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 */ 017package org.apache.commons.lang3; 018 019/** 020 * <p>Supports operations on bit-mapped fields. Instances of this class can be 021 * used to store a flag or data within an {@code int}, {@code short} or 022 * {@code byte}.</p> 023 * 024 * <p>Each {@code BitField} is constructed with a mask value, which indicates 025 * the bits that will be used to store and retrieve the data for that field. 026 * For instance, the mask {@code 0xFF} indicates the least-significant byte 027 * should be used to store the data.</p> 028 * 029 * <p>As an example, consider a car painting machine that accepts 030 * paint instructions as integers. Bit fields can be used to encode this:</p> 031 * 032 *<pre> 033 * // blue, green and red are 1 byte values (0-255) stored in the three least 034 * // significant bytes 035 * BitField blue = new BitField(0xFF); 036 * BitField green = new BitField(0xFF00); 037 * BitField red = new BitField(0xFF0000); 038 * 039 * // anyColor is a flag triggered if any color is used 040 * BitField anyColor = new BitField(0xFFFFFF); 041 * 042 * // isMetallic is a single bit flag 043 * BitField isMetallic = new BitField(0x1000000); 044 *</pre> 045 * 046 * <p>Using these {@code BitField} instances, a paint instruction can be 047 * encoded into an integer:</p> 048 * 049 *<pre> 050 * int paintInstruction = 0; 051 * paintInstruction = red.setValue(paintInstruction, 35); 052 * paintInstruction = green.setValue(paintInstruction, 100); 053 * paintInstruction = blue.setValue(paintInstruction, 255); 054 *</pre> 055 * 056 * <p>Flags and data can be retrieved from the integer:</p> 057 * 058 *<pre> 059 * // Prints true if red, green or blue is non-zero 060 * System.out.println(anyColor.isSet(paintInstruction)); // prints true 061 * 062 * // Prints value of red, green and blue 063 * System.out.println(red.getValue(paintInstruction)); // prints 35 064 * System.out.println(green.getValue(paintInstruction)); // prints 100 065 * System.out.println(blue.getValue(paintInstruction)); // prints 255 066 * 067 * // Prints true if isMetallic was set 068 * System.out.println(isMetallic.isSet(paintInstruction)); // prints false 069 *</pre> 070 * 071 * @since 2.0 072 */ 073public class BitField { 074 075 private final int _mask; 076 private final int _shift_count; 077 078 /** 079 * <p>Creates a BitField instance.</p> 080 * 081 * @param mask the mask specifying which bits apply to this 082 * BitField. Bits that are set in this mask are the bits 083 * that this BitField operates on 084 */ 085 public BitField(final int mask) { 086 _mask = mask; 087 _shift_count = mask == 0 ? 0 : Integer.numberOfTrailingZeros(mask); 088 } 089 090 /** 091 * <p>Obtains the value for the specified BitField, appropriately 092 * shifted right.</p> 093 * 094 * <p>Many users of a BitField will want to treat the specified 095 * bits as an int value, and will not want to be aware that the 096 * value is stored as a BitField (and so shifted left so many 097 * bits).</p> 098 * 099 * @see #setValue(int,int) 100 * @param holder the int data containing the bits we're interested 101 * in 102 * @return the selected bits, shifted right appropriately 103 */ 104 public int getValue(final int holder) { 105 return getRawValue(holder) >> _shift_count; 106 } 107 108 /** 109 * <p>Obtains the value for the specified BitField, appropriately 110 * shifted right, as a short.</p> 111 * 112 * <p>Many users of a BitField will want to treat the specified 113 * bits as an int value, and will not want to be aware that the 114 * value is stored as a BitField (and so shifted left so many 115 * bits).</p> 116 * 117 * @see #setShortValue(short,short) 118 * @param holder the short data containing the bits we're 119 * interested in 120 * @return the selected bits, shifted right appropriately 121 */ 122 public short getShortValue(final short holder) { 123 return (short) getValue(holder); 124 } 125 126 /** 127 * <p>Obtains the value for the specified BitField, unshifted.</p> 128 * 129 * @param holder the int data containing the bits we're 130 * interested in 131 * @return the selected bits 132 */ 133 public int getRawValue(final int holder) { 134 return holder & _mask; 135 } 136 137 /** 138 * <p>Obtains the value for the specified BitField, unshifted.</p> 139 * 140 * @param holder the short data containing the bits we're 141 * interested in 142 * @return the selected bits 143 */ 144 public short getShortRawValue(final short holder) { 145 return (short) getRawValue(holder); 146 } 147 148 /** 149 * <p>Returns whether the field is set or not.</p> 150 * 151 * <p>This is most commonly used for a single-bit field, which is 152 * often used to represent a boolean value; the results of using 153 * it for a multi-bit field is to determine whether *any* of its 154 * bits are set.</p> 155 * 156 * @param holder the int data containing the bits we're interested 157 * in 158 * @return {@code true} if any of the bits are set, 159 * else {@code false} 160 */ 161 public boolean isSet(final int holder) { 162 return (holder & _mask) != 0; 163 } 164 165 /** 166 * <p>Returns whether all of the bits are set or not.</p> 167 * 168 * <p>This is a stricter test than {@link #isSet(int)}, 169 * in that all of the bits in a multi-bit set must be set 170 * for this method to return {@code true}.</p> 171 * 172 * @param holder the int data containing the bits we're 173 * interested in 174 * @return {@code true} if all of the bits are set, 175 * else {@code false} 176 */ 177 public boolean isAllSet(final int holder) { 178 return (holder & _mask) == _mask; 179 } 180 181 /** 182 * <p>Replaces the bits with new values.</p> 183 * 184 * @see #getValue(int) 185 * @param holder the int data containing the bits we're 186 * interested in 187 * @param value the new value for the specified bits 188 * @return the value of holder with the bits from the value 189 * parameter replacing the old bits 190 */ 191 public int setValue(final int holder, final int value) { 192 return (holder & ~_mask) | ((value << _shift_count) & _mask); 193 } 194 195 /** 196 * <p>Replaces the bits with new values.</p> 197 * 198 * @see #getShortValue(short) 199 * @param holder the short data containing the bits we're 200 * interested in 201 * @param value the new value for the specified bits 202 * @return the value of holder with the bits from the value 203 * parameter replacing the old bits 204 */ 205 public short setShortValue(final short holder, final short value) { 206 return (short) setValue(holder, value); 207 } 208 209 /** 210 * <p>Clears the bits.</p> 211 * 212 * @param holder the int data containing the bits we're 213 * interested in 214 * @return the value of holder with the specified bits cleared 215 * (set to {@code 0}) 216 */ 217 public int clear(final int holder) { 218 return holder & ~_mask; 219 } 220 221 /** 222 * <p>Clears the bits.</p> 223 * 224 * @param holder the short data containing the bits we're 225 * interested in 226 * @return the value of holder with the specified bits cleared 227 * (set to {@code 0}) 228 */ 229 public short clearShort(final short holder) { 230 return (short) clear(holder); 231 } 232 233 /** 234 * <p>Clears the bits.</p> 235 * 236 * @param holder the byte data containing the bits we're 237 * interested in 238 * 239 * @return the value of holder with the specified bits cleared 240 * (set to {@code 0}) 241 */ 242 public byte clearByte(final byte holder) { 243 return (byte) clear(holder); 244 } 245 246 /** 247 * <p>Sets the bits.</p> 248 * 249 * @param holder the int data containing the bits we're 250 * interested in 251 * @return the value of holder with the specified bits set 252 * to {@code 1} 253 */ 254 public int set(final int holder) { 255 return holder | _mask; 256 } 257 258 /** 259 * <p>Sets the bits.</p> 260 * 261 * @param holder the short data containing the bits we're 262 * interested in 263 * @return the value of holder with the specified bits set 264 * to {@code 1} 265 */ 266 public short setShort(final short holder) { 267 return (short) set(holder); 268 } 269 270 /** 271 * <p>Sets the bits.</p> 272 * 273 * @param holder the byte data containing the bits we're 274 * interested in 275 * 276 * @return the value of holder with the specified bits set 277 * to {@code 1} 278 */ 279 public byte setByte(final byte holder) { 280 return (byte) set(holder); 281 } 282 283 /** 284 * <p>Sets a boolean BitField.</p> 285 * 286 * @param holder the int data containing the bits we're 287 * interested in 288 * @param flag indicating whether to set or clear the bits 289 * @return the value of holder with the specified bits set or 290 * cleared 291 */ 292 public int setBoolean(final int holder, final boolean flag) { 293 return flag ? set(holder) : clear(holder); 294 } 295 296 /** 297 * <p>Sets a boolean BitField.</p> 298 * 299 * @param holder the short data containing the bits we're 300 * interested in 301 * @param flag indicating whether to set or clear the bits 302 * @return the value of holder with the specified bits set or 303 * cleared 304 */ 305 public short setShortBoolean(final short holder, final boolean flag) { 306 return flag ? setShort(holder) : clearShort(holder); 307 } 308 309 /** 310 * <p>Sets a boolean BitField.</p> 311 * 312 * @param holder the byte data containing the bits we're 313 * interested in 314 * @param flag indicating whether to set or clear the bits 315 * @return the value of holder with the specified bits set or 316 * cleared 317 */ 318 public byte setByteBoolean(final byte holder, final boolean flag) { 319 return flag ? setByte(holder) : clearByte(holder); 320 } 321 322}