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Java example source code file (BitField.java)

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bitfield

The BitField.java Java example source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3;

/**
 * <p>Supports operations on bit-mapped fields. Instances of this class can be 
 * used to store a flag or data within an {@code int}, {@code short} or 
 * {@code byte}.</p>
 * 
 * <p>Each {@code BitField} is constructed with a mask value, which indicates
 * the bits that will be used to store and retrieve the data for that field. 
 * For instance, the mask {@code 0xFF} indicates the least-significant byte 
 * should be used to store the data.</p>
 * 
 * <p>As an example, consider a car painting machine that accepts
 * paint instructions as integers. Bit fields can be used to encode this:</p>
 *
 *<pre>
 *    // blue, green and red are 1 byte values (0-255) stored in the three least 
 *    // significant bytes
 *    BitField blue = new BitField(0xFF);
 *    BitField green = new BitField(0xFF00);
 *    BitField red = new BitField(0xFF0000);
 * 
 *    // anyColor is a flag triggered if any color is used
 *    BitField anyColor = new BitField(0xFFFFFF);
 * 
 *    // isMetallic is a single bit flag
 *    BitField isMetallic = new BitField(0x1000000);
 *</pre>
 *
 * <p>Using these {@code BitField} instances, a paint instruction can be
 * encoded into an integer:</p>
 *
 *<pre>
 *    int paintInstruction = 0;
 *    paintInstruction = red.setValue(paintInstruction, 35);
 *    paintInstruction = green.setValue(paintInstruction, 100);
 *    paintInstruction = blue.setValue(paintInstruction, 255);
 *</pre>
 *
 * <p>Flags and data can be retrieved from the integer:

* *<pre> * // Prints true if red, green or blue is non-zero * System.out.println(anyColor.isSet(paintInstruction)); // prints true * * // Prints value of red, green and blue * System.out.println(red.getValue(paintInstruction)); // prints 35 * System.out.println(green.getValue(paintInstruction)); // prints 100 * System.out.println(blue.getValue(paintInstruction)); // prints 255 * * // Prints true if isMetallic was set * System.out.println(isMetallic.isSet(paintInstruction)); // prints false *</pre> * * @since 2.0 */ public class BitField { private final int _mask; private final int _shift_count; /** * <p>Creates a BitField instance.

* * @param mask the mask specifying which bits apply to this * BitField. Bits that are set in this mask are the bits * that this BitField operates on */ public BitField(final int mask) { _mask = mask; _shift_count = mask != 0 ? Integer.numberOfTrailingZeros(mask) : 0; } /** * <p>Obtains the value for the specified BitField, appropriately * shifted right.</p> * * <p>Many users of a BitField will want to treat the specified * bits as an int value, and will not want to be aware that the * value is stored as a BitField (and so shifted left so many * bits).</p> * * @see #setValue(int,int) * @param holder the int data containing the bits we're interested * in * @return the selected bits, shifted right appropriately */ public int getValue(final int holder) { return getRawValue(holder) >> _shift_count; } /** * <p>Obtains the value for the specified BitField, appropriately * shifted right, as a short.</p> * * <p>Many users of a BitField will want to treat the specified * bits as an int value, and will not want to be aware that the * value is stored as a BitField (and so shifted left so many * bits).</p> * * @see #setShortValue(short,short) * @param holder the short data containing the bits we're * interested in * @return the selected bits, shifted right appropriately */ public short getShortValue(final short holder) { return (short) getValue(holder); } /** * <p>Obtains the value for the specified BitField, unshifted.

* * @param holder the int data containing the bits we're * interested in * @return the selected bits */ public int getRawValue(final int holder) { return holder & _mask; } /** * <p>Obtains the value for the specified BitField, unshifted.

* * @param holder the short data containing the bits we're * interested in * @return the selected bits */ public short getShortRawValue(final short holder) { return (short) getRawValue(holder); } /** * <p>Returns whether the field is set or not.

* * <p>This is most commonly used for a single-bit field, which is * often used to represent a boolean value; the results of using * it for a multi-bit field is to determine whether *any* of its * bits are set.</p> * * @param holder the int data containing the bits we're interested * in * @return {@code true} if any of the bits are set, * else {@code false} */ public boolean isSet(final int holder) { return (holder & _mask) != 0; } /** * <p>Returns whether all of the bits are set or not.

* * <p>This is a stricter test than {@link #isSet(int)}, * in that all of the bits in a multi-bit set must be set * for this method to return {@code true}.</p> * * @param holder the int data containing the bits we're * interested in * @return {@code true} if all of the bits are set, * else {@code false} */ public boolean isAllSet(final int holder) { return (holder & _mask) == _mask; } /** * <p>Replaces the bits with new values.

* * @see #getValue(int) * @param holder the int data containing the bits we're * interested in * @param value the new value for the specified bits * @return the value of holder with the bits from the value * parameter replacing the old bits */ public int setValue(final int holder, final int value) { return (holder & ~_mask) | ((value << _shift_count) & _mask); } /** * <p>Replaces the bits with new values.

* * @see #getShortValue(short) * @param holder the short data containing the bits we're * interested in * @param value the new value for the specified bits * @return the value of holder with the bits from the value * parameter replacing the old bits */ public short setShortValue(final short holder, final short value) { return (short) setValue(holder, value); } /** * <p>Clears the bits.

* * @param holder the int data containing the bits we're * interested in * @return the value of holder with the specified bits cleared * (set to {@code 0}) */ public int clear(final int holder) { return holder & ~_mask; } /** * <p>Clears the bits.

* * @param holder the short data containing the bits we're * interested in * @return the value of holder with the specified bits cleared * (set to {@code 0}) */ public short clearShort(final short holder) { return (short) clear(holder); } /** * <p>Clears the bits.

* * @param holder the byte data containing the bits we're * interested in * * @return the value of holder with the specified bits cleared * (set to {@code 0}) */ public byte clearByte(final byte holder) { return (byte) clear(holder); } /** * <p>Sets the bits.

* * @param holder the int data containing the bits we're * interested in * @return the value of holder with the specified bits set * to {@code 1} */ public int set(final int holder) { return holder | _mask; } /** * <p>Sets the bits.

* * @param holder the short data containing the bits we're * interested in * @return the value of holder with the specified bits set * to {@code 1} */ public short setShort(final short holder) { return (short) set(holder); } /** * <p>Sets the bits.

* * @param holder the byte data containing the bits we're * interested in * * @return the value of holder with the specified bits set * to {@code 1} */ public byte setByte(final byte holder) { return (byte) set(holder); } /** * <p>Sets a boolean BitField.

* * @param holder the int data containing the bits we're * interested in * @param flag indicating whether to set or clear the bits * @return the value of holder with the specified bits set or * cleared */ public int setBoolean(final int holder, final boolean flag) { return flag ? set(holder) : clear(holder); } /** * <p>Sets a boolean BitField.

* * @param holder the short data containing the bits we're * interested in * @param flag indicating whether to set or clear the bits * @return the value of holder with the specified bits set or * cleared */ public short setShortBoolean(final short holder, final boolean flag) { return flag ? setShort(holder) : clearShort(holder); } /** * <p>Sets a boolean BitField.

* * @param holder the byte data containing the bits we're * interested in * @param flag indicating whether to set or clear the bits * @return the value of holder with the specified bits set or * cleared */ public byte setByteBoolean(final byte holder, final boolean flag) { return flag ? setByte(holder) : clearByte(holder); } }

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