| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.impl.store.raw.log.LogCounter |
| 4 | |
| 5 | Copyright 1997, 2004 The Apache Software Foundation or its licensors, as applicable. |
| 6 | |
| 7 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 8 | you may not use this file except in compliance with the License. |
| 9 | You may obtain a copy of the License at |
| 10 | |
| 11 | http://www.apache.org/licenses/LICENSE-2.0 |
| 12 | |
| 13 | Unless required by applicable law or agreed to in writing, software |
| 14 | distributed under the License is distributed on an "AS IS" BASIS, |
| 15 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 16 | See the License for the specific language governing permissions and |
| 17 | limitations under the License. |
| 18 | |
| 19 | */ |
| 20 | |
| 21 | package org.apache.derby.impl.store.raw.log; |
| 22 | |
| 23 | import org.apache.derby.iapi.services.sanity.SanityManager; |
| 24 | import org.apache.derby.iapi.services.io.FormatIdUtil; |
| 25 | import org.apache.derby.iapi.services.io.StoredFormatIds; |
| 26 | import org.apache.derby.iapi.store.raw.log.LogInstant; |
| 27 | import org.apache.derby.iapi.store.access.DatabaseInstant; |
| 28 | import org.apache.derby.iapi.services.io.CompressedNumber; |
| 29 | |
| 30 | import java.io.IOException; |
| 31 | import java.io.ObjectInput; |
| 32 | import java.io.ObjectOutput; |
| 33 | |
| 34 | /** |
| 35 | A very simple log instant implementation. |
| 36 | |
| 37 | Within the stored log record a log counter is represented as a long, |
| 38 | hence the getValueAsLong() method. Outside the LogFactory the instant |
| 39 | is passed around as a LogCounter (through its LogInstant interface). |
| 40 | |
| 41 | The way the long is encoded is such that < == > correctly tells if |
| 42 | one log instant is lessThan, equals or greater than another. |
| 43 | |
| 44 | */ |
| 45 | public class LogCounter implements LogInstant { |
| 46 | |
| 47 | /******************************************************** |
| 48 | ** |
| 49 | ** This class implements Formatable. That means that it |
| 50 | ** can write itself to and from a formatted stream. If |
| 51 | ** you add more fields to this class, make sure that you |
| 52 | ** also write/read them with the writeExternal()/readExternal() |
| 53 | ** methods. |
| 54 | ** |
| 55 | ** If, between releases, you add more fields to this class, |
| 56 | ** then you should bump the version number emitted by the getTypeFormatId() |
| 57 | ** method. |
| 58 | ** |
| 59 | ********************************************************/ |
| 60 | |
| 61 | /** A well defined value of an invalid log instant. */ |
| 62 | public static final long INVALID_LOG_INSTANT = 0; |
| 63 | |
| 64 | // max possible log file number in versions before 10.1 is 2^22 -1 |
| 65 | public static final long DERBY_10_0_MAX_LOGFILE_NUMBER = (long)0x003FFFFFL; // 4194303 |
| 66 | // max possible log file number is 2^31 -1 |
| 67 | public static final long MAX_LOGFILE_NUMBER = (long)0x7FFFFFFFL; // 2147483647 |
| 68 | // lower end of 32 bits in long type are used to store the log file position |
| 69 | private static final long FILE_NUMBER_SHIFT = 32; |
| 70 | |
| 71 | // reserve top 4 bits in log file size for future use |
| 72 | public static final long MAX_LOGFILE_SIZE = (long)0x0FFFFFFFL; // 268435455 |
| 73 | // 32 bits are used to store the log file postion |
| 74 | private static final long FILE_POSITION_MASK = (long)0x7FFFFFFFL; |
| 75 | |
| 76 | private long fileNumber; |
| 77 | private long filePosition; |
| 78 | |
| 79 | // contructors |
| 80 | public LogCounter(long value) { |
| 81 | fileNumber = getLogFileNumber(value); |
| 82 | filePosition = getLogFilePosition(value); |
| 83 | } |
| 84 | |
| 85 | public LogCounter(long fileNumber, long position) { |
| 86 | |
| 87 | if (SanityManager.DEBUG) { |
| 88 | SanityManager.ASSERT(fileNumber > 0, "illegal fileNumber"); |
| 89 | SanityManager.ASSERT(position > 0, "illegal file position"); |
| 90 | |
| 91 | SanityManager.ASSERT(position < MAX_LOGFILE_SIZE, |
| 92 | "log file position exceeded max log file size"); |
| 93 | SanityManager.ASSERT(fileNumber < MAX_LOGFILE_NUMBER, |
| 94 | "log file number exceeded max log file number"); |
| 95 | } |
| 96 | |
| 97 | this.fileNumber = fileNumber; |
| 98 | this.filePosition = position; |
| 99 | } |
| 100 | |
| 101 | /** |
| 102 | * Public niladic constructor needed for Formatable interface. |
| 103 | */ |
| 104 | public LogCounter() {} |
| 105 | |
| 106 | /** |
| 107 | Static functions that can only be used inside the RawStore's log |
| 108 | factory which passes the log counter around encoded as a long |
| 109 | */ |
| 110 | |
| 111 | // make a log instant from 2 longs and return a long which is the long |
| 112 | // representatin of a LogCounter |
| 113 | static public final long makeLogInstantAsLong(long filenum, long filepos) |
| 114 | { |
| 115 | if (SanityManager.DEBUG) { |
| 116 | SanityManager.ASSERT(filenum > 0, "illegal fileNumber"); |
| 117 | SanityManager.ASSERT(filepos > 0, "illegal file position"); |
| 118 | |
| 119 | SanityManager.ASSERT(filepos < MAX_LOGFILE_SIZE, |
| 120 | "log file position exceeded max log file size"); |
| 121 | SanityManager.ASSERT(filenum < MAX_LOGFILE_NUMBER, |
| 122 | "log file number exceeded max log file number"); |
| 123 | } |
| 124 | |
| 125 | return ((filenum << FILE_NUMBER_SHIFT) | filepos); |
| 126 | } |
| 127 | |
| 128 | |
| 129 | static public final long getLogFilePosition(long valueAsLong) |
| 130 | { |
| 131 | return valueAsLong & FILE_POSITION_MASK; |
| 132 | } |
| 133 | |
| 134 | static public final long getLogFileNumber(long valueAsLong) |
| 135 | { |
| 136 | return valueAsLong >>> FILE_NUMBER_SHIFT; |
| 137 | } |
| 138 | |
| 139 | /** LogScan methods */ |
| 140 | |
| 141 | public boolean lessThan(DatabaseInstant other) { |
| 142 | LogCounter compare = (LogCounter)other; |
| 143 | |
| 144 | return (fileNumber == compare.fileNumber) ? |
| 145 | filePosition < compare.filePosition : |
| 146 | fileNumber < compare.fileNumber; |
| 147 | } |
| 148 | |
| 149 | public boolean equals(Object other) { |
| 150 | if (this == other) |
| 151 | return true; |
| 152 | |
| 153 | if (!(other instanceof LogCounter)) |
| 154 | return false; |
| 155 | |
| 156 | LogCounter compare = (LogCounter)other; |
| 157 | |
| 158 | return fileNumber == compare.fileNumber && |
| 159 | filePosition == compare.filePosition; |
| 160 | } |
| 161 | |
| 162 | public DatabaseInstant next() { |
| 163 | return new LogCounter( makeLogInstantAsLong(fileNumber, filePosition) + 1); |
| 164 | } |
| 165 | |
| 166 | public DatabaseInstant prior() { |
| 167 | return new LogCounter( makeLogInstantAsLong(fileNumber, filePosition) - 1); |
| 168 | } |
| 169 | |
| 170 | public int hashCode() { |
| 171 | return (int) (filePosition ^ fileNumber); |
| 172 | } |
| 173 | |
| 174 | public String toString() { |
| 175 | return "(" + fileNumber + "," + filePosition + ")"; |
| 176 | } |
| 177 | |
| 178 | public static String toDebugString(long instant) |
| 179 | { |
| 180 | if (SanityManager.DEBUG) |
| 181 | return "(" + getLogFileNumber(instant) + "," + getLogFilePosition(instant) + ")"; |
| 182 | else |
| 183 | return null; |
| 184 | } |
| 185 | |
| 186 | /** |
| 187 | These following methods are only intended to be called by an |
| 188 | implementation of a log factory. All other uses of this object should |
| 189 | only see it as a log instant. |
| 190 | */ |
| 191 | public long getValueAsLong() { |
| 192 | return makeLogInstantAsLong(fileNumber, filePosition); |
| 193 | } |
| 194 | |
| 195 | public long getLogFilePosition() |
| 196 | { |
| 197 | return filePosition; |
| 198 | } |
| 199 | |
| 200 | public long getLogFileNumber() |
| 201 | { |
| 202 | return fileNumber; |
| 203 | } |
| 204 | |
| 205 | |
| 206 | /* |
| 207 | * methods for the Formatable interface |
| 208 | */ |
| 209 | |
| 210 | /** |
| 211 | * Read this in. |
| 212 | * @exception IOException error reading from log stream |
| 213 | * @exception ClassNotFoundException corrupted log stream |
| 214 | */ |
| 215 | public void readExternal(ObjectInput oi) throws IOException, ClassNotFoundException { |
| 216 | fileNumber = CompressedNumber.readLong(oi); |
| 217 | filePosition = CompressedNumber.readLong(oi); |
| 218 | } |
| 219 | |
| 220 | /** |
| 221 | * Write this out. |
| 222 | * @exception IOException error writing to log stream |
| 223 | */ |
| 224 | public void writeExternal(ObjectOutput oo) throws IOException { |
| 225 | CompressedNumber.writeLong(oo,fileNumber); |
| 226 | CompressedNumber.writeLong(oo,filePosition); |
| 227 | } |
| 228 | |
| 229 | /** |
| 230 | * Get the formatID which corresponds to this class. |
| 231 | * |
| 232 | * @return the formatID of this class |
| 233 | */ |
| 234 | public int getTypeFormatId() { return StoredFormatIds.LOG_COUNTER; } |
| 235 | |
| 236 | } |