/*
 * 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:
 * </p>
 *
 * <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.
	 * </p>
	 *
	 * @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 ? 0 : Integer.numberOfTrailingZeros(mask);
	}

	/**
	 * <p>
	 * Clears the bits.
	 * </p>
	 *
	 * @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.
	 * </p>
	 *
	 * @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>
	 * Clears the bits.
	 * </p>
	 *
	 * @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>
	 * Obtains the value for the specified BitField, unshifted.
	 * </p>
	 *
	 * @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.
	 * </p>
	 *
	 * @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>
	 * 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, 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>
	 * Returns whether all of the bits are set or not.
	 * </p>
	 *
	 * <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>
	 * Returns whether the field is set or not.
	 * </p>
	 *
	 * <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>
	 * Sets the bits.
	 * </p>
	 *
	 * @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 a boolean BitField.
	 * </p>
	 *
	 * @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 the bits.
	 * </p>
	 *
	 * @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.
	 * </p>
	 *
	 * @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);
	}

	/**
	 * <p>
	 * Sets the bits.
	 * </p>
	 *
	 * @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 a boolean BitField.
	 * </p>
	 *
	 * @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>
	 * Replaces the bits with new values.
	 * </p>
	 *
	 * @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>
	 * Replaces the bits with new values.
	 * </p>
	 *
	 * @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);
	}

}
