/* Queue.java -- a token queue.   Copyright (C) 2005 Free Software Foundation, Inc.This file is part of GNU Classpath.GNU Classpath is free software; you can redistribute it and/or modifyit under the terms of the GNU General Public License as published bythe Free Software Foundation; either version 2, or (at your option)any later version.GNU Classpath is distributed in the hope that it will be useful, butWITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNUGeneral Public License for more details.You should have received a copy of the GNU General Public Licensealong with GNU Classpath; see the file COPYING.  If not, write to theFree Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA02110-1301 USA.Linking this library statically or dynamically with other modules ismaking a combined work based on this library.  Thus, the terms andconditions of the GNU General Public License cover the wholecombination.As a special exception, the copyright holders of this library give youpermission to link this library with independent modules to produce anexecutable, regardless of the license terms of these independentmodules, and to copy and distribute the resulting executable underterms of your choice, provided that you also meet, for each linkedindependent module, the terms and conditions of the license of thatmodule.  An independent module is a module which is not derived fromor based on this library.  If you modify this library, you may extendthis exception to your version of the library, but you are notobligated to do so.  If you do not wish to do so, delete thisexception statement from your version. */package gnu.javax.swing.text.html.parser.support.low;import java.util.Arrays;/** * A token queue. * @author Audrius Meskauskas, Lithuania (AudriusA@Bioinformatics.org) */public class Queue{  Token[] m = new Token[ 64 ];  int a = 0;  int b = 0;  /**   * True for the empty queue.   */  public boolean isEmpty()  {    return size() == 0;  }  /**   *  Add this trace to the end of the queue.   */  public void add(Token u)  {    if (a < m.length)      {        m [ a ] = u;        a++;      }    else // The end of array has been reached.      {        if (b > 0) // If some elements were deleted from the start of the queue, shift.          {            int d = b;            System.arraycopy(m, b, m, 0, a - b);            b = b - d;            a = a - d;            m [ a ] = u;            a++;          }        else // Enlarge the queue, doubling the size.          {            int n = m.length * 2;            Token[] nm = new Token[ 2 * n ];            System.arraycopy(m, 0, nm, 0, m.length);            Arrays.fill(m, null);            nm [ a ] = u;            m = nm;            a++;          }      }  }  /**   * Clear the queue.   */  public void clear()  {    a = b = 0;    Arrays.fill(m, null);  }  /**   * Read the value ahead. 0 is the value that will be returned with   * the following next. This method does not remove values from the   * queue. To test if there is enough tokens in the queue, size() must   * be checked before calling this method.   */  public Token get(int ahead)  {    int p = b + ahead;    if (p < a)      return m [ p ];    else      throw new ArrayIndexOutOfBoundsException("Not enough tokens");  }  /**   * Read the oldest value from the queue and remove this value from   * the queue.   */  public Token next()  {    if (a == b)      throw new ArrayIndexOutOfBoundsException("queue empty");    Token r = m [ b ];    m [ b ] = null;    b++;    return r;  }  /**   * Size of the queue.   */  public int size()  {    return a - b;  }}