| 1 | /* |
| 2 | |
| 3 | Derby - Class com.ihost.cs.JBitSet |
| 4 | |
| 5 | Copyright 1998, 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.iapi.util; |
| 22 | |
| 23 | import org.apache.derby.iapi.services.sanity.SanityManager; |
| 24 | |
| 25 | import java.util.BitSet; |
| 26 | |
| 27 | /** |
| 28 | * JBitSet is a wrapper class for BitSet. It is a fixed length implementation |
| 29 | * which can be extended via the grow() method. It provides additional |
| 30 | * methods to manipulate BitSets. |
| 31 | * NOTE: JBitSet was driven by the (current and perceived) needs of the |
| 32 | * optimizer, but placed in the util package since it is not specific to |
| 33 | * query trees.. |
| 34 | * NOTE: java.util.BitSet is final, so we must provide a wrapper class |
| 35 | * which includes a BitSet member in order to extend the functionality. |
| 36 | * We want to make it look like JBitSet extends BitSet, so we need to |
| 37 | * provide wrapper methods for all of BitSet's methods. |
| 38 | * |
| 39 | * @author Jerry Brenner |
| 40 | */ |
| 41 | public final class JBitSet |
| 42 | { |
| 43 | /* The BitSet that we'd like to extend */ |
| 44 | private final BitSet bitSet; |
| 45 | /* Cache size() of bitSet, since accessed a lot */ |
| 46 | private int size; |
| 47 | |
| 48 | /** |
| 49 | * Construct a JBitSet of the specified size. |
| 50 | * |
| 51 | * @param size The number of bits in the JBitSet. |
| 52 | */ |
| 53 | public JBitSet(int size) |
| 54 | { |
| 55 | bitSet = new BitSet(size); |
| 56 | this.size = size; |
| 57 | } |
| 58 | |
| 59 | /** |
| 60 | * Construct a JBitSet with the specified bitSet. |
| 61 | * |
| 62 | * @param bitSet The BitSet. |
| 63 | * @param size The size of bitSet. |
| 64 | * NOTE: We need to specify the size since the size of a |
| 65 | * BitSet is not guaranteed to be the same as JBitSet.size(). |
| 66 | */ |
| 67 | private JBitSet(BitSet bitSet, int size) |
| 68 | { |
| 69 | this.bitSet = bitSet; |
| 70 | this.size = size; |
| 71 | } |
| 72 | |
| 73 | /** |
| 74 | * Set the BitSet to have the exact same bits set as the parameter's BitSet. |
| 75 | * |
| 76 | * @param sourceBitSet The JBitSet to copy. |
| 77 | */ |
| 78 | public void setTo(JBitSet sourceBitSet) |
| 79 | { |
| 80 | if (SanityManager.DEBUG) |
| 81 | { |
| 82 | SanityManager.ASSERT(size == sourceBitSet.size(), |
| 83 | "JBitSets are expected to be the same size"); |
| 84 | } |
| 85 | /* High reuse solution */ |
| 86 | and(sourceBitSet); |
| 87 | or(sourceBitSet); |
| 88 | } |
| 89 | |
| 90 | /** |
| 91 | * Test to see if one JBitSet contains another one of |
| 92 | * the same size. |
| 93 | * |
| 94 | * @param jBitSet JBitSet that we want to know if it is |
| 95 | * a subset of current JBitSet |
| 96 | * |
| 97 | * @return boolean Whether or not jBitSet is a subset. |
| 98 | */ |
| 99 | public boolean contains(JBitSet jBitSet) |
| 100 | { |
| 101 | if (SanityManager.DEBUG) |
| 102 | { |
| 103 | SanityManager.ASSERT(size == jBitSet.size(), |
| 104 | "JBitSets are expected to be the same size"); |
| 105 | } |
| 106 | for (int bitIndex = 0; bitIndex < size; bitIndex++) |
| 107 | { |
| 108 | if (jBitSet.bitSet.get(bitIndex) && ! (bitSet.get(bitIndex))) |
| 109 | { |
| 110 | return false; |
| 111 | } |
| 112 | } |
| 113 | return true; |
| 114 | } |
| 115 | |
| 116 | /** |
| 117 | * See of a JBitSet has exactly 1 bit set. |
| 118 | * |
| 119 | * @return boolean Whether or not JBitSet has a single bit set. |
| 120 | */ |
| 121 | public boolean hasSingleBitSet() |
| 122 | { |
| 123 | boolean found = false; |
| 124 | |
| 125 | for (int bitIndex = 0; bitIndex < size; bitIndex++) |
| 126 | { |
| 127 | if (bitSet.get(bitIndex)) |
| 128 | { |
| 129 | if (found) |
| 130 | { |
| 131 | return false; |
| 132 | } |
| 133 | else |
| 134 | { |
| 135 | found = true; |
| 136 | } |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | return found; |
| 141 | } |
| 142 | |
| 143 | /** |
| 144 | * Get the first set bit (starting at index 0) from a JBitSet. |
| 145 | * |
| 146 | * @return int Index of first set bit, -1 if none set. |
| 147 | */ |
| 148 | public int getFirstSetBit() |
| 149 | { |
| 150 | for (int bitIndex = 0; bitIndex < size; bitIndex++) |
| 151 | { |
| 152 | if (bitSet.get(bitIndex)) |
| 153 | { |
| 154 | return bitIndex; |
| 155 | } |
| 156 | } |
| 157 | |
| 158 | return -1; |
| 159 | } |
| 160 | |
| 161 | /** |
| 162 | * Grow an existing JBitSet to the specified size. |
| 163 | * |
| 164 | * @param newSize The new size |
| 165 | * |
| 166 | */ |
| 167 | public void grow(int newSize) |
| 168 | { |
| 169 | if (SanityManager.DEBUG) |
| 170 | { |
| 171 | SanityManager.ASSERT(newSize > size, |
| 172 | "New size is expected to be larger than current size"); |
| 173 | } |
| 174 | |
| 175 | size = newSize; |
| 176 | |
| 177 | } |
| 178 | |
| 179 | /** |
| 180 | * Clear all of the bits in this JBitSet |
| 181 | */ |
| 182 | public void clearAll() |
| 183 | { |
| 184 | for (int bitIndex = 0; bitIndex < size; bitIndex++) |
| 185 | { |
| 186 | if (bitSet.get(bitIndex)) |
| 187 | { |
| 188 | bitSet.clear(bitIndex); |
| 189 | } |
| 190 | } |
| 191 | } |
| 192 | |
| 193 | /* Wrapper methods for BitSet's methods */ |
| 194 | public String toString() |
| 195 | { |
| 196 | return bitSet.toString(); |
| 197 | } |
| 198 | |
| 199 | public boolean equals(Object obj) |
| 200 | { |
| 201 | if (SanityManager.DEBUG) |
| 202 | { |
| 203 | SanityManager.ASSERT((obj instanceof JBitSet), |
| 204 | "obj is expected to be a JBitSet " + obj); |
| 205 | } |
| 206 | return bitSet.equals(((JBitSet) obj).bitSet); |
| 207 | } |
| 208 | |
| 209 | public int hashCode() |
| 210 | { |
| 211 | return bitSet.hashCode(); |
| 212 | } |
| 213 | |
| 214 | public Object clone() |
| 215 | { |
| 216 | return new JBitSet((BitSet) bitSet.clone(), size); |
| 217 | } |
| 218 | |
| 219 | public boolean get(int bitIndex) |
| 220 | { |
| 221 | return bitSet.get(bitIndex); |
| 222 | } |
| 223 | |
| 224 | public void set(int bitIndex) |
| 225 | { |
| 226 | bitSet.set(bitIndex); |
| 227 | } |
| 228 | |
| 229 | public void clear(int bitIndex) |
| 230 | { |
| 231 | bitSet.clear(bitIndex); |
| 232 | } |
| 233 | |
| 234 | public void and(JBitSet set) |
| 235 | { |
| 236 | bitSet.and(set.bitSet); |
| 237 | } |
| 238 | |
| 239 | public void or(JBitSet set) |
| 240 | { |
| 241 | bitSet.or(set.bitSet); |
| 242 | } |
| 243 | |
| 244 | public void xor(JBitSet set) |
| 245 | { |
| 246 | bitSet.xor(set.bitSet); |
| 247 | } |
| 248 | |
| 249 | /** |
| 250 | * Return the size of bitSet |
| 251 | * |
| 252 | * @return int Size of bitSet |
| 253 | */ |
| 254 | public int size() |
| 255 | { |
| 256 | return size; |
| 257 | } |
| 258 | } |
| 259 | |