| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.impl.store.raw.xact.XactId |
| 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.xact; |
| 22 | |
| 23 | import org.apache.derby.iapi.services.io.FormatIdUtil; |
| 24 | import org.apache.derby.iapi.services.io.StoredFormatIds; |
| 25 | import org.apache.derby.iapi.services.sanity.SanityManager; |
| 26 | |
| 27 | import org.apache.derby.iapi.error.StandardException; |
| 28 | |
| 29 | import org.apache.derby.iapi.store.raw.xact.TransactionId; |
| 30 | |
| 31 | import org.apache.derby.iapi.services.io.CompressedNumber; |
| 32 | |
| 33 | |
| 34 | import java.io.ObjectOutput; |
| 35 | import java.io.ObjectInput; |
| 36 | import java.io.IOException; |
| 37 | |
| 38 | /** |
| 39 | Use this class for a short hand representation of the transaction. This |
| 40 | value is only guarentee to be unique within one continuous operation of the |
| 41 | raw store, in other words, every reboot may reuse the same value. |
| 42 | |
| 43 | Whereas GlobalXactId is unique for all times across all raw store, a XactId |
| 44 | is only unique within a particular rawstore and may be reused. |
| 45 | |
| 46 | XactId keeps track of the outstanding transactionId and is responsible |
| 47 | for dispensing new transactionIds |
| 48 | */ |
| 49 | public class XactId implements TransactionId |
| 50 | { |
| 51 | /* |
| 52 | ** Fields |
| 53 | */ |
| 54 | private long id; // immutable |
| 55 | |
| 56 | /* |
| 57 | ** Constructor |
| 58 | */ |
| 59 | public XactId(long id) { |
| 60 | this.id = id; |
| 61 | } |
| 62 | |
| 63 | /* |
| 64 | * Formatable methods |
| 65 | */ |
| 66 | |
| 67 | // no-arg constructor, required by Formatable |
| 68 | public XactId() { super(); } |
| 69 | |
| 70 | /** |
| 71 | Write this out. |
| 72 | @exception IOException error writing to log stream |
| 73 | */ |
| 74 | public void writeExternal(ObjectOutput out) throws IOException |
| 75 | { |
| 76 | CompressedNumber.writeLong(out, id); |
| 77 | } |
| 78 | |
| 79 | /** |
| 80 | Read this in |
| 81 | @exception IOException error reading from log stream |
| 82 | */ |
| 83 | public void readExternal(ObjectInput in) throws IOException |
| 84 | { |
| 85 | id = CompressedNumber.readLong(in); |
| 86 | } |
| 87 | |
| 88 | /** |
| 89 | Return my format identifier. |
| 90 | */ |
| 91 | public int getTypeFormatId() { |
| 92 | return StoredFormatIds.RAW_STORE_XACT_ID; |
| 93 | } |
| 94 | |
| 95 | /** |
| 96 | TransactionId method |
| 97 | */ |
| 98 | |
| 99 | public int getMaxStoredSize() |
| 100 | { |
| 101 | return FormatIdUtil.getFormatIdByteLength(StoredFormatIds.RAW_STORE_XACT_ID) + |
| 102 | CompressedNumber.MAX_LONG_STORED_SIZE; |
| 103 | } |
| 104 | |
| 105 | public boolean equals(Object other) { |
| 106 | if (other == this) |
| 107 | return true; |
| 108 | |
| 109 | // assume cast will be successful rather than waste time doing an |
| 110 | // instanceof first. Catch the exception if it failed. |
| 111 | try |
| 112 | { |
| 113 | XactId oxid = (XactId)other; |
| 114 | return (id == oxid.id); |
| 115 | } |
| 116 | catch (ClassCastException cce) |
| 117 | { |
| 118 | return false; |
| 119 | } |
| 120 | } |
| 121 | |
| 122 | public int hashCode() |
| 123 | { |
| 124 | return (int)id; |
| 125 | } |
| 126 | |
| 127 | /** |
| 128 | Methods specific to this class |
| 129 | */ |
| 130 | |
| 131 | |
| 132 | /** |
| 133 | Return 0 if a == b, |
| 134 | +ve number if a > b |
| 135 | -ve number if a < b |
| 136 | */ |
| 137 | public static long compare(TransactionId a, TransactionId b) |
| 138 | { |
| 139 | if (a == null || b == null) |
| 140 | { |
| 141 | if (a == null) |
| 142 | return -1; |
| 143 | else if (b == null) |
| 144 | return 1; |
| 145 | else |
| 146 | return 0; |
| 147 | } |
| 148 | |
| 149 | if (SanityManager.DEBUG) |
| 150 | { |
| 151 | SanityManager.ASSERT(a instanceof XactId); |
| 152 | SanityManager.ASSERT(b instanceof XactId); |
| 153 | } |
| 154 | XactId A = (XactId)a; |
| 155 | XactId B = (XactId)b; |
| 156 | |
| 157 | return A.id - B.id; |
| 158 | } |
| 159 | |
| 160 | protected long getId() |
| 161 | { |
| 162 | return id; |
| 163 | } |
| 164 | |
| 165 | |
| 166 | public String toString() |
| 167 | { |
| 168 | // needed for virtual lock table |
| 169 | return Long.toString(id); |
| 170 | } |
| 171 | |
| 172 | |
| 173 | } |
| 174 | |
| 175 | |