001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.lang;
018
019 /**
020 * <p>Operations on bit-mapped fields.</p>
021 *
022 * @author Apache Software Foundation
023 * @author Apache Jakarta POI
024 * @author Scott Sanders (sanders at apache dot org)
025 * @author Marc Johnson (mjohnson at apache dot org)
026 * @author Andrew C. Oliver (acoliver at apache dot org)
027 * @author Pete Gieser
028 * @author Gary Gregory
029 * @since 2.0
030 * @version $Id: BitField.java 905636 2010-02-02 14:03:32Z niallp $
031 */
032 public class BitField {
033
034 private final int _mask;
035 private final int _shift_count;
036
037 /**
038 * <p>Creates a BitField instance.</p>
039 *
040 * @param mask the mask specifying which bits apply to this
041 * BitField. Bits that are set in this mask are the bits
042 * that this BitField operates on
043 */
044 public BitField(int mask) {
045 _mask = mask;
046 int count = 0;
047 int bit_pattern = mask;
048
049 if (bit_pattern != 0) {
050 while ((bit_pattern & 1) == 0) {
051 count++;
052 bit_pattern >>= 1;
053 }
054 }
055 _shift_count = count;
056 }
057
058 /**
059 * <p>Obtains the value for the specified BitField, appropriately
060 * shifted right.</p>
061 *
062 * <p>Many users of a BitField will want to treat the specified
063 * bits as an int value, and will not want to be aware that the
064 * value is stored as a BitField (and so shifted left so many
065 * bits).</p>
066 *
067 * @see #setValue(int,int)
068 * @param holder the int data containing the bits we're interested
069 * in
070 * @return the selected bits, shifted right appropriately
071 */
072 public int getValue(int holder) {
073 return getRawValue(holder) >> _shift_count;
074 }
075
076 /**
077 * <p>Obtains the value for the specified BitField, appropriately
078 * shifted right, as a short.</p>
079 *
080 * <p>Many users of a BitField will want to treat the specified
081 * bits as an int value, and will not want to be aware that the
082 * value is stored as a BitField (and so shifted left so many
083 * bits).</p>
084 *
085 * @see #setShortValue(short,short)
086 * @param holder the short data containing the bits we're
087 * interested in
088 * @return the selected bits, shifted right appropriately
089 */
090 public short getShortValue(short holder) {
091 return (short) getValue(holder);
092 }
093
094 /**
095 * <p>Obtains the value for the specified BitField, unshifted.</p>
096 *
097 * @param holder the int data containing the bits we're
098 * interested in
099 * @return the selected bits
100 */
101 public int getRawValue(int holder) {
102 return holder & _mask;
103 }
104
105 /**
106 * <p>Obtains the value for the specified BitField, unshifted.</p>
107 *
108 * @param holder the short data containing the bits we're
109 * interested in
110 * @return the selected bits
111 */
112 public short getShortRawValue(short holder) {
113 return (short) getRawValue(holder);
114 }
115
116 /**
117 * <p>Returns whether the field is set or not.</p>
118 *
119 * <p>This is most commonly used for a single-bit field, which is
120 * often used to represent a boolean value; the results of using
121 * it for a multi-bit field is to determine whether *any* of its
122 * bits are set.</p>
123 *
124 * @param holder the int data containing the bits we're interested
125 * in
126 * @return <code>true</code> if any of the bits are set,
127 * else <code>false</code>
128 */
129 public boolean isSet(int holder) {
130 return (holder & _mask) != 0;
131 }
132
133 /**
134 * <p>Returns whether all of the bits are set or not.</p>
135 *
136 * <p>This is a stricter test than {@link #isSet(int)},
137 * in that all of the bits in a multi-bit set must be set
138 * for this method to return <code>true</code>.</p>
139 *
140 * @param holder the int data containing the bits we're
141 * interested in
142 * @return <code>true</code> if all of the bits are set,
143 * else <code>false</code>
144 */
145 public boolean isAllSet(int holder) {
146 return (holder & _mask) == _mask;
147 }
148
149 /**
150 * <p>Replaces the bits with new values.</p>
151 *
152 * @see #getValue(int)
153 * @param holder the int data containing the bits we're
154 * interested in
155 * @param value the new value for the specified bits
156 * @return the value of holder with the bits from the value
157 * parameter replacing the old bits
158 */
159 public int setValue(int holder, int value) {
160 return (holder & ~_mask) | ((value << _shift_count) & _mask);
161 }
162
163 /**
164 * <p>Replaces the bits with new values.</p>
165 *
166 * @see #getShortValue(short)
167 * @param holder the short data containing the bits we're
168 * interested in
169 * @param value the new value for the specified bits
170 * @return the value of holder with the bits from the value
171 * parameter replacing the old bits
172 */
173 public short setShortValue(short holder, short value) {
174 return (short) setValue(holder, value);
175 }
176
177 /**
178 * <p>Clears the bits.</p>
179 *
180 * @param holder the int data containing the bits we're
181 * interested in
182 * @return the value of holder with the specified bits cleared
183 * (set to <code>0</code>)
184 */
185 public int clear(int holder) {
186 return holder & ~_mask;
187 }
188
189 /**
190 * <p>Clears the bits.</p>
191 *
192 * @param holder the short data containing the bits we're
193 * interested in
194 * @return the value of holder with the specified bits cleared
195 * (set to <code>0</code>)
196 */
197 public short clearShort(short holder) {
198 return (short) clear(holder);
199 }
200
201 /**
202 * <p>Clears the bits.</p>
203 *
204 * @param holder the byte data containing the bits we're
205 * interested in
206 *
207 * @return the value of holder with the specified bits cleared
208 * (set to <code>0</code>)
209 */
210 public byte clearByte(byte holder) {
211 return (byte) clear(holder);
212 }
213
214 /**
215 * <p>Sets the bits.</p>
216 *
217 * @param holder the int data containing the bits we're
218 * interested in
219 * @return the value of holder with the specified bits set
220 * to <code>1</code>
221 */
222 public int set(int holder) {
223 return holder | _mask;
224 }
225
226 /**
227 * <p>Sets the bits.</p>
228 *
229 * @param holder the short data containing the bits we're
230 * interested in
231 * @return the value of holder with the specified bits set
232 * to <code>1</code>
233 */
234 public short setShort(short holder) {
235 return (short) set(holder);
236 }
237
238 /**
239 * <p>Sets the bits.</p>
240 *
241 * @param holder the byte data containing the bits we're
242 * interested in
243 *
244 * @return the value of holder with the specified bits set
245 * to <code>1</code>
246 */
247 public byte setByte(byte holder) {
248 return (byte) set(holder);
249 }
250
251 /**
252 * <p>Sets a boolean BitField.</p>
253 *
254 * @param holder the int data containing the bits we're
255 * interested in
256 * @param flag indicating whether to set or clear the bits
257 * @return the value of holder with the specified bits set or
258 * cleared
259 */
260 public int setBoolean(int holder, boolean flag) {
261 return flag ? set(holder) : clear(holder);
262 }
263
264 /**
265 * <p>Sets a boolean BitField.</p>
266 *
267 * @param holder the short data containing the bits we're
268 * interested in
269 * @param flag indicating whether to set or clear the bits
270 * @return the value of holder with the specified bits set or
271 * cleared
272 */
273 public short setShortBoolean(short holder, boolean flag) {
274 return flag ? setShort(holder) : clearShort(holder);
275 }
276
277 /**
278 * <p>Sets a boolean BitField.</p>
279 *
280 * @param holder the byte data containing the bits we're
281 * interested in
282 * @param flag indicating whether to set or clear the bits
283 * @return the value of holder with the specified bits set or
284 * cleared
285 */
286 public byte setByteBoolean(byte holder, boolean flag) {
287 return flag ? setByte(holder) : clearByte(holder);
288 }
289
290 }