/*
    * 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.pattern;
  
  import java.util.concurrent.atomic.AtomicLong;
  
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.config.plugins.Plugin;
  import org.apache.logging.log4j.util.PerformanceSensitive;
  
  /**
   * Formats the event sequence number.
   */
  @Plugin(name = "SequenceNumberPatternConverter", category = "Converter")
  @ConverterKeys({ "sn", "sequenceNumber" })
  @PerformanceSensitive("allocation")
  public final class SequenceNumberPatternConverter extends LogEventPatternConverter {
  
      private static final AtomicLong SEQUENCE = new AtomicLong();
  
      /**
       * Singleton.
       */
      private static final SequenceNumberPatternConverter INSTANCE =
          new SequenceNumberPatternConverter();
  
      /**
       * Private constructor.
       */
      private SequenceNumberPatternConverter() {
          super("Sequence Number", "sn");
      }
  
      /**
       * Obtains an instance of SequencePatternConverter.
       *
       * @param options options, currently ignored, may be null.
       * @return instance of SequencePatternConverter.
       */
      public static SequenceNumberPatternConverter newInstance(final String[] options) {
          return INSTANCE;
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public void format(final LogEvent event, final StringBuilder toAppendTo) {
          toAppendTo.append(SEQUENCE.incrementAndGet());
      }
  }