Source code
Description: source: package: org.apache.commons.lang3, class: BitField

    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 * 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}.
    023 *
    024 * <p>Each {@link 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 {@link 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 shiftCount;
    077
    078    /**
    079     * Creates a BitField instance.
    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        this.mask = mask;
    087        this.shiftCount = mask == 0 ? 0 : Integer.numberOfTrailingZeros(mask);
    088    }
    089
    090    /**
    091     * Clears the bits.
    092     *
    093     * @param holder the int data containing the bits we're
    094     *  interested in
    095     * @return the value of holder with the specified bits cleared
    096     *  (set to {@code 0})
    097     */
    098    public int clear(final int holder) {
    099        return holder & ~mask;
    100    }
    101
    102    /**
    103     * Clears the bits.
    104     *
    105     * @param holder the byte data containing the bits we're
    106     *  interested in
    107     *
    108     * @return the value of holder with the specified bits cleared
    109     *  (set to {@code 0})
    110     */
    111    public byte clearByte(final byte holder) {
    112        return (byte) clear(holder);
    113    }
    114
    115    /**
    116     * Clears the bits.
    117     *
    118     * @param holder the short data containing the bits we're
    119     *  interested in
    120     * @return the value of holder with the specified bits cleared
    121     *  (set to {@code 0})
    122     */
    123    public short clearShort(final short holder) {
    124        return (short) clear(holder);
    125    }
    126
    127    /**
    128     * Obtains the value for the specified BitField, unshifted.
    129     *
    130     * @param holder the int data containing the bits we're
    131     *  interested in
    132     * @return the selected bits
    133     */
    134    public int getRawValue(final int holder) {
    135        return holder & mask;
    136    }
    137
    138    /**
    139     * Obtains the value for the specified BitField, unshifted.
    140     *
    141     * @param holder the short data containing the bits we're
    142     *  interested in
    143     * @return the selected bits
    144     */
    145    public short getShortRawValue(final short holder) {
    146        return (short) getRawValue(holder);
    147    }
    148
    149    /**
    150     * Obtains the value for the specified BitField, appropriately
    151     * shifted right, as a short.
    152     *
    153     * <p>Many users of a BitField will want to treat the specified
    154     * bits as an int value, and will not want to be aware that the
    155     * value is stored as a BitField (and so shifted left so many
    156     * bits).</p>
    157     *
    158     * @see #setShortValue(short,short)
    159     * @param holder the short data containing the bits we're
    160     *  interested in
    161     * @return the selected bits, shifted right appropriately
    162     */
    163    public short getShortValue(final short holder) {
    164        return (short) getValue(holder);
    165    }
    166
    167    /**
    168     * Obtains the value for the specified BitField, appropriately
    169     * shifted right.
    170     *
    171     * <p>Many users of a BitField will want to treat the specified
    172     * bits as an int value, and will not want to be aware that the
    173     * value is stored as a BitField (and so shifted left so many
    174     * bits).</p>
    175     *
    176     * @see #setValue(int,int)
    177     * @param holder the int data containing the bits we're interested
    178     *  in
    179     * @return the selected bits, shifted right appropriately
    180     */
    181    public int getValue(final int holder) {
    182        return getRawValue(holder) >> shiftCount;
    183    }
    184
    185    /**
    186     * Returns whether all of the bits are set or not.
    187     *
    188     * <p>This is a stricter test than {@link #isSet(int)},
    189     * in that all of the bits in a multi-bit set must be set
    190     * for this method to return {@code true}.</p>
    191     *
    192     * @param holder the int data containing the bits we're
    193     *  interested in
    194     * @return {@code true} if all of the bits are set,
    195     *  else {@code false}
    196     */
    197    public boolean isAllSet(final int holder) {
    198        return (holder & mask) == mask;
    199    }
    200
    201    /**
    202     * Returns whether the field is set or not.
    203     *
    204     * <p>This is most commonly used for a single-bit field, which is
    205     * often used to represent a boolean value; the results of using
    206     * it for a multi-bit field is to determine whether *any* of its
    207     * bits are set.</p>
    208     *
    209     * @param holder the int data containing the bits we're interested
    210     *  in
    211     * @return {@code true} if any of the bits are set,
    212     *  else {@code false}
    213     */
    214    public boolean isSet(final int holder) {
    215        return (holder & mask) != 0;
    216    }
    217
    218    /**
    219     * Sets the bits.
    220     *
    221     * @param holder the int data containing the bits we're
    222     *  interested in
    223     * @return the value of holder with the specified bits set
    224     *  to {@code 1}
    225     */
    226    public int set(final int holder) {
    227        return holder | mask;
    228    }
    229
    230    /**
    231     * Sets a boolean BitField.
    232     *
    233     * @param holder the int data containing the bits we're
    234     *  interested in
    235     * @param flag indicating whether to set or clear the bits
    236     * @return the value of holder with the specified bits set or
    237     *         cleared
    238     */
    239    public int setBoolean(final int holder, final boolean flag) {
    240        return flag ? set(holder) : clear(holder);
    241    }
    242
    243    /**
    244     * Sets the bits.
    245     *
    246     * @param holder the byte data containing the bits we're
    247     *  interested in
    248     *
    249     * @return the value of holder with the specified bits set
    250     *  to {@code 1}
    251     */
    252    public byte setByte(final byte holder) {
    253        return (byte) set(holder);
    254    }
    255
    256    /**
    257     * Sets a boolean BitField.
    258     *
    259     * @param holder the byte data containing the bits we're
    260     *  interested in
    261     * @param flag indicating whether to set or clear the bits
    262     * @return the value of holder with the specified bits set or
    263     *  cleared
    264     */
    265    public byte setByteBoolean(final byte holder, final boolean flag) {
    266        return flag ? setByte(holder) : clearByte(holder);
    267    }
    268
    269    /**
    270     * Sets the bits.
    271     *
    272     * @param holder the short data containing the bits we're
    273     *  interested in
    274     * @return the value of holder with the specified bits set
    275     *  to {@code 1}
    276     */
    277    public short setShort(final short holder) {
    278        return (short) set(holder);
    279    }
    280
    281    /**
    282     * Sets a boolean BitField.
    283     *
    284     * @param holder the short data containing the bits we're
    285     *  interested in
    286     * @param flag indicating whether to set or clear the bits
    287     * @return the value of holder with the specified bits set or
    288     *  cleared
    289     */
    290    public short setShortBoolean(final short holder, final boolean flag) {
    291        return flag ? setShort(holder) : clearShort(holder);
    292    }
    293
    294    /**
    295     * Replaces the bits with new values.
    296     *
    297     * @see #getShortValue(short)
    298     * @param holder the short data containing the bits we're
    299     *  interested in
    300     * @param value the new value for the specified bits
    301     * @return the value of holder with the bits from the value
    302     *  parameter replacing the old bits
    303     */
    304    public short setShortValue(final short holder, final short value) {
    305        return (short) setValue(holder, value);
    306    }
    307
    308    /**
    309     * Replaces the bits with new values.
    310     *
    311     * @see #getValue(int)
    312     * @param holder the int data containing the bits we're
    313     *  interested in
    314     * @param value the new value for the specified bits
    315     * @return the value of holder with the bits from the value
    316     *  parameter replacing the old bits
    317     */
    318    public int setValue(final int holder, final int value) {
    319        return holder & ~mask | value << shiftCount & mask;
    320    }
    321
    322}