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.lang;
  
  /**
   * <p>Operations on bit-mapped fields.</p>
   *
   * @author Apache Jakarta POI
   * @author Scott Sanders (sanders at apache dot org)
   * @author Marc Johnson (mjohnson at apache dot org)
   * @author Andrew C. Oliver (acoliver at apache dot org)
   * @author Stephen Colebourne
   * @author Pete Gieser
   * @author Gary Gregory
   * @since 2.0
   * @version $Id: BitField.java 437554 2006-08-28 06:21:41Z bayard $
   */
  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(int mask) {
          _mask = mask;
          int count = 0;
          int bit_pattern = mask;
  
          if (bit_pattern != 0) {
              while ((bit_pattern & 1) == 0) {
                  count++;
                  bit_pattern >>= 1;
              }
          }
          _shift_count = count;
      }
  
      /**
       * <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(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(short holder) {
          return (short) getValue(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(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(short holder) {
          return (short) getRawValue(holder);
      }
  
      /**
       * <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</code> if any of the bits are set,
       *  else <code>false</code>
       */
      public boolean isSet(int holder) {
          return (holder & _mask) != 0;
      }
  
      /**
       * <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</code>.</p>
       *
       * @param holder the int data containing the bits we're
       *  interested in
       * @return <code>true</code> if all of the bits are set,
       *  else <code>false</code>
       */
      public boolean isAllSet(int holder) {
          return (holder & _mask) == _mask;
      }
  
      /**
       * <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(int holder, int value) {
          return (holder & ~_mask) | ((value << _shift_count) & _mask);
      }
  
      /**
       * <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(short holder, short value) {
          return (short) setValue(holder, value);
      }
  
      /**
       * <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</code>)
       */
      public int clear(int holder) {
          return holder & ~_mask;
      }
  
      /**
       * <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</code>)
       */
      public short clearShort(short holder) {
          return (short) clear(holder);
      }
  
      /**
       * <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</code>)
       */
      public byte clearByte(byte holder) {
          return (byte) clear(holder);
      }
  
      /**
       * <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</code>
       */
      public int set(int holder) {
          return holder | _mask;
      }
  
      /**
       * <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</code>
       */
      public short setShort(short holder) {
          return (short) set(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</code>
       */
      public byte setByte(byte holder) {
          return (byte) set(holder);
      }
  
      /**
       * <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(int holder, boolean flag) {
          return flag ? set(holder) : clear(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(short holder, boolean flag) {
          return flag ? setShort(holder) : clearShort(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(byte holder, boolean flag) {
          return flag ? setByte(holder) : clearByte(holder);
      }
  
  }
  