package org.jscsi.target.util;

 /**

  * A class for serial number arithmetics, as defined in <code>[RFC 1982]</code>, with <code>SERIAL_BITS = 32</code>.

  * <p>

  * Unlike the original algorithm, this implementation is based on unsigned subtraction, resolving the issue of undefined

  * comparisons, however introducing one additional oddity - each member of a pair of serial numbers with a wrapped

  * distance of <code>2^(SERIAL_BITS - 1)</code> will be considered less than (and greater than) the other one.

  * 

  * @author Andreas Ergenzinger

  */

 public final class SerialArithmeticNumber {

     /**

      * The signed integer representation of the serial arithmetic number.

      */

     private int value;

     /**

      * Creates a new {@link SerialArithmeticNumber} with a starting {@link #value} of zero.

      */

     public SerialArithmeticNumber () {

         this(0);

     }

     /**

      * Creates a new {@link SerialArithmeticNumber} with the specified starting {@link #value}.

      * 

      * @param value the initial {@link #value}

      */

     public SerialArithmeticNumber (final int value) {

         this.value = value;

     }

     /**

      * Increments the {@link SerialArithmeticNumber}'s {@link #value} by one.

      */

     public void increment () {

         ++value;

     }

     /**

      * Returns <code>true</code> if the parameter matches the {@link #value} and <code>false</code> if it does not.

      * 

      * @param serialArithmeticNumber the serial arithmetic number to match

      * @return <code>true</code> if the parameter matches the {@link #value} and <code>false</code> if it does not

      */

     public boolean equals (final int serialArithmeticNumber) {

         return value == serialArithmeticNumber;

     }

     /**

      * Returns <code>true</code> if the parameter is less than the {@link #value} in serial number arithmetics and

      * <code>false</code> if it is not.

      * 

      * @param serialArithmeticNumber the serial arithmetic number to match

      * @return <code>true</code> if the parameter is less than the {@link #value} in serial number arithmetics and

      *         <code>false</code> if it is not

      */

     public boolean lessThan (final int serialArithmeticNumber) {

         if (value - serialArithmeticNumber < 0) return true;

         return false;

     }

     /**

      * Returns <code>true</code> if the parameter is greater than the {@link #value} in serial number arithmetics and

      * <code>false</code> if it is not.

      * 

      * @param serialArithmeticNumber the serial arithmetic number to match

      * @return <code>true</code> if the parameter is greater than the {@link #value} in serial number arithmetics and

      *         <code>false</code> if it is not

      */

     public boolean greaterThan (final int serialArithmeticNumber) {

         if (serialArithmeticNumber - value < 0) return true;

         return false;

     }

     /**

      * Returns the {@link SerialArithmeticNumber}'s {@link #value}.

      * 

      * @return the {@link #value}

      */

     public int getValue () {

         return value;

     }

 }