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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.log4j.pattern;
19  
20  import org.apache.log4j.spi.LoggingEvent;
21  
22  
23  /**
24   * Return the relative time in milliseconds since loading of the LoggingEvent
25   * class.
26   *
27   * @author Ceki Gülcü
28   */
29  public class RelativeTimePatternConverter extends LoggingEventPatternConverter {
30    /**
31     * Cached formatted timestamp.
32     */
33    private CachedTimestamp lastTimestamp = new CachedTimestamp(0, "");
34  
35    /**
36     * Private constructor.
37     */
38    public RelativeTimePatternConverter() {
39      super("Time", "time");
40    }
41  
42    /**
43     * Obtains an instance of RelativeTimePatternConverter.
44     * @param options options, currently ignored, may be null.
45     * @return instance of RelativeTimePatternConverter.
46     */
47    public static RelativeTimePatternConverter newInstance(
48      final String[] options) {
49      return new RelativeTimePatternConverter();
50    }
51  
52    /**
53     * {@inheritDoc}
54     */
55    public void format(final LoggingEvent event, final StringBuffer toAppendTo) {
56      long timestamp = event.timeStamp;
57  
58      if (!lastTimestamp.format(timestamp, toAppendTo)) {
59        final String formatted =
60          Long.toString(timestamp - LoggingEvent.getStartTime());
61        toAppendTo.append(formatted);
62        lastTimestamp = new CachedTimestamp(timestamp, formatted);
63      }
64    }
65  
66    /**
67     * Cached timestamp and formatted value.
68     */
69    private static final class CachedTimestamp {
70      /**
71       * Cached timestamp.
72       */
73      private final long timestamp;
74  
75      /**
76       * Cached formatted timestamp.
77       */
78      private final String formatted;
79  
80      /**
81       * Creates a new instance.
82       * @param timestamp timestamp.
83       * @param formatted formatted timestamp.
84       */
85      public CachedTimestamp(long timestamp, final String formatted) {
86        this.timestamp = timestamp;
87        this.formatted = formatted;
88      }
89  
90      /**
91       * Appends the cached formatted timestamp to the buffer if timestamps match.
92       * @param newTimestamp requested timestamp.
93       * @param toAppendTo buffer to append formatted timestamp.
94       * @return true if requested timestamp matched cached timestamp.
95       */
96      public boolean format(long newTimestamp, final StringBuffer toAppendTo) {
97        if (newTimestamp == timestamp) {
98          toAppendTo.append(formatted);
99  
100         return true;
101       }
102 
103       return false;
104     }
105   }
106 }