CollationElementIterator.java

/* CollationElementIterator.java -- Walks through collation elements
   Copyright (C) 1998, 1999, 2001, 2002, 2003, 2004  Free Software Foundation

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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WITHOUT ANY WARRANTY; without even the implied warranty of
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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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
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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package java.text;

import gnu.java.lang.CPStringBuilder;

import java.util.ArrayList;

/* 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.
   */
  CharacterIterator text;

  /**
   * This is the index into the collation decomposition where we are currently scanning.
   */
  int index;

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

  /**
   * Array containing the collation decomposition of the
   * text given to the constructor.
   */
  private RuleBasedCollator.CollationElement[] text_decomposition;

  /**
   * Array containing the index of the specified block.
   */
  private int[] text_indexes;

  /**
   * 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 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 character iterator to iterate over.
   */
  CollationElementIterator(RuleBasedCollator collator, CharacterIterator text)
  {
    this.collator = collator;

    setText (text);
  }

  RuleBasedCollator.CollationElement nextBlock()
  {
    if (index >= text_decomposition.length)
      return null;

    RuleBasedCollator.CollationElement e = text_decomposition[index];

    textIndex = text_indexes[index+1];

    index++;

    return e;
  }

  RuleBasedCollator.CollationElement previousBlock()
  {
    if (index == 0)
      return null;

    index--;
    RuleBasedCollator.CollationElement e = text_decomposition[index];

    textIndex = text_indexes[index+1];

    return e;
  }

  /**
   * 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()
  {
    RuleBasedCollator.CollationElement e = nextBlock();

    if (e == null)
      return NULLORDER;

    return e.getValue();
  }

  /**
   * This method returns the collation ordering value of the previous character
   * in the string.  This method will return <code>NULLORDER</code> if the
   * beginning of the string was reached.
   *
   * @return The collation ordering value.
   */
  public int previous()
  {
    RuleBasedCollator.CollationElement e = previousBlock();

    if (e == null)
      return NULLORDER;

    return e.getValue();
  }

  /**
   * This method returns the primary order value for the given collation
   * value.
   *
   * @param order 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 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</code> again.
   */
  public void reset()
  {
    index = 0;
    textIndex = 0;
  }

  /**
   * This method returns the secondary order value for the given collation
   * value.
   *
   * @param order 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 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 order 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 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)
  {
    int idx = 0;
    int idx_idx = 0;
    int alreadyExpanded = 0;
    int idxToMove = 0;

    this.text = new StringCharacterIterator(text);
    this.index = 0;

    String work_text = text.intern();

    ArrayList a_element = new ArrayList();
    ArrayList a_idx = new ArrayList();

    // Build element collection ordered as they come in "text".
    while (idx < work_text.length())
      {
        String key, key_old;

        Object object = null;
        int p = 1;

        // IMPROVE: use a TreeMap with a prefix-ordering rule.
        key_old = key = null;
        do
          {
            if (object != null)
              key_old = key;
            key = work_text.substring (idx, idx+p);
            object = collator.prefix_tree.get (key);
            if (object != null && idx < alreadyExpanded)
              {
                RuleBasedCollator.CollationElement prefix = (RuleBasedCollator.CollationElement)object;
                if (prefix.expansion != null &&
                    prefix.expansion.startsWith(work_text.substring(0, idx)))
                {
                  object = null;
                  key = key_old;
                }
              }
            p++;
          }
        while (idx+p <= work_text.length());

        if (object == null)
          key = key_old;

        RuleBasedCollator.CollationElement prefix =
          (RuleBasedCollator.CollationElement) collator.prefix_tree.get (key);

        /*
         * First case: There is no such sequence in the database.
         * We will have to build one from the context.
         */
        if (prefix == null)
          {
            /*
             * We are dealing with sequences in an expansion. They
             * are treated as accented characters (tertiary order).
             */
            if (alreadyExpanded > 0)
              {
                RuleBasedCollator.CollationElement e =
                  collator.getDefaultAccentedElement (work_text.charAt (idx));

                a_element.add (e);
                a_idx.add (new Integer(idx_idx));
                idx++;
                alreadyExpanded--;
                if (alreadyExpanded == 0)
                  {
                    /* There is not any characters left in the expansion set.
                     * We can increase the pointer in the source string.
                     */
                    idx_idx += idxToMove;
                    idxToMove = 0;
                  }
                else
                  idx_idx++;
              }
            else
              {
                /* This is a normal character. */
                RuleBasedCollator.CollationElement e =
                  collator.getDefaultElement (work_text.charAt (idx));
                Integer i_ref = new Integer(idx_idx);

                /* Don't forget to mark it as a special sequence so the
                 * string can be ordered.
                 */
                a_element.add (RuleBasedCollator.SPECIAL_UNKNOWN_SEQ);
                a_idx.add (i_ref);
                a_element.add (e);
                a_idx.add (i_ref);
                idx_idx++;
                idx++;
              }
            continue;
          }

        /*
         * Second case: Here we have found a matching sequence.
         * Here we have an expansion string prepend it to the "work text" and
         * add the corresponding sorting element. We must also mark
         */
        if (prefix.expansion != null)
          {
            work_text = prefix.expansion
              + work_text.substring (idx+prefix.key.length());
            idx = 0;
            a_element.add (prefix);
            a_idx.add (new Integer(idx_idx));
            if (alreadyExpanded == 0)
              idxToMove = prefix.key.length();
            alreadyExpanded += prefix.expansion.length()-prefix.key.length();
          }
        else
          {
            /* Third case: the simplest. We have got the prefix and it
             * has not to be expanded.
             */
            a_element.add (prefix);
            a_idx.add (new Integer(idx_idx));
            idx += prefix.key.length();
            /* If the sequence is in an expansion, we must decrease the
             * counter.
             */
            if (alreadyExpanded > 0)
              {
                alreadyExpanded -= prefix.key.length();
                if (alreadyExpanded == 0)
                  {
                    idx_idx += idxToMove;
                    idxToMove = 0;
                  }
              }
            else
              idx_idx += prefix.key.length();
          }
      }

    text_decomposition = (RuleBasedCollator.CollationElement[])
           a_element.toArray(new RuleBasedCollator.CollationElement[a_element.size()]);
    text_indexes = new int[a_idx.size()+1];
    for (int i = 0; i < a_idx.size(); i++)
      {
        text_indexes[i] = ((Integer)a_idx.get(i)).intValue();
      }
    text_indexes[a_idx.size()] = text.length();
  }

  /**
   * This method sets the <code>String</code> that it is iterating over
   * to the <code>String</code> represented by the specified
   * <code>CharacterIterator</code>.
   *
   * @param source The <code>CharacterIterator</code> containing the new
   * <code>String</code> to iterate over.
   */
  public void setText(CharacterIterator source)
  {
    CPStringBuilder expand = new CPStringBuilder();

    // For now assume we read from the beginning of the string.
    for (char c = source.first();
         c != CharacterIterator.DONE;
         c = source.next())
      expand.append(c);

    setText(expand.toString());
  }

  /**
   * 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;
  }

  /**
   * This method sets the iteration index position into the current
   * <code>String</code> to the specified value.  This value must not
   * be negative and must not be greater than the last index position
   * in the <code>String</code>.
   *
   * @param offset The new iteration index position.
   *
   * @exception IllegalArgumentException If the new offset is not valid.
   */
  public void setOffset(int offset)
  {
    if (offset < 0)
      throw new IllegalArgumentException("Negative offset: " + offset);

    if (offset > (text.getEndIndex() - 1))
      throw new IllegalArgumentException("Offset too large: " + offset);

    for (index = 0; index < text_decomposition.length; index++)
      {
        if (offset <= text_indexes[index])
          break;
      }
    /*
     * As text_indexes[0] == 0, we should not have to take care whether index is
     * greater than 0. It is always.
     */
    if (text_indexes[index] == offset)
      textIndex = offset;
    else
      textIndex = text_indexes[index-1];
  }

  /**
   * This method returns the maximum length of any expansion sequence that
   * ends with the specified collation order value.  (Whatever that means).
   *
   * @param value The collation order value
   *
   * @return The maximum length of an expansion sequence.
   */
  public int getMaxExpansion(int value)
  {
    return 1;
  }
}