of the above,
    // changes to cachedDate in one thread are visible to other threads.
    // See http://g.oswego.edu/dl/jmm/cookbook.html
    private char[] cachedDate; // may be null
    private int dateLength;

    /**
     * Constructs a FixedDateFormat for the specified fixed format.
     * <p>
     * Package protected for unit tests.
     *
     * @param fixedFormat the fixed format
     * @param tz time zone
     */
    FixedDateFormat(final FixedFormat fixedFormat, final TimeZone tz) {
        this(fixedFormat, tz, fixedFormat.getSecondFractionDigits());
    }

    /**
     * Constructs a FixedDateFormat for the specified fixed format.
     * <p>
     * Package protected for unit tests.
     * </p>
     *
     * @param fixedFormat the fixed format
     * @param tz time zone
     * @param secondFractionDigits the number of digits specifying the fraction of the second to show
     */
    FixedDateFormat(final FixedFormat fixedFormat, final TimeZone tz, final int secondFractionDigits) {
        this.fixedFormat = Objects.requireNonNull(fixedFormat);
        this.timeZone = Objects.requireNonNull(tz);
        this.timeSeparatorChar = fixedFormat.timeSeparatorChar;
        this.timeSeparatorLength = fixedFormat.timeSeparatorLength;
        this.millisSeparatorChar = fixedFormat.millisSeparatorChar;
        this.millisSeparatorLength = fixedFormat.millisSeparatorLength;
        this.fixedTimeZoneFormat = fixedFormat.fixedTimeZoneFormat; // may be null
        this.length = fixedFormat.getLength();
        this.secondFractionDigits = Math.max(1, Math.min(9, secondFractionDigits));
        this.fastDateFormat = fixedFormat.getFastDateFormat(tz);
    }

    public static FixedDateFormat createIfSupported(final String... options) {
        if (options == null || options.length == 0 || options[0] == null) {
            return new FixedDateFormat(FixedFormat.DEFAULT, TimeZone.getDefault());
        }
        final TimeZone tz;
        if (options.length > 1) {
            if (options[1] != null) {
                tz = TimeZone.getTimeZone(options[1]);
            } else {
                tz = TimeZone.getDefault();
            }
        } else {
            tz = TimeZone.getDefault();
        }

        final String option0 = options[0];
        final FixedFormat withNanos = FixedFormat.lookupIgnoringNanos(option0);
        if (withNanos != null) {
            final int[] nanoRange = FixedFormat.nanoRange(option0);
            final int nanoStart = nanoRange[0];
            final int nanoEnd = nanoRange[1];
            final int secondFractionDigits = nanoEnd - nanoStart;
            return new FixedDateFormat(withNanos, tz, secondFractionDigits);
        }
        final FixedFormat type = FixedFormat.lookup(option0);
        return type == null ? null : new FixedDateFormat(type, tz);
    }

    /**
     * Returns a new {@code FixedDateFormat} object for the specified {@code FixedFormat} and a {@code TimeZone.getDefault()} TimeZone.
     *
     * @param format the format to use
     * @return a new {@code FixedDateFormat} object
     */
    public static FixedDateFormat create(final FixedFormat format) {
        return new FixedDateFormat(format, TimeZone.getDefault());
    }

    /**
     * Returns a new {@code FixedDateFormat} object for the specified {@code FixedFormat} and TimeZone.
     *
     * @param format the format to use
     * @param tz the time zone to use
     * @return a new {@code FixedDateFormat} object
     */
    public static FixedDateFormat create(final FixedFormat format, final TimeZone tz) {
        return new FixedDateFormat(format, tz != null ? tz : TimeZone.getDefault());
    }

    /**
     * Returns the full pattern of the selected fixed format.
     *
     * @return the full date-time pattern
     */
    public String getFormat() {
        return fixedFormat.getPattern();
    }

    /**
     * Returns the time zone.
     *
     * @return the time zone
     */
    public TimeZone getTimeZone() {
        return timeZone;
    }

    /**
     * <p>Returns the number of milliseconds since midnight in the time zone that this {@code FixedDateFormat}
     * was constructed with for the specified currentTime.</p>
     * <p>As a side effect, this method updates the cached formatted date and the cached date demarcation timestamps
     * when the specified current time is outside the previously set demarcation timestamps for the start or end
     * of the current day.</p>
     * @param currentTime the current time in millis since the epoch
     * @return the number of milliseconds since midnight for the specified time
     */
    // Profiling showed this method is important to log4j performance. Modify with care!
    // 30 bytes (allows immediate JVM inlining: <= -XX:MaxInlineSize=35 bytes)
    public long millisSinceMidnight(final long currentTime) {
        if (currentTime >= midnightTomorrow || currentTime < midnightToday) {
            updateMidnightMillis(currentTime);
        }
        return currentTime - midnightToday;
    }

    private void updateMidnightMillis(final long now) {
        if (now >= midnightTomorrow || now < midnightToday) {
            synchronized (this) {
                updateCachedDate(now);
                midnightToday = calcMidnightMillis(now, 0);
                midnightTomorrow = calcMidnightMillis(now, 1);

                updateDaylightSavingTime();
            }
        }
    }

    private long calcMidnightMillis(final long time, final int addDays) {
        final Calendar cal = Calendar.getInstance(timeZone);
        cal.setTimeInMillis(time);
        cal.set(Calendar.HOUR_OF_DAY, 0);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);
        cal.set(Calendar.MILLISECOND, 0);
        cal.add(Calendar.DATE, addDays);
        return cal.getTimeInMillis();
    }

    private void updateDaylightSavingTime() {
        Arrays.fill(dstOffsets, 0);
        final int ONE_HOUR = (int) TimeUnit.HOURS.toMillis(1);
        if (timeZone.getOffset(midnightToday) != timeZone.getOffset(midnightToday + 23 * ONE_HOUR)) {
            for (int i = 0; i < dstOffsets.length; i++) {
                final long time = midnightToday + i * ONE_HOUR;
                dstOffsets[i] = timeZone.getOffset(time) - timeZone.getRawOffset();
            }
            if (dstOffsets[0] > dstOffsets[23]) { // clock is moved backwards.
                // we obtain midnightTonight with Calendar.getInstance(TimeZone), so it already includes raw offset
                for (int i = dstOffsets.length - 1; i >= 0; i--) {
                    dstOffsets[i] -= dstOffsets[0]; //
                }
            }
        }
    }

    private void updateCachedDate(final long now) {
        if (fastDateFormat != null) {
            final StringBuilder result = fastDateFormat.format(now, new StringBuilder());
            cachedDate = result.toString().toCharArray();
            dateLength = result.length();
        }
    }

    public String formatInstant(final Instant instant) {
        final char[] result = new char[length << 1]; // double size for locales with lengthy DateFormatSymbols
        final int written = formatInstant(instant, result, 0);
        return new String(result, 0, written);
    }

    public int formatInstant(final Instant instant, final char[] buffer, final int startPos) {
        final long epochMillisecond = instant.getEpochMillisecond();
        int result = format(epochMillisecond, buffer, startPos);
        result -= digitsLessThanThree();
        final int pos = formatNanoOfMillisecond(instant.getNanoOfMillisecond(), buffer, startPos + result);
        return writeTimeZone(epochMillisecond, buffer, pos);
    }

    private int digitsLessThanThree() { // in case user specified only 1 or 2 'n' format characters
        return Math.max(0, FixedFormat.MILLI_FRACTION_DIGITS - secondFractionDigits);
    }

    // Profiling showed this method is important to log4j performance. Modify with care!
    // 28 bytes (allows immediate JVM inlining: <= -XX:MaxInlineSize=35 bytes)
    public String format(final long epochMillis) {
        final char[] result = new char[length << 1]; // double size for locales with lengthy DateFormatSymbols
        final int written = format(epochMillis, result, 0);
        return new String(result, 0, written);
    }

    // Profiling showed this method is important to log4j performance. Modify with care!
    // 31 bytes (allows immediate JVM inlining: <= -XX:MaxInlineSize=35 bytes)
    public int format(final long epochMillis, final char[] buffer, final int startPos) {
        // Calculate values by getting the ms values first and do then
        // calculate the hour minute and second values divisions.

        // Get daytime in ms: this does fit into an int
        // int ms = (int) (time % 86400000);
        final int ms = (int) (millisSinceMidnight(epochMillis));
        writeDate(buffer, startPos);
        final int pos = writeTime(ms, buffer, startPos + dateLength);
        return pos - startPos;
    }

    // Profiling showed this method is important to log4j performance. Modify with care!
    // 22 bytes (allows immediate JVM inlining: <= -XX:MaxInlineSize=35 bytes)
    private void writeDate(final char[] buffer, final int startPos) {
        if (cachedDate != null) {
            System.arraycopy(cachedDate, 0, buffer, startPos, dateLength);
        }
    }

    // Profiling showed this method is important to log4j performance. Modify with care!
    // 262 bytes (will be inlined when hot enough: <= -XX:FreqInlineSize=325 bytes on Linux)
    private int writeTime(int ms, final char[] buffer, int pos) {
        final int hourOfDay = ms / 3600000;
        final int hours = hourOfDay + daylightSavingTime(hourOfDay) / 3600000;
        ms -= 3600000 * hourOfDay;

        final int minutes = ms / 60000;
        ms -= 60000 * minutes;

        final int seconds = ms / 1000;
        ms -= 1000 * seconds;

        // Hour
        int temp = hours / 10;
        buffer[pos++] = ((char) (temp + '0'));

        // Do subtract to get remainder instead of doing % 10
        buffer[pos++] = ((char) (hours - 10 * temp + '0'));
        buffer[pos] = timeSeparatorChar;
        pos += timeSeparatorLength;

        // Minute
        temp = minutes / 10;
        buffer[pos++] = ((char) (temp + '0'));

        // Do subtract to get remainder instead of doing % 10
        buffer[pos++] = ((char) (minutes - 10 * temp + '0'));
        buffer[pos] = timeSeparatorChar;
        pos += timeSeparatorLength;

        // Second
        temp = seconds / 10;
        buffer[pos++] = ((char) (temp + '0'));
        buffer[pos++] = ((char) (seconds - 10 * temp + '0'));
        buffer[pos] = millisSeparatorChar;
        pos += millisSeparatorLength;

        // Millisecond
        temp = ms / 100;
        buffer[pos++] = ((char) (temp + '0'));

        ms -= 100 * temp;
        temp = ms / 10;
        buffer[pos++] = ((char) (temp + '0'));

        ms -= 10 * temp;
        buffer[pos++] = ((char) (ms + '0'));
        return pos;
    }

    private int writeTimeZone(final long epochMillis, final char[] buffer, int pos) {
        if (fixedTimeZoneFormat != null) {
            pos = fixedTimeZoneFormat.write(timeZone.getOffset(epochMillis), buffer, pos);
        }
        return pos;
    }

    static int[] TABLE = {
            100000, // 0
            10000, // 1
            1000, // 2
            100, // 3
            10, // 4
            1, // 5
    };

    private int formatNanoOfMillisecond(final int nanoOfMillisecond, final char[] buffer, int pos) {
        int temp;
        int remain = nanoOfMillisecond;
        for (int i = 0; i < secondFractionDigits - FixedFormat.MILLI_FRACTION_DIGITS; i++) {
            final int divisor = TABLE[i];
            temp = remain / divisor;
            buffer[pos++] = ((char) (temp + '0'));
            remain -= divisor * temp; // equivalent of remain % 10
        }
        return pos;
    }

    private int daylightSavingTime(final int hourOfDay) {
        return hourOfDay > 23 ? dstOffsets[23] : dstOffsets[hourOfDay];
    }
}

org/apache/logging/log4j/core/util/datetime/FixedDateFormat.java

 

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