FileHeader


1   /*-
2    * See the file LICENSE for redistribution information.
3    *
4    * Copyright (c) 2002,2006 Oracle.  All rights reserved.
5    *
6    * $Id: FileHeader.java,v 1.37 2006/11/03 03:07:50 mark Exp $
7    */
8   
9   package com.sleepycat.je.log;
10  
11  import java.nio.ByteBuffer  ;
12  import java.sql.Timestamp  ;
13  import java.util.Calendar  ;
14  
15  import com.sleepycat.je.DatabaseException;
16  
17  /**
18   * A FileHeader embodies the header information at the beginning of each log
19   * file.
20   */
21  public class FileHeader implements LoggableObject, LogReadable {
22  
23      /* 
24       * Version 3
25       * ---------
26       * [12328] Add main and dupe tree fanout values for DatabaseImpl.
27       * [12557] Add IN LSN array compression.
28       * [11597] Add a change to FileSummaryLNs: obsolete offset tracking was
29       * added and multiple records are stored for a single file rather than a
30       * single record.  Each record contains the offsets that were tracked since
31       * the last record was written.
32       * [11597] Add the full obsolete LSN in LNLogEntry.
33       *
34       * Version 4
35       * ---------
36       * [#14422] Bump MapLN version from 1 to 2.  Instead of a String for the
37       * comparator class name, store either a serialized string or Comparator.
38       *
39       * Version 5
40       * ---------
41       * [#15195] FileSummaryLN version 3.  Add FileSummary.obsoleteLNSize and
42       * obsoleteLNSizeCounted fields.
43       */
44      private static final int LOG_VERSION = 5;
45  
46      /* 
47       * fileNum is the number of file, starting at 0. An unsigned int, so stored
48       * in a long in memory, but in 4 bytes on disk
49       */
50      private long fileNum; 
51      private long lastEntryInPrevFileOffset;
52      private Timestamp   time;
53      private int logVersion;
54  
55      FileHeader(long fileNum, long lastEntryInPrevFileOffset) {
56          this.fileNum = fileNum;
57          this.lastEntryInPrevFileOffset = lastEntryInPrevFileOffset;
58          Calendar   now = Calendar.getInstance();
59          time = new Timestamp  (now.getTimeInMillis());
60          logVersion = LOG_VERSION;
61      }
62  
63      /** 
64       * For logging only.
65       */
66      public FileHeader() {
67      }
68  
69      public int getLogVersion() {
70          return logVersion;
71      }
72  
73      /**
74       * @return whether the file header has an old version number.
75       *
76       * @throws DatabaseException if the header isn't valid.
77       */
78      boolean validate(String   fileName, long expectedFileNum) 
79          throws DatabaseException {
80  
81          if (fileNum != expectedFileNum) {
82              throw new LogException
83                  ("Wrong filenum in header for file " +
84                   fileName + " expected " +
85                   expectedFileNum + " got " + fileNum);
86          }
87  
88          return logVersion < LOG_VERSION;
89      }
90  
91      /**
92       * @return the offset of the last entry in the previous file.
93       */
94      long getLastEntryInPrevFileOffset() {
95          return lastEntryInPrevFileOffset;
96      }
97  
98      /*
99       * Logging support
100      */
101 
102     /**
103      * @see LoggableObject#getLogType
104      */
105     public LogEntryType getLogType() {
106         return LogEntryType.LOG_FILE_HEADER;
107     }
108 
109     /**
110      * @see LoggableObject#marshallOutsideWriteLatch
111      * Can be marshalled outside the log write latch.
112      */
113     public boolean marshallOutsideWriteLatch() {
114         return true;
115     }
116 
117     /**
118      * @see LoggableObject#countAsObsoleteWhenLogged
119      */
120     public boolean countAsObsoleteWhenLogged() {
121         return false;
122     }
123 
124     /**
125      * @see LoggableObject#postLogWork
126      */
127     public void postLogWork(long justLoggedLsn) 
128         throws DatabaseException {
129     }
130 
131     /**
132      * A header is always a known size.  Is public for unit testing.
133      */
134     public static int entrySize() {
135         return
136             LogUtils.getTimestampLogSize() + // time
137             LogUtils.UNSIGNED_INT_BYTES +    // file number
138             LogUtils.LONG_BYTES +            // lastEntryInPrevFileOffset
139             LogUtils.INT_BYTES;              // logVersion
140     }
141     /**
142      * @see LoggableObject#getLogSize
143      * @return number of bytes used to store this object
144      */
145     public int getLogSize() {
146         return entrySize();
147     }            
148 
149     /**
150      * @see LoggableObject#writeToLog
151      * Serialize this object into the buffer. Update cksum with all
152      * the bytes used by this object
153      * @param logBuffer is the destination buffer
154      */
155     public void writeToLog(ByteBuffer   logBuffer) {
156         LogUtils.writeTimestamp(logBuffer, time);
157         LogUtils.writeUnsignedInt(logBuffer,fileNum);
158         LogUtils.writeLong(logBuffer, lastEntryInPrevFileOffset);
159         LogUtils.writeInt(logBuffer, logVersion);
160     }
161 
162     /**
163      * @see LogReadable#readFromLog
164      * Initialize this object from the data in itemBuf.
165      * @param itemBuf the source buffer
166      */
167     public void readFromLog(ByteBuffer   logBuffer, byte entryTypeVersion)
168     throws LogException {
169         time = LogUtils.readTimestamp(logBuffer);
170         fileNum = LogUtils.getUnsignedInt(logBuffer);
171         lastEntryInPrevFileOffset = LogUtils.readLong(logBuffer);
172         logVersion = LogUtils.readInt(logBuffer);
173         if (logVersion > LOG_VERSION) {
174             throw new LogException("Expected log version " + LOG_VERSION +
175                                    " or earlier but found " + logVersion +
176                                    " -- this version is not supported.");
177         }
178     }
179 
180     /**
181      * @see LogReadable#dumpLog
182      * @param sb destination string buffer
183      * @param verbose if true, dump the full, verbose version
184      */
185     public void dumpLog(StringBuffer   sb, boolean verbose) {
186         sb.append("<FileHeader num=\"0x");
187         sb.append(Long.toHexString(fileNum));
188         sb.append("\" lastEntryInPrevFileOffset=\"0x");
189         sb.append(Long.toHexString(lastEntryInPrevFileOffset));
190         sb.append("\" logVersion=\"0x");
191         sb.append(Integer.toHexString(logVersion));
192         sb.append("\" time=\"").append(time);
193         sb.append("\"/>");
194     }
195 
196     /**
197      * @see LogReadable#logEntryIsTransactional
198      */
199     public boolean logEntryIsTransactional() {
200     return false;
201     }
202 
203     /**
204      * @see LogReadable#getTransactionId
205      */
206     public long getTransactionId() {
207     return 0;
208     }
209 
210     /**
211      * Print in xml format
212      */
213     public String   toString() {
214         StringBuffer   sb = new StringBuffer  ();
215         dumpLog(sb, true);
216         return sb.toString();
217     }
218 }
219
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