| 1 | /* |
| 2 | * Copyright 2001-2005 Stephen Colebourne |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | package org.joda.time.tz; |
| 17 | |
| 18 | import org.joda.time.DateTimeZone; |
| 19 | |
| 20 | /** |
| 21 | * Improves the performance of requesting time zone offsets and name keys by |
| 22 | * caching the results. Time zones that have simple rules or are fixed should |
| 23 | * not be cached, as it is unlikely to improve performance. |
| 24 | * <p> |
| 25 | * CachedDateTimeZone is thread-safe and immutable. |
| 26 | * |
| 27 | * @author Brian S O'Neill |
| 28 | * @since 1.0 |
| 29 | */ |
| 30 | public class CachedDateTimeZone extends DateTimeZone { |
| 31 | |
| 32 | private static final long serialVersionUID = 5472298452022250685L; |
| 33 | |
| 34 | private static final int cInfoCacheMask; |
| 35 | |
| 36 | static { |
| 37 | Integer i; |
| 38 | try { |
| 39 | i = Integer.getInteger("org.joda.time.tz.CachedDateTimeZone.size"); |
| 40 | } catch (SecurityException e) { |
| 41 | i = null; |
| 42 | } |
| 43 | |
| 44 | int cacheSize; |
| 45 | if (i == null) { |
| 46 | // With a cache size of 512, dates that lie within any 69.7 year |
| 47 | // period have no cache collisions. |
| 48 | cacheSize = 512; // (1 << 9) |
| 49 | } else { |
| 50 | cacheSize = i.intValue(); |
| 51 | // Ensure cache size is even power of 2. |
| 52 | cacheSize--; |
| 53 | int shift = 0; |
| 54 | while (cacheSize > 0) { |
| 55 | shift++; |
| 56 | cacheSize >>= 1; |
| 57 | } |
| 58 | cacheSize = 1 << shift; |
| 59 | } |
| 60 | |
| 61 | cInfoCacheMask = cacheSize - 1; |
| 62 | } |
| 63 | |
| 64 | /** |
| 65 | * Returns a new CachedDateTimeZone unless given zone is already cached. |
| 66 | */ |
| 67 | public static CachedDateTimeZone forZone(DateTimeZone zone) { |
| 68 | if (zone instanceof CachedDateTimeZone) { |
| 69 | return (CachedDateTimeZone)zone; |
| 70 | } |
| 71 | return new CachedDateTimeZone(zone); |
| 72 | } |
| 73 | |
| 74 | /* |
| 75 | * Caching is performed by breaking timeline down into periods of 2^32 |
| 76 | * milliseconds, or about 49.7 days. A year has about 7.3 periods, usually |
| 77 | * with only 2 time zone offset periods. Most of the 49.7 day periods will |
| 78 | * have no transition, about one quarter have one transition, and very rare |
| 79 | * cases have multiple transitions. |
| 80 | */ |
| 81 | |
| 82 | private final DateTimeZone iZone; |
| 83 | |
| 84 | private transient Info[] iInfoCache; |
| 85 | |
| 86 | private CachedDateTimeZone(DateTimeZone zone) { |
| 87 | super(zone.getID()); |
| 88 | iZone = zone; |
| 89 | iInfoCache = new Info[cInfoCacheMask + 1]; |
| 90 | } |
| 91 | |
| 92 | private void readObject(java.io.ObjectInputStream in) |
| 93 | throws java.io.IOException, ClassNotFoundException |
| 94 | { |
| 95 | in.defaultReadObject(); |
| 96 | iInfoCache = new Info[cInfoCacheMask + 1]; |
| 97 | } |
| 98 | |
| 99 | /** |
| 100 | * Returns the DateTimeZone being wrapped. |
| 101 | */ |
| 102 | public DateTimeZone getUncachedZone() { |
| 103 | return iZone; |
| 104 | } |
| 105 | |
| 106 | public String getNameKey(long instant) { |
| 107 | return getInfo(instant).getNameKey(instant); |
| 108 | } |
| 109 | |
| 110 | public int getOffset(long instant) { |
| 111 | return getInfo(instant).getOffset(instant); |
| 112 | } |
| 113 | |
| 114 | public int getStandardOffset(long instant) { |
| 115 | return getInfo(instant).getStandardOffset(instant); |
| 116 | } |
| 117 | |
| 118 | public boolean isFixed() { |
| 119 | return iZone.isFixed(); |
| 120 | } |
| 121 | |
| 122 | public long nextTransition(long instant) { |
| 123 | return iZone.nextTransition(instant); |
| 124 | } |
| 125 | |
| 126 | public long previousTransition(long instant) { |
| 127 | return iZone.previousTransition(instant); |
| 128 | } |
| 129 | |
| 130 | public int hashCode() { |
| 131 | return iZone.hashCode(); |
| 132 | } |
| 133 | |
| 134 | public boolean equals(Object obj) { |
| 135 | if (this == obj) { |
| 136 | return true; |
| 137 | } |
| 138 | if (obj instanceof CachedDateTimeZone) { |
| 139 | return iZone.equals(((CachedDateTimeZone)obj).iZone); |
| 140 | } |
| 141 | return false; |
| 142 | } |
| 143 | |
| 144 | // Although accessed by multiple threads, this method doesn't need to be |
| 145 | // synchronized. |
| 146 | |
| 147 | private Info getInfo(long millis) { |
| 148 | int period = (int)(millis >> 32); |
| 149 | Info[] cache = iInfoCache; |
| 150 | int index = period & cInfoCacheMask; |
| 151 | Info info = cache[index]; |
| 152 | if (info == null || (int)((info.iPeriodStart >> 32)) != period) { |
| 153 | info = createInfo(millis); |
| 154 | cache[index] = info; |
| 155 | } |
| 156 | return info; |
| 157 | } |
| 158 | |
| 159 | private Info createInfo(long millis) { |
| 160 | long periodStart = millis & (0xffffffffL << 32); |
| 161 | Info info = new Info(iZone, periodStart); |
| 162 | |
| 163 | long end = periodStart | 0xffffffffL; |
| 164 | Info chain = info; |
| 165 | while (true) { |
| 166 | long next = iZone.nextTransition(periodStart); |
| 167 | if (next == periodStart || next > end) { |
| 168 | break; |
| 169 | } |
| 170 | periodStart = next; |
| 171 | chain = (chain.iNextInfo = new Info(iZone, periodStart)); |
| 172 | } |
| 173 | |
| 174 | return info; |
| 175 | } |
| 176 | |
| 177 | private final static class Info { |
| 178 | // For first Info in chain, iPeriodStart's lower 32 bits are clear. |
| 179 | public final long iPeriodStart; |
| 180 | public final DateTimeZone iZoneRef; |
| 181 | |
| 182 | Info iNextInfo; |
| 183 | |
| 184 | private String iNameKey; |
| 185 | private int iOffset = Integer.MIN_VALUE; |
| 186 | private int iStandardOffset = Integer.MIN_VALUE; |
| 187 | |
| 188 | Info(DateTimeZone zone, long periodStart) { |
| 189 | iPeriodStart = periodStart; |
| 190 | iZoneRef = zone; |
| 191 | } |
| 192 | |
| 193 | public String getNameKey(long millis) { |
| 194 | if (iNextInfo == null || millis < iNextInfo.iPeriodStart) { |
| 195 | if (iNameKey == null) { |
| 196 | iNameKey = iZoneRef.getNameKey(iPeriodStart); |
| 197 | } |
| 198 | return iNameKey; |
| 199 | } |
| 200 | return iNextInfo.getNameKey(millis); |
| 201 | } |
| 202 | |
| 203 | public int getOffset(long millis) { |
| 204 | if (iNextInfo == null || millis < iNextInfo.iPeriodStart) { |
| 205 | if (iOffset == Integer.MIN_VALUE) { |
| 206 | iOffset = iZoneRef.getOffset(iPeriodStart); |
| 207 | } |
| 208 | return iOffset; |
| 209 | } |
| 210 | return iNextInfo.getOffset(millis); |
| 211 | } |
| 212 | |
| 213 | public int getStandardOffset(long millis) { |
| 214 | if (iNextInfo == null || millis < iNextInfo.iPeriodStart) { |
| 215 | if (iStandardOffset == Integer.MIN_VALUE) { |
| 216 | iStandardOffset = iZoneRef.getStandardOffset(iPeriodStart); |
| 217 | } |
| 218 | return iStandardOffset; |
| 219 | } |
| 220 | return iNextInfo.getStandardOffset(millis); |
| 221 | } |
| 222 | } |
| 223 | } |