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/*
* (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
* (C) Copyright IBM Corp. 1996-1998 - All Rights Reserved
*
* The original version of this source code and documentation is copyrighted
* and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
* materials are provided under terms of a License Agreement between Taligent
* and Sun. This technology is protected by multiple US and International
* patents. This notice and attribution to Taligent may not be removed.
* Taligent is a registered trademark of Taligent, Inc.
*
*/
package java.text;
import java.text.Normalizer;
import java.util.Vector;
import java.util.Locale;
/**
* The <code>RuleBasedCollator</code> class is a concrete subclass of
* <code>Collator</code> that provides a simple, data-driven, table
* collator. With this class you can create a customized table-based
* <code>Collator</code>. <code>RuleBasedCollator</code> maps
* characters to sort keys.
*
* <p>
* <code>RuleBasedCollator</code> has the following restrictions
* for efficiency (other subclasses may be used for more complex languages) :
* <ol>
* <li>If a special collation rule controlled by a <modifier> is
specified it applies to the whole collator object.
* <li>All non-mentioned characters are at the end of the
* collation order.
* </ol>
*
* <p>
* The collation table is composed of a list of collation rules, where each
* rule is of one of three forms:
* <pre>
* <modifier>
* <relation> <text-argument>
* <reset> <text-argument>
* </pre>
* The definitions of the rule elements is as follows:
* <UL>
* <LI><strong>Text-Argument</strong>: A text-argument is any sequence of
* characters, excluding special characters (that is, common
* whitespace characters [0009-000D, 0020] and rule syntax characters
* [0021-002F, 003A-0040, 005B-0060, 007B-007E]). If those
* characters are desired, you can put them in single quotes
* (e.g. ampersand => '&'). Note that unquoted white space characters
* are ignored; e.g. <code>b c</code> is treated as <code>bc</code>.
* <LI><strong>Modifier</strong>: There are currently two modifiers that
* turn on special collation rules.
* <UL>
* <LI>'@' : Turns on backwards sorting of accents (secondary
* differences), as in French.
* <LI>'!' : Turns on Thai/Lao vowel-consonant swapping. If this
* rule is in force when a Thai vowel of the range
* \U0E40-\U0E44 precedes a Thai consonant of the range
* \U0E01-\U0E2E OR a Lao vowel of the range \U0EC0-\U0EC4
* precedes a Lao consonant of the range \U0E81-\U0EAE then
* the vowel is placed after the consonant for collation
* purposes.
* </UL>
* <p>'@' : Indicates that accents are sorted backwards, as in French.
* <LI><strong>Relation</strong>: The relations are the following:
* <UL>
* <LI>'<' : Greater, as a letter difference (primary)
* <LI>';' : Greater, as an accent difference (secondary)
* <LI>',' : Greater, as a case difference (tertiary)
* <LI>'=' : Equal
* </UL>
* <LI><strong>Reset</strong>: There is a single reset
* which is used primarily for contractions and expansions, but which
* can also be used to add a modification at the end of a set of rules.
* <p>'&' : Indicates that the next rule follows the position to where
* the reset text-argument would be sorted.
* </UL>
*
* <p>
* This sounds more complicated than it is in practice. For example, the
* following are equivalent ways of expressing the same thing:
* <blockquote>
* <pre>
* a < b < c
* a < b & b < c
* a < c & a < b
* </pre>
* </blockquote>
* Notice that the order is important, as the subsequent item goes immediately
* after the text-argument. The following are not equivalent:
* <blockquote>
* <pre>
* a < b & a < c
* a < c & a < b
* </pre>
* </blockquote>
* Either the text-argument must already be present in the sequence, or some
* initial substring of the text-argument must be present. (e.g. "a < b & ae <
* e" is valid since "a" is present in the sequence before "ae" is reset). In
* this latter case, "ae" is not entered and treated as a single character;
* instead, "e" is sorted as if it were expanded to two characters: "a"
* followed by an "e". This difference appears in natural languages: in
* traditional Spanish "ch" is treated as though it contracts to a single
* character (expressed as "c < ch < d"), while in traditional German
* a-umlaut is treated as though it expanded to two characters
* (expressed as "a,A < b,B ... &ae;\u00e3&AE;\u00c3").
* [\u00e3 and \u00c3 are, of course, the escape sequences for a-umlaut.]
* <p>
* <strong>Ignorable Characters</strong>
* <p>
* For ignorable characters, the first rule must start with a relation (the
* examples we have used above are really fragments; "a < b" really should be
* "< a < b"). If, however, the first relation is not "<", then all the all
* text-arguments up to the first "<" are ignorable. For example, ", - < a < b"
* makes "-" an ignorable character, as we saw earlier in the word
* "black-birds". In the samples for different languages, you see that most
* accents are ignorable.
*
* <p><strong>Normalization and Accents</strong>
* <p>
* <code>RuleBasedCollator</code> automatically processes its rule table to
* include both pre-composed and combining-character versions of
* accented characters. Even if the provided rule string contains only
* base characters and separate combining accent characters, the pre-composed
* accented characters matching all canonical combinations of characters from
* the rule string will be entered in the table.
* <p>
* This allows you to use a RuleBasedCollator to compare accented strings
* even when the collator is set to NO_DECOMPOSITION. There are two caveats,
* however. First, if the strings to be collated contain combining
* sequences that may not be in canonical order, you should set the collator to
* CANONICAL_DECOMPOSITION or FULL_DECOMPOSITION to enable sorting of
* combining sequences. Second, if the strings contain characters with
* compatibility decompositions (such as full-width and half-width forms),
* you must use FULL_DECOMPOSITION, since the rule tables only include
* canonical mappings.
*
* <p><strong>Errors</strong>
* <p>
* The following are errors:
* <UL>
* <LI>A text-argument contains unquoted punctuation symbols
* (e.g. "a < b-c < d").
* <LI>A relation or reset character not followed by a text-argument
* (e.g. "a < ,b").
* <LI>A reset where the text-argument (or an initial substring of the
* text-argument) is not already in the sequence.
* (e.g. "a < b & e < f")
* </UL>
* If you produce one of these errors, a <code>RuleBasedCollator</code> throws
* a <code>ParseException</code>.
*
* <p><strong>Examples</strong>
* <p>Simple: "< a < b < c < d"
* <p>Norwegian: "< a, A < b, B < c, C < d, D < e, E < f, F
* < g, G < h, H < i, I < j, J < k, K < l, L
* < m, M < n, N < o, O < p, P < q, Q < r, R
* < s, S < t, T < u, U < v, V < w, W < x, X
* < y, Y < z, Z
* < \u00E6, \u00C6
* < \u00F8, \u00D8
* < \u00E5 = a\u030A, \u00C5 = A\u030A;
* aa, AA"
*
* <p>
* To create a <code>RuleBasedCollator</code> object with specialized
* rules tailored to your needs, you construct the <code>RuleBasedCollator</code>
* with the rules contained in a <code>String</code> object. For example:
* <blockquote>
* <pre>
* String simple = "< a< b< c< d";
* RuleBasedCollator mySimple = new RuleBasedCollator(simple);
* </pre>
* </blockquote>
* Or:
* <blockquote>
* <pre>
* String Norwegian = "< a, A < b, B < c, C < d, D < e, E < f, F < g, G < h, H < i, I" +
* "< j, J < k, K < l, L < m, M < n, N < o, O < p, P < q, Q < r, R" +
* "< s, S < t, T < u, U < v, V < w, W < x, X < y, Y < z, Z" +
* "< \u00E6, \u00C6" + // Latin letter ae & AE
* "< \u00F8, \u00D8" + // Latin letter o & O with stroke
* "< \u00E5 = a\u030A," + // Latin letter a with ring above
* " \u00C5 = A\u030A;" + // Latin letter A with ring above
* " aa, AA";
* RuleBasedCollator myNorwegian = new RuleBasedCollator(Norwegian);
* </pre>
* </blockquote>
*
* <p>
* A new collation rules string can be created by concatenating rules
* strings. For example, the rules returned by {@link #getRules()} could
* be concatenated to combine multiple <code>RuleBasedCollator</code>s.
*
* <p>
* The following example demonstrates how to change the order of
* non-spacing accents,
* <blockquote>
* <pre>
* // old rule
* String oldRules = "=\u0301;\u0300;\u0302;\u0308" // main accents
* + ";\u0327;\u0303;\u0304;\u0305" // main accents
* + ";\u0306;\u0307;\u0309;\u030A" // main accents
* + ";\u030B;\u030C;\u030D;\u030E" // main accents
* + ";\u030F;\u0310;\u0311;\u0312" // main accents
* + "< a , A ; ae, AE ; \u00e6 , \u00c6"
* + "< b , B < c, C < e, E & C < d, D";
* // change the order of accent characters
* String addOn = "& \u0300 ; \u0308 ; \u0302";
* RuleBasedCollator myCollator = new RuleBasedCollator(oldRules + addOn);
* </pre>
* </blockquote>
*
* @see Collator
* @see CollationElementIterator
* @author Helena Shih, Laura Werner, Richard Gillam
*/
public class RuleBasedCollator extends Collator{
// IMPLEMENTATION NOTES: The implementation of the collation algorithm is
// divided across three classes: RuleBasedCollator, RBCollationTables, and
// CollationElementIterator. RuleBasedCollator contains the collator's
// transient state and includes the code that uses the other classes to
// implement comparison and sort-key building. RuleBasedCollator also
// contains the logic to handle French secondary accent sorting.
// A RuleBasedCollator has two CollationElementIterators. State doesn't
// need to be preserved in these objects between calls to compare() or
// getCollationKey(), but the objects persist anyway to avoid wasting extra
// creation time. compare() and getCollationKey() are synchronized to ensure
// thread safety with this scheme. The CollationElementIterator is responsible
// for generating collation elements from strings and returning one element at
// a time (sometimes there's a one-to-many or many-to-one mapping between
// characters and collation elements-- this class handles that).
// CollationElementIterator depends on RBCollationTables, which contains the
// collator's static state. RBCollationTables contains the actual data
// tables specifying the collation order of characters for a particular locale
// or use. It also contains the base logic that CollationElementIterator
// uses to map from characters to collation elements. A single RBCollationTables
// object is shared among all RuleBasedCollators for the same locale, and
// thus by all the CollationElementIterators they create.
/**
* RuleBasedCollator constructor. This takes the table rules and builds
* a collation table out of them. Please see RuleBasedCollator class
* description for more details on the collation rule syntax.
* @see java.util.Locale
* @param rules the collation rules to build the collation table from.
* @exception ParseException A format exception
* will be thrown if the build process of the rules fails. For
* example, build rule "a < ? < d" will cause the constructor to
* throw the ParseException because the '?' is not quoted.
*/
public RuleBasedCollator(String rules) throws ParseException {
this(rules, Collator.CANONICAL_DECOMPOSITION);
}
/**
* RuleBasedCollator constructor. This takes the table rules and builds
* a collation table out of them. Please see RuleBasedCollator class
* description for more details on the collation rule syntax.
* @see java.util.Locale
* @param rules the collation rules to build the collation table from.
* @param decomp the decomposition strength used to build the
* collation table and to perform comparisons.
* @exception ParseException A format exception
* will be thrown if the build process of the rules fails. For
* example, build rule "a < ? < d" will cause the constructor to
* throw the ParseException because the '?' is not quoted.
*/
RuleBasedCollator(String rules, int decomp) throws ParseException {
setStrength(Collator.TERTIARY);
setDecomposition(decomp);
tables = new RBCollationTables(rules, decomp);
}
/**
* "Copy constructor." Used in clone() for performance.
*/
private RuleBasedCollator(RuleBasedCollator that) {
setStrength(that.getStrength());
setDecomposition(that.getDecomposition());
tables = that.tables;
}
/**
* Gets the table-based rules for the collation object.
* @return returns the collation rules that the table collation object
* was created from.
*/
public String getRules()
{
return tables.getRules();
}
/**
* Returns a CollationElementIterator for the given String.
*
* @param source the string to be collated
* @return a {@code CollationElementIterator} object
* @see java.text.CollationElementIterator
*/
public CollationElementIterator getCollationElementIterator(String source) {
return new CollationElementIterator( source, this );
}
/**
* Returns a CollationElementIterator for the given CharacterIterator.
*
* @param source the character iterator to be collated
* @return a {@code CollationElementIterator} object
* @see java.text.CollationElementIterator
* @since 1.2
*/
public CollationElementIterator getCollationElementIterator(
CharacterIterator source) {
return new CollationElementIterator( source, this );
}
/**
* Compares the character data stored in two different strings based on the
* collation rules. Returns information about whether a string is less
* than, greater than or equal to another string in a language.
* This can be overriden in a subclass.
*
* @exception NullPointerException if <code>source</code> or <code>target</code> is null.
*/
public synchronized int compare(String source, String target)
{
if (source == null || target == null) {
throw new NullPointerException();
}
// The basic algorithm here is that we use CollationElementIterators
// to step through both the source and target strings. We compare each
// collation element in the source string against the corresponding one
// in the target, checking for differences.
//
// If a difference is found, we set <result> to LESS or GREATER to
// indicate whether the source string is less or greater than the target.
//
// However, it's not that simple. If we find a tertiary difference
// (e.g. 'A' vs. 'a') near the beginning of a string, it can be
// overridden by a primary difference (e.g. "A" vs. "B") later in
// the string. For example, "AA" < "aB", even though 'A' > 'a'.
//
// To keep track of this, we use strengthResult to keep track of the
// strength of the most significant difference that has been found
// so far. When we find a difference whose strength is greater than
// strengthResult, it overrides the last difference (if any) that
// was found.
int result = Collator.EQUAL;
if (sourceCursor == null) {
sourceCursor = getCollationElementIterator(source);
} else {
sourceCursor.setText(source);
}
if (targetCursor == null) {
targetCursor = getCollationElementIterator(target);
} else {
targetCursor.setText(target);
}
int sOrder = 0, tOrder = 0;
boolean initialCheckSecTer = getStrength() >= Collator.SECONDARY;
boolean checkSecTer = initialCheckSecTer;
boolean checkTertiary = getStrength() >= Collator.TERTIARY;
boolean gets = true, gett = true;
while(true) {
// Get the next collation element in each of the strings, unless
// we've been requested to skip it.
if (gets) sOrder = sourceCursor.next(); else gets = true;
if (gett) tOrder = targetCursor.next(); else gett = true;
// If we've hit the end of one of the strings, jump out of the loop
if ((sOrder == CollationElementIterator.NULLORDER)||
(tOrder == CollationElementIterator.NULLORDER))
break;
int pSOrder = CollationElementIterator.primaryOrder(sOrder);
int pTOrder = CollationElementIterator.primaryOrder(tOrder);
// If there's no difference at this position, we can skip it
if (sOrder == tOrder) {
if (tables.isFrenchSec() && pSOrder != 0) {
if (!checkSecTer) {
// in french, a secondary difference more to the right is stronger,
// so accents have to be checked with each base element
checkSecTer = initialCheckSecTer;
// but tertiary differences are less important than the first
// secondary difference, so checking tertiary remains disabled
checkTertiary = false;
}
}
continue;
}
// Compare primary differences first.
if ( pSOrder != pTOrder )
{
if (sOrder == 0) {
// The entire source element is ignorable.
// Skip to the next source element, but don't fetch another target element.
gett = false;
continue;
}
if (tOrder == 0) {
gets = false;
continue;
}
// The source and target elements aren't ignorable, but it's still possible
// for the primary component of one of the elements to be ignorable....
if (pSOrder == 0) // primary order in source is ignorable
{
// The source's primary is ignorable, but the target's isn't. We treat ignorables
// as a secondary difference, so remember that we found one.
if (checkSecTer) {
result = Collator.GREATER; // (strength is SECONDARY)
checkSecTer = false;
}
// Skip to the next source element, but don't fetch another target element.
gett = false;
}
else if (pTOrder == 0)
{
// record differences - see the comment above.
if (checkSecTer) {
result = Collator.LESS; // (strength is SECONDARY)
checkSecTer = false;
}
// Skip to the next source element, but don't fetch another target element.
gets = false;
} else {
// Neither of the orders is ignorable, and we already know that the primary
// orders are different because of the (pSOrder != pTOrder) test above.
// Record the difference and stop the comparison.
if (pSOrder < pTOrder) {
return Collator.LESS; // (strength is PRIMARY)
} else {
return Collator.GREATER; // (strength is PRIMARY)
}
}
} else { // else of if ( pSOrder != pTOrder )
// primary order is the same, but complete order is different. So there
// are no base elements at this point, only ignorables (Since the strings are
// normalized)
if (checkSecTer) {
// a secondary or tertiary difference may still matter
short secSOrder = CollationElementIterator.secondaryOrder(sOrder);
short secTOrder = CollationElementIterator.secondaryOrder(tOrder);
if (secSOrder != secTOrder) {
// there is a secondary difference
result = (secSOrder < secTOrder) ? Collator.LESS : Collator.GREATER;
// (strength is SECONDARY)
checkSecTer = false;
// (even in french, only the first secondary difference within
// a base character matters)
} else {
if (checkTertiary) {
// a tertiary difference may still matter
short terSOrder = CollationElementIterator.tertiaryOrder(sOrder);
short terTOrder = CollationElementIterator.tertiaryOrder(tOrder);
if (terSOrder != terTOrder) {
// there is a tertiary difference
result = (terSOrder < terTOrder) ? Collator.LESS : Collator.GREATER;
// (strength is TERTIARY)
checkTertiary = false;
}
}
}
} // if (checkSecTer)
} // if ( pSOrder != pTOrder )
} // while()
if (sOrder != CollationElementIterator.NULLORDER) {
// (tOrder must be CollationElementIterator::NULLORDER,
// since this point is only reached when sOrder or tOrder is NULLORDER.)
// The source string has more elements, but the target string hasn't.
do {
if (CollationElementIterator.primaryOrder(sOrder) != 0) {
// We found an additional non-ignorable base character in the source string.
// This is a primary difference, so the source is greater
return Collator.GREATER; // (strength is PRIMARY)
}
else if (CollationElementIterator.secondaryOrder(sOrder) != 0) {
// Additional secondary elements mean the source string is greater
if (checkSecTer) {
result = Collator.GREATER; // (strength is SECONDARY)
checkSecTer = false;
}
}
} while ((sOrder = sourceCursor.next()) != CollationElementIterator.NULLORDER);
}
else if (tOrder != CollationElementIterator.NULLORDER) {
// The target string has more elements, but the source string hasn't.
do {
if (CollationElementIterator.primaryOrder(tOrder) != 0)
// We found an additional non-ignorable base character in the target string.
// This is a primary difference, so the source is less
return Collator.LESS; // (strength is PRIMARY)
else if (CollationElementIterator.secondaryOrder(tOrder) != 0) {
// Additional secondary elements in the target mean the source string is less
if (checkSecTer) {
result = Collator.LESS; // (strength is SECONDARY)
checkSecTer = false;
}
}
} while ((tOrder = targetCursor.next()) != CollationElementIterator.NULLORDER);
}
// For IDENTICAL comparisons, we use a bitwise character comparison
// as a tiebreaker if all else is equal
if (result == 0 && getStrength() == IDENTICAL) {
int mode = getDecomposition();
Normalizer.Form form;
if (mode == CANONICAL_DECOMPOSITION) {
form = Normalizer.Form.NFD;
} else if (mode == FULL_DECOMPOSITION) {
form = Normalizer.Form.NFKD;
} else {
return source.compareTo(target);
}
String sourceDecomposition = Normalizer.normalize(source, form);
String targetDecomposition = Normalizer.normalize(target, form);
return sourceDecomposition.compareTo(targetDecomposition);
}
return result;
}
/**
* Transforms the string into a series of characters that can be compared
* with CollationKey.compareTo. This overrides java.text.Collator.getCollationKey.
* It can be overriden in a subclass.
*/
public synchronized CollationKey getCollationKey(String source)
{
//
// The basic algorithm here is to find all of the collation elements for each
// character in the source string, convert them to a char representation,
// and put them into the collation key. But it's trickier than that.
// Each collation element in a string has three components: primary (A vs B),
// secondary (A vs A-acute), and tertiary (A' vs a); and a primary difference
// at the end of a string takes precedence over a secondary or tertiary
// difference earlier in the string.
//
// To account for this, we put all of the primary orders at the beginning of the
// string, followed by the secondary and tertiary orders, separated by nulls.
//
// Here's a hypothetical example, with the collation element represented as
// a three-digit number, one digit for primary, one for secondary, etc.
//
// String: A a B \u00e9 <--(e-acute)
// Collation Elements: 101 100 201 510
//
// Collation Key: 1125<null>0001<null>1010
//
// To make things even trickier, secondary differences (accent marks) are compared
// starting at the *end* of the string in languages with French secondary ordering.
// But when comparing the accent marks on a single base character, they are compared
// from the beginning. To handle this, we reverse all of the accents that belong
// to each base character, then we reverse the entire string of secondary orderings
// at the end. Taking the same example above, a French collator might return
// this instead:
//
// Collation Key: 1125<null>1000<null>1010
//
if (source == null)
return null;
if (primResult == null) {
primResult = new StringBuffer();
secResult = new StringBuffer();
terResult = new StringBuffer();
} else {
primResult.setLength(0);
secResult.setLength(0);
terResult.setLength(0);
}
int order = 0;
boolean compareSec = (getStrength() >= Collator.SECONDARY);
boolean compareTer = (getStrength() >= Collator.TERTIARY);
int secOrder = CollationElementIterator.NULLORDER;
int terOrder = CollationElementIterator.NULLORDER;
int preSecIgnore = 0;
if (sourceCursor == null) {
sourceCursor = getCollationElementIterator(source);
} else {
sourceCursor.setText(source);
}
// walk through each character
while ((order = sourceCursor.next()) !=
CollationElementIterator.NULLORDER)
{
secOrder = CollationElementIterator.secondaryOrder(order);
terOrder = CollationElementIterator.tertiaryOrder(order);
if (!CollationElementIterator.isIgnorable(order))
{
primResult.append((char) (CollationElementIterator.primaryOrder(order)
+ COLLATIONKEYOFFSET));
if (compareSec) {
//
// accumulate all of the ignorable/secondary characters attached
// to a given base character
//
if (tables.isFrenchSec() && preSecIgnore < secResult.length()) {
//
// We're doing reversed secondary ordering and we've hit a base
// (non-ignorable) character. Reverse any secondary orderings
// that applied to the last base character. (see block comment above.)
//
RBCollationTables.reverse(secResult, preSecIgnore, secResult.length());
}
// Remember where we are in the secondary orderings - this is how far
// back to go if we need to reverse them later.
secResult.append((char)(secOrder+ COLLATIONKEYOFFSET));
preSecIgnore = secResult.length();
}
if (compareTer) {
terResult.append((char)(terOrder+ COLLATIONKEYOFFSET));
}
}
else
{
if (compareSec && secOrder != 0)
secResult.append((char)
(secOrder + tables.getMaxSecOrder() + COLLATIONKEYOFFSET));
if (compareTer && terOrder != 0)
terResult.append((char)
(terOrder + tables.getMaxTerOrder() + COLLATIONKEYOFFSET));
}
}
if (tables.isFrenchSec())
{
if (preSecIgnore < secResult.length()) {
// If we've accumulated any secondary characters after the last base character,
// reverse them.
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