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/*
* 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;
/**
* 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}.
*
* Each {@link 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.
*
* As an example, consider a car painting machine that accepts
* paint instructions as integers. Bit fields can be used to encode this:
*
*
* // 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);
*
*
* Using these {@link BitField} instances, a paint instruction can be
* encoded into an integer:
*
*
* int paintInstruction = 0;
* paintInstruction = red.setValue(paintInstruction, 35);
* paintInstruction = green.setValue(paintInstruction, 100);
* paintInstruction = blue.setValue(paintInstruction, 255);
*
*
* Flags and data can be retrieved from the integer:
*
*
* // 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
*
*
* @since 2.0
*/
public class BitField {
private final int mask;
private final int shiftCount;
/**
* 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) {
this.mask = mask;
this.shiftCount = mask == 0 ? 0 : Integer.numberOfTrailingZeros(mask);
}
/**
* 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;
}
/**
* 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);
}
/**
* 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);
}
/**
* 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;
}
/**
* 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);
}
/**
* Obtains the value for the specified BitField, appropriately
* shifted right, as a short.
*
* 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).
*
* @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);
}
/**
* Obtains the value for the specified BitField, appropriately
* shifted right.
*
* 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).
*
* @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) >> shiftCount;
}
/**
* Returns whether all of the bits are set or not.
*
* 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}.
*
* @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;
}
/**
* Returns whether the field is set or not.
*
* 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.
*
* @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;
}
/**
* 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;
}
/**
* 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);
}
/**
* 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);
}
/**
* 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);
}
/**
* 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);
}
/**
* 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);
}
/**
* 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);
}
/**
* 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 << shiftCount) & mask);
}
}