libjava/java/text/CollationElementIterator.java

/* CollationElementIterator.java -- Walks through collation elements
   Copyright (C) 1998, 1999, 2001, 2002, 2003  Free Software Foundation

This file is part of GNU Classpath.

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it under the terms of the GNU General Public License as published by
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Linking this library statically or dynamically with other modules is
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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package java.text;

/* Written using "Java Class Libraries", 2nd edition, plus online
 * API docs for JDK 1.2 from http://www.javasoft.com.
 * Status: Believed complete and correct to JDK 1.1.
 */

/**
 * This class walks through the character collation elements of a 
 * <code>String</code> as defined by the collation rules in an instance of 
 * <code>RuleBasedCollator</code>.  There is no public constructor for
 * this class.  An instance is created by calling the
 * <code>getCollationElementIterator</code> method on 
 * <code>RuleBasedCollator</code>.
 *
 * @author Aaron M. Renn <arenn@urbanophile.com>
 * @author Tom Tromey <tromey@cygnus.com>
 * @author Guilhem Lavaux <guilhem.lavaux@free.fr>
 */
public final class CollationElementIterator
{
  /**
   * This is a constant value that is returned to indicate that the end of 
   * the string was encountered.
   */
  public static final int NULLORDER = -1;

  /**
   * This is the RuleBasedCollator this object was created from.
   */
  RuleBasedCollator collator;

  /**
   * This is the String that is being iterated over.
   */
  String text;

  /**
   * This is the index into the String where we are currently scanning.
   */
  int textIndex;

  // A piece of lookahead.
  boolean lookahead_set;
  int lookahead;

  /**
   * This method initializes a new instance of <code>CollationElementIterator</code>
   * to iterate over the specified <code>String</code> using the rules in the
   * specified <code>RuleBasedCollator</code>.
   *
   * @param collator The <code>RuleBasedCollation</code> used for calculating collation values
   * @param text The <code>String</code> to iterate over.
   */
  CollationElementIterator(RuleBasedCollator collator, String text)
  {
    this.collator = collator;
    
    setText (text);    
  }

  /**
   * This method returns the collation ordering value of the next character sequence
   * in the string (it may be an extended character following collation rules).
   * This method will return <code>NULLORDER</code> if the
   * end of the string was reached.
   *
   * @return The collation ordering value.
   */
  public int next()
  {
    if (textIndex == text.length())
      return NULLORDER;

    return collator.ceiNext (this);
  }

  /**
   * This method returns the primary order value for the given collation
   * value.
   *
   * @param value The collation value returned from <code>next()</code> or <code>previous()</code>.
   *
   * @return The primary order value of the specified collation value.  This is the high 16 bits.
   */
  public static final int primaryOrder(int order)
  {
    // From the JDK 1.2 spec.
    return order >>> 16;
  }

  /**
   * This method resets the internal position pointer to read from the
   * beginning of the <code>String again.
   */
  public void reset()
  {
    textIndex = 0;
  }

  /**
   * This method returns the secondary order value for the given collation
   * value.
   *
   * @param value The collation value returned from <code>next()</code> or <code>previous()</code>.
   *
   * @return The secondary order value of the specified collation value.  This is the bits 8-15.
   */
  public static final short secondaryOrder(int order)
  {
    // From the JDK 1.2 spec.
    return (short) ((order >>> 8) & 255);
  }

  /**
   * This method returns the tertiary order value for the given collation
   * value.
   *
   * @param value The collation value returned from <code>next()</code> or <code>previous()</code>.
   *
   * @return The tertiary order value of the specified collation value.  This is the low eight bits.
   */
  public static final short tertiaryOrder(int order)
  {
    // From the JDK 1.2 spec.
    return (short) (order & 255);
  }

  /**
   * This method sets the <code>String</code> that it is iterating over
   * to the specified <code>String</code>.
   *
   * @param text The new <code>String</code> to iterate over.
   *
   * @since 1.2
   */
  public void setText(String text)
  {
    this.text = text;
    this.textIndex = 0;
    this.lookahead_set = false;
    this.lookahead = 0;
  }

  /**
   * This method returns the current offset into the <code>String</code>
   * that is being iterated over.
   *
   * @return The iteration index position.
   *
   * @since 1.2
   */
  public int getOffset()
  {
    return textIndex;
  }
}