rulebasedcollator.java

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// RuleBasedCollator.java - Concrete class for locale-based string compare.

/* Copyright (C) 1999, 2000, 2001  Free Software Foundation

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

package java.text;

import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;

/**
 * @author Tom Tromey <[e-mail]>
 * @date March 25, 1999
 */
/* 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
 */

final class RBCElement
{
  String key;
  char relation;

  RBCElement (String key, char relation)
  {
    this.key = key;
    this.relation = relation;
  }
}

public class RuleBasedCollator extends Collator
{
  public Object clone ()
  {
    RuleBasedCollator c = (RuleBasedCollator) super.clone ();
    c.map = (Hashtable) map.clone ();
    c.prefixes = (Hashtable) map.clone ();
    return c;
  }

  // A helper for CollationElementIterator.next().
  int ceiNext (CollationElementIterator cei)
  {
    if (cei.lookahead_set)
      {
	cei.lookahead_set = false;
	return cei.lookahead;
      }

    int save = cei.index;
    int max = cei.text.length();
    String s = null;

    // It is possible to have a case where `abc' has a mapping, but
    // neither `ab' nor `abd' do.  In this case we must treat `abd' as
    // nothing special.
    boolean found = false;

    int i;
    for (i = save + 1; i <= max; ++i)
      {
	s = cei.text.substring(save, i);
	if (prefixes.get(s) == null)
	  break;
	found = true;
      }
    // Assume s != null.

    Object obj = map.get(s);
    // The special case.
    while (found && obj == null && s.length() > 1)
      {
	--i;
	s = cei.text.substring(save, i);
	obj = map.get(s);
      }

    // Update state.
    cei.index = i;

    if (obj == null)
      {
	// This idea, and the values, come from JDK.
	// assert (s.length() == 1)
	cei.lookahead_set = true;
	cei.lookahead = s.charAt(0) << 8;
	return 0x7fff << 16;
      }

    return ((Integer) obj).intValue();
  }

  // A helper for compareTo() that returns the next character that has
  // a nonzero ordering at the indicated strength.  This is also used
  // in CollationKey.
  static final int next (CollationElementIterator iter, int strength)
  {
    while (true)
      {
	int os = iter.next();
	if (os == CollationElementIterator.NULLORDER)
	  return os;
	int c = 0;
	switch (strength)
	  {
	  case PRIMARY:
	    c = os & ~0xffff;
	    break;
	  case SECONDARY:
	    c = os & ~0x00ff;
	    break;
	  case TERTIARY:
	  case IDENTICAL:
	    c = os;
	    break;
	  }
	if (c != 0)
	  return c;
      }
  }

  public int compare (String source, String target)
  {
    CollationElementIterator cs, ct;

    cs = new CollationElementIterator (source, this);
    ct = new CollationElementIterator (target, this);

    while (true)
      {
	int os = next (cs, strength);
	int ot = next (ct, strength);

	if (os == CollationElementIterator.NULLORDER
	    && ot == CollationElementIterator.NULLORDER)
	  break;
	else if (os == CollationElementIterator.NULLORDER)
	  {
	    // Source string is shorter, so return "less than".
	    return -1;
	  }
	else if (ot == CollationElementIterator.NULLORDER)
	  {
	    // Target string is shorter, so return "greater than".
	    return 1;
	  }

	if (os != ot)
	  return os - ot;
      }

    return 0;
  }

  public boolean equals (Object obj)
  {
    if (! (obj instanceof RuleBasedCollator) || ! super.equals(obj))
      return false;
    RuleBasedCollator rbc = (RuleBasedCollator) obj;
    // FIXME: this is probably wrong.  Instead we should compare maps
    // directly.
    return (frenchAccents == rbc.frenchAccents
	    && rules.equals(rbc.rules));
  }

  public CollationElementIterator getCollationElementIterator (String source)
  {
    StringBuffer expand = new StringBuffer (source.length());
    int max = source.length();
    for (int i = 0; i < max; ++i)
      decomposeCharacter (source.charAt(i), expand);
    return new CollationElementIterator (expand.toString(), this);
  }

  public CollationElementIterator getCollationElementIterator (CharacterIterator source)
  {
    StringBuffer expand = new StringBuffer ();
    for (char c = source.first ();
	 c != CharacterIterator.DONE;
	 c = source.next ())
      decomposeCharacter (c, expand);

    return new CollationElementIterator (expand.toString(), this);
  }

  public CollationKey getCollationKey (String source)
  {
    return new CollationKey (getCollationElementIterator (source), source,
			     strength);
  }

  public String getRules ()
  {
    return rules;
  }

  public int hashCode ()
  {
    return (frenchAccents ? 1231 : 1237
	    ^ rules.hashCode()
	    ^ map.hashCode()
	    ^ prefixes.hashCode());
  }

  private final boolean is_special (char c)
  {
    // Rules from JCL book.
    return ((c >= 0x0009 && c <= 0x000d)
	    || (c >= 0x0020 && c <= 0x002f)
	    || (c >= 0x003a && c <= 0x0040)
	    || (c >= 0x005b && c <= 0x0060)
	    || (c >= 0x007b && c <= 0x007e));
  }

  private final int text_argument (String rules, int index,
				   StringBuffer result)
  {
    result.setLength(0);
    int len = rules.length();
    while (index < len)
      {
	char c = rules.charAt(index);
	if (c == '\'' && index + 2 < len
	    && rules.charAt(index + 2) == '\''
	    && is_special (rules.charAt(index + 1)))
	  index += 2;
	else if (is_special (c) || Character.isWhitespace(c))
	  return index;
	result.append(c);
	++index;
      }
    return index;
  }

  public RuleBasedCollator (String rules) throws ParseException
  {
    this.rules = rules;
    this.frenchAccents = false;

    // We keep each rule in order in a vector.  At the end we traverse
    // the vector and compute collation values from it.
    int insertion_index = 0;
    Vector vec = new Vector ();

    StringBuffer argument = new StringBuffer ();

    int len = rules.length();
    for (int index = 0; index < len; ++index)
      {
	char c = rules.charAt(index);

	// Just skip whitespace.
	if (Character.isWhitespace(c))
	  continue;

	// Modifier.
	if (c == '@')
	  {
	    frenchAccents = true;
	    continue;
	  }

	// Check for relation or reset operator.
	if (! (c == '<' || c == ';' || c == ',' || c == '=' || c == '&'))
	  throw new ParseException ("invalid character", index);

	++index;
	while (index < len)
	  {
	    if (! Character.isWhitespace(rules.charAt(index)))
	      break;
	    ++index;
	  }
	if (index == len)
	  throw new ParseException ("missing argument", index);

	int save = index;
	index = text_argument (rules, index, argument);
	if (argument.length() == 0)
	  throw new ParseException ("invalid character", save);
	String arg = argument.toString();
	int item_index = vec.indexOf(arg);
	if (c != '&')
	  {
	    // If the argument already appears in the vector, then we
	    // must remove it in order to re-order.
	    if (item_index != -1)
	      {
		vec.removeElementAt(item_index);
		if (insertion_index >= item_index)
		  --insertion_index;
	      }
	    RBCElement r = new RBCElement (arg, c);
	    vec.insertElementAt(r, insertion_index);
	    ++insertion_index;
	  }
	else
	  {
	    // Reset.
	    if (item_index == -1)
	      throw
		new ParseException ("argument to reset not previously seen",
				    save);
	    insertion_index = item_index + 1;
	  }

	// Ugly: in this case the resulting INDEX comes from
	// text_argument, which returns the index of the next
	// character we should examine.
	--index;
      }

    // Now construct a hash table that maps strings onto their
    // collation values.
    int primary = 0;
    int secondary = 0;
    int tertiary = 0;
    this.map = new Hashtable ();
    this.prefixes = new Hashtable ();
    Enumeration e = vec.elements();
    while (e.hasMoreElements())
      {
	RBCElement r = (RBCElement) e.nextElement();
	switch (r.relation)
	  {
	  case '<':
	    ++primary;
	    secondary = 0;
	    tertiary = 0;
	    break;
	  case ';':
	    ++secondary;
	    tertiary = 0;
	    break;
	  case ',':
	    ++tertiary;
	    break;
	  case '=':
	    break;
	  }
	// This must match CollationElementIterator.
	map.put(r.key, new Integer (primary << 16
				    | secondary << 8 | tertiary));

	// Make a map of all lookaheads we might need.
	for (int i = r.key.length() - 1; i >= 1; --i)
	  prefixes.put(r.key.substring(0, i), Boolean.TRUE);
      }
  }

  // True if we are using French-style accent ordering.
  private boolean frenchAccents;

  // It's easier to just save the rules than to try to recreate them.
  private String rules;

  // This maps strings onto collation values.
  private Hashtable map;
  // An entry in this hash means that more lookahead is required for
  // the prefix string.
  private Hashtable prefixes;
}