rulebasedcollator.java

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/* RuleBasedCollator.java -- Concrete Collator Class
   Copyright (C) 1998, 1999, 2001 Free Software Foundation, Inc.

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
the 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, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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02111-1307 USA.

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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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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this exception to your version of the library, but you are not
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exception statement from your version. */


package java.text;

import java.util.Vector;

/**
  * This class is a concrete subclass of <code>Collator</code> suitable
  * for string collation in a wide variety of languages.  An instance of
  * this class is normally returned by the <code>getInstance</code> method
  * of <code>Collator</code> with rules predefined for the requested
  * locale.  However, an instance of this class can be created manually
  * with any desired rules.
  * <p>
  * Rules take the form of a <code>String</code> with the following syntax
  * <ul>
  * <li> Modifier: '@' 
  * <li> Relation: '<' | ';' | ',' | '=' : <text>
  * <li> Reset: '&' : <text>
  * </ul>
  * The modifier character indicates that accents sort backward as is the
  * case with French.  The relational operators specify how the text 
  * argument relates to the previous term.  The relation characters have
  * the following meanings:
  * <ul>
  * <li>'<' - The text argument is greater than the prior term at the primary
  * difference level.
  * <li>';' - The text argument is greater than the prior term at the secondary
  * difference level.
  * <li>',' - The text argument is greater than the prior term at the tertiary
  * difference level.
  * <li>'=' - The text argument is equal to the prior term
  * </ul>
  * <p>
  * As for the text argument itself, this is any sequence of Unicode
  * characters not in the following ranges: 0x0009-0x000D, 0x0020-0x002F,
  * 0x003A-0x0040, 0x005B-0x0060, and 0x007B-0x007E. If these characters are 
  * desired, they must be enclosed in single quotes.  If any whitespace is 
  * encountered, it is ignored.  (For example, "a b" is equal to "ab").  
  * <p>
  * The reset operation inserts the following rule at the point where the
  * text argument to it exists in the previously declared rule string.  This
  * makes it easy to add new rules to an existing string by simply including
  * them in a reset sequence at the end.  Note that the text argument, or
  * at least the first character of it, must be present somewhere in the
  * previously declared rules in order to be inserted properly.  If this
  * is not satisfied, a <code>ParseException</code> will be thrown. 
  * <p>
  * This system of configuring <code>RuleBasedCollator</code> is needlessly
  * complex and the people at Taligent who developed it (along with the folks
  * at Sun who accepted it into the Java standard library) deserve a slow
  * and agonizing death.
  * <p>
  * Here are a couple of example of rule strings:
  * <p>
  * "< a < b < c" - This string says that a is greater than b which is 
  * greater than c, with all differences being primary differences.
  * <p>
  * "< a,A < b,B < c,C" - This string says that 'A' is greater than 'a' with
  * a tertiary strength comparison.  Both 'b' and 'B' are greater than 'a' and
  * 'A' during a primary strength comparison.  But 'B' is greater than 'b'
  * under a tertiary strength comparison.
  * <p>
  * "< a < c & a < b " - This sequence is identical in function to the 
  * "< a < b < c" rule string above.  The '&' reset symbol indicates that
  * the rule "< b" is to be inserted after the text argument "a" in the
  * previous rule string segment.
  * <p>
  * "< a < b & y < z" - This is an error.  The character 'y' does not appear
  * anywhere in the previous rule string segment so the rule following the
  * reset rule cannot be inserted.
  * <p>
  * For a description of the various comparison strength types, see the
  * documentation for the <code>Collator</code> class.
  * <p>
  * As an additional complication to this already overly complex rule scheme,
  * if any characters precede the first rule, these characters are considered
  * ignorable.  They will be treated as if they did not exist during 
  * comparisons.  For example, "- < a < b ..." would make '-' an ignorable
  * character such that the strings "high-tech" and "hightech" would
  * be considered identical.
  * <p>
  * A <code>ParseException</code> will be thrown for any of the following
  * conditions:
  * <ul>
  * <li>Unquoted punctuation characters in a text argument.
  * <li>A relational or reset operator not followed by a text argument
  * <li>A reset operator where the text argument is not present in
  * the previous rule string section.
  * </ul>
  *
  * @author Aaron M. Renn ([e-mail])
  */
public class RuleBasedCollator extends Collator
{

/*
 * Inner Classes
 */

class CollationElement
{
String char_seq;
int primary;
short secondary;
short tertiary;

CollationElement(String char_seq, int primary, short secondary, short tertiary)
{
  this.char_seq = char_seq;
  this.primary = primary;
  this.secondary = secondary;
  this.tertiary = tertiary;
}
 
} // inner class CollationElement

/*************************************************************************/

/*
 * Instance Variables
 */

/**
  * This the the original rule string.
  */
private String rules;

/**
  * This is the table of collation element values
  */
private Object[] ce_table;

/*************************************************************************/

/*
 * Constructors
 */

/**
  * This method initializes a new instance of <code>RuleBasedCollator</code>
  * with the specified collation rules.  Note that an application normally
  * obtains an instance of <code>RuleBasedCollator</code> by calling the
  * <code>getInstance</code> method of <code>Collator</code>.  That method
  * automatically loads the proper set of rules for the desired locale.
  *
  * @param rules The collation rule string.
  *
  * @exception ParseException If the rule string contains syntax errors.
  */
public
RuleBasedCollator(String rules) throws ParseException
{
  this.rules = rules;

  if (rules.equals(""))
    throw new IllegalArgumentException("Empty rule set");

  Vector v = new Vector();
  boolean ignore_chars = true;
  int primary_seq = 0;
  short secondary_seq = 0;
  short tertiary_seq = 0;
  StringBuffer sb = new StringBuffer("");
  for (int i = 0; i < rules.length(); i++)
    {
      char c = rules.charAt(i);

      // Check if it is a whitespace character
      if (((c >= 0x09) && (c <= 0x0D)) || (c == 0x20))
        continue;

      // Primary difference
      if (c == '<')
        {
          ignore_chars = false;
          secondary_seq = 0;
          tertiary_seq = 0;
          ++primary_seq;

          CollationElement e = new CollationElement(sb.toString(), primary_seq,
                                                    secondary_seq,
                                                    tertiary_seq);
          v.add(e);
          sb.setLength(0);
          continue;
        }

      // Secondary difference
      if (c == ';')
        {
          if (primary_seq == 0)
            throw new ParseException(rules, i);

          ++secondary_seq;
          tertiary_seq = 0;

          CollationElement e = new CollationElement(sb.toString(), primary_seq,
                                                    secondary_seq,
                                                    tertiary_seq);
          v.add(e);
          sb.setLength(0);
          continue;
        }

      // Tertiary difference
      if (c == ',')
        {
          if (primary_seq == 0)
            throw new ParseException(rules, i);

          ++tertiary_seq;

          CollationElement e = new CollationElement(sb.toString(), primary_seq,
                                                    secondary_seq,
                                                    tertiary_seq);
          v.add(e);
          sb.setLength(0);
          continue;
        }

      // Is equal to
      if (c == '=')
        {
          if (primary_seq == 0)
            throw new ParseException(rules, i);

          CollationElement e = new CollationElement(sb.toString(), primary_seq,
                                                    secondary_seq,
                                                    tertiary_seq);
          v.add(e);
          sb.setLength(0);
          continue;
        }

      // Sort accents backwards
      if (c == '@')
        {
          throw new ParseException("French style accents not implemented yet", 0);
        }

      // Reset command
      if (c == '&')
        {