# BitSelector.java

    /*
    ** Module   :BitSelector.java
    ** Abstract :BitSelector, a subclass of BitField (one bit set to 1 at a time)
    **
    ** Copyright (c) 2005-2017, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- -T- --JPRM-- ----------------Description-----------------
    ** 001 SIY 20050216 ADD  @20016  Created initial implementation
    ** 002 SIY 20050310 CHG  @20355  Organized imports and reordered methods.
    ** 003 SIY 20050323 CHG  @20469  Fixed formatting.
    ** 004 SIY 20050328 CHG  @20575  Fixed comments and other minor cleanups.
    ** 005 SIY 20050428 CHG  @21008  Fixed comments and formatting.
    ** 006 SIY 20050515 CHG  @21188  Extended comments.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program is distributed in the hope that it will be useful,
    ** but WITHOUT ANY WARRANTY; without even the implied warranty of
    ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ** GNU Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
    **   2. No Misrepresentation of Affiliation.
    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
    **     You may not represent yourself for publicity purposes as associated with
    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.directory;

    import java.util.BitSet;

    /**
     * BitSelector, a subclass of BitField which allows only one bit set to 1 at a
     * time.
     * <p>
     * The main purpose of this class is to provide Java representation of the
     * <code>Bit Selector</code> attribute type.
     *
     * @author  SIY
     * @version 1.0
     */
    public class BitSelector
    extends BitField
    {
       /**
        * Construct an instance of specified width and with specified bit set to
        * <code>true</code>.
        *
        * @param   width
        *          BitSelector width.
        * @param   index
        *          Set bit index.
        */
       public BitSelector(int width, int index)
       {
          super(width);
          set(index);
       }

       /**
        * Parse <code>String</code> like 00000100 and create an instance of
        * <code>BitSelector</code>.
        *
        * @param   str
        *          Source string.
        * @return  New <code>BitSelector</code> instance or <code>null</code>
        *          if source string does not contain properly formatted bit field.
        */
       public static BitField valueOf(String str)
       {
          if (str == null || str.length() == 0)
             return null;

          BitField field = BitField.valueOf(str);

          if (field == null)
             return null;

          if (field.cardinality() != 1)
             return null;

          BitSelector res = new BitSelector(field.size(), field.nextSetBit(0));

          return res;
       }

       /**
        * This method is not allowed for use.
        *
        * @param   set
        *          Ignored parameter.
        * @throws  IllegalArgumentException
        *          thrown for any try to call this method.
        */
       public void and(BitSet set)
       {
          disabled();
          super.and(set);
       }

       /**
        * This method is not allowed for use.
        *
        * @param   set
        *          Ignored parameter.
        * @throws  IllegalArgumentException
        *          thrown for any try to call this method.
        */
       public void andNot(BitSet set)
       {
          disabled();
          super.andNot(set);
       }

       /**
        * This method is not allowed for use.
        *
        * @throws  IllegalArgumentException
        *          thrown for any try to call this method.
        */
       public void clear()
       {
          disabled();
          super.clear();
       }

       /**
        * This method is not allowed for use.
        *
        * @param   index
        *          Ignored parameter.
        * @throws  IllegalArgumentException
        *          thrown for any try to call this method.
        */
       public void clear(int index)
       {
          disabled();
          super.clear(index);
       }

       /**
        * This method is not allowed for use.
        *
        * @param   from
        *          Ignored parameter.
        * @param   to
        *          Ignored parameter.
        * @throws  IllegalArgumentException
        *          thrown for any try to call this method.
        */
       public void clear(int from, int to)
       {
          disabled();
          super.clear(from, to);
       }

       /**
        * This method is not allowed for use.
        *
        * @param   index
        *          Ignored parameter.
        * @throws  IllegalArgumentException
        *          thrown for any try to call this method.
        */
       public void flip(int index)
       {
          disabled();
          super.flip(index);
       }

       /**
        * This method is not allowed for use.
        *
        * @param   from
        *          Ignored parameter.
        * @param   to
        *          Ignored parameter.
        * @throws  IllegalArgumentException
        *          thrown for any try to call this method.
        */
       public void flip(int from, int to)
       {
          disabled();
          super.flip(from, to);
       }

       /**
        * Set specified bit into <code>true</code>.
        *
        * @param   index
        *          The index of the bit to set.
        * @throws  IndexOutOfBoundsException
        *          if the specified index is negative or exceeds BitSelector
        *          width.
        */
       public void set(int index)
       {
          int pos = nextSetBit(0);

          if (pos == -1) //First time bit is set
          {
             super.set(index);
             return;
          }

          if (pos == index) //Already set
             return;

          super.set(index); //If exception is thrown then state is preserved
          super.clear(pos); //Finally clear bit
       }

       /**
        * Set specified bit into specified value.
        *
        * @param   index
        *          The index of the bit to set
        * @param   val
        *          New bit value.
        * @throws  IndexOutOfBoundsException
        *          if the specified index is negative or exceeds BitSelector
        *          width.
        */
       public void set(int index, boolean val)
       {
          if (!val)
             throw new IllegalArgumentException("Only true is allowed.");

          set(index);
       }

       /**
        * Set specified range of bits into <code>true</code>.
        *
        * @param   from
        *          The index of the first bit in range.
        * @param   to
        *          The index of the last bit in range.
        * @throws  IndexOutOfBoundsException
        *          if the specified range does not fit into BitSelector width.
        */
       public void set(int from, int to)
       {
          if (to > (from + 1))
             throw new IllegalArgumentException("Range is too wide.");

          set(from);
       }

       /**
        * Set specified range of bits into specified value. The range width must
        * be 1 and value must be <code>true</code>.
        *
        * @param   from
        *          The index of the first bit in range.
        * @param   to
        *          The index of the last bit in range.
        * @param   val
        *          New value for the range.
        * @throws  IndexOutOfBoundsException
        *          if the specified range does not fit into BitSelector width.
        */
       public void set(int from, int to, boolean val)
       {
          if (!val)
             throw new IllegalArgumentException("Only true is allowed.");

          set(from, to);
       }

       /**
        * Performs a logical XOR of this bit field with the argument bit set.
        *
        * @param   set
        *          A bit set to perform operation with.
        * @throws  IndexOutOfBoundsException
        *          if the specified set is too wide.
        */
       public void xor(BitSet set)
       {
          if (set.cardinality() != 1 || set.nextSetBit(0) == nextSetBit(0))
             throw new IllegalArgumentException(
                 "Too many bits set or bit positions the same in both selectors");

          super.xor(set);
       }

       /**
        * Just throw an exception
        *
        * @throws  IllegalArgumentException
        *          if method is called.
        */
       private void disabled()
       {
          throw new IllegalArgumentException(
                                          "No calls to this method are allowed.");
       }
    }