/*
 * Copyright (c) 2005, 2020, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 *******************************************************************************
 * Copyright (C) 1996-2015, International Business Machines Corporation and
 * others. All Rights Reserved.
 *******************************************************************************
 */
package jdk_internal.icu.text;

import java.text.ParsePosition;
import java.util.ArrayList;
import java.util.TreeSet;

import jdk_internal.icu.impl.BMPSet;
import jdk_internal.icu.impl.UCharacterProperty;
import jdk_internal.icu.impl.UnicodeSetStringSpan;
import jdk_internal.icu.impl.Utility;
import jdk_internal.icu.lang.UCharacter;
import jdk_internal.icu.util.OutputInt;
import jdk_internal.icu.util.VersionInfo;

/**
 * A mutable set of Unicode characters and multicharacter strings. Objects of
 * this class represent <em>character classes</em> used in regular expressions.
 * A character specifies a subset of Unicode code points. Legal code points are
 * U+0000 to U+10FFFF, inclusive.
 *
 * Note: method freeze() will not only make the set immutable, but also makes
 * important methods much higher performance: contains(c), containsNone(...),
 * span(...), spanBack(...) etc. After the object is frozen, any subsequent call
 * that wants to change the object will throw UnsupportedOperationException.
 *
 * <p>
 * The UnicodeSet class is not designed to be subclassed.
 *
 * <p>
 * <code>UnicodeSet</code> supports two APIs. The first is the <em>operand</em>
 * API that allows the caller to modify the value of a <code>UnicodeSet</code>
 * object. It conforms to Java 2's <code>java.util.Set</code> interface,
 * although <code>UnicodeSet</code> does not actually implement that interface.
 * All methods of <code>Set</code> are supported, with the modification that
 * they take a character range or single character instead of an
 * <code>Object</code>, and they take a <code>UnicodeSet</code> instead of a
 * <code>Collection</code>. The operand API may be thought of in terms of
 * boolean logic: a boolean OR is implemented by <code>add</code>, a boolean AND
 * is implemented by <code>retain</code>, a boolean XOR is implemented by
 * <code>complement</code> taking an argument, and a boolean NOT is implemented
 * by <code>complement</code> with no argument. In terms of traditional set
 * theory function names, <code>add</code> is a union, <code>retain</code> is an
 * intersection, <code>remove</code> is an asymmetric difference, and
 * <code>complement</code> with no argument is a set complement with respect to
 * the superset range <code>MIN_VALUE-MAX_VALUE</code>
 *
 * <p>
 * The second API is the <code>applyPattern()</code>/<code>toPattern()</code>
 * API from the <code>java.text.Format</code>-derived classes. Unlike the
 * methods that add characters, add categories, and control the logic of the
 * set, the method <code>applyPattern()</code> sets all attributes of a
 * <code>UnicodeSet</code> at once, based on a string pattern.
 *
 * <p>
 * <b>Pattern syntax</b>
 * </p>
 *
 * Patterns are accepted by the constructors and the <code>applyPattern()</code>
 * methods and returned by the <code>toPattern()</code> method. These patterns
 * follow a syntax similar to that employed by version 8 regular expression
 * character classes. Here are some simple examples:
 *
 * <blockquote>
 * <table>
 * <tr align="top">
 * <td nowrap valign="top" align="left"><code>[]</code></td>
 * <td valign="top">No characters</td>
 * </tr>
 * <tr align="top">
 * <td nowrap valign="top" align="left"><code>[a]</code></td>
 * <td valign="top">The character 'a'</td>
 * </tr>
 * <tr align="top">
 * <td nowrap valign="top" align="left"><code>[ae]</code></td>
 * <td valign="top">The characters 'a' and 'e'</td>
 * </tr>
 * <tr>
 * <td nowrap valign="top" align="left"><code>[a-e]</code></td>
 * <td valign="top">The characters 'a' through 'e' inclusive, in Unicode code
 * point order</td>
 * </tr>
 * <tr>
 * <td nowrap valign="top" align="left"><code>[\\u4E01]</code></td>
 * <td valign="top">The character U+4E01</td>
 * </tr>
 * <tr>
 * <td nowrap valign="top" align="left"><code>[a{ab}{ac}]</code></td>
 * <td valign="top">The character 'a' and the multicharacter strings "ab" and
 * "ac"</td>
 * </tr>
 * <tr>
 * <td nowrap valign="top" align="left"><code>[\p{Lu}]</code></td>
 * <td valign="top">All characters in the general category Uppercase Letter</td>
 * </tr>
 * </table>
 * </blockquote>
 *
 * Any character may be preceded by a backslash in order to remove any special
 * meaning. White space characters, as defined by the Unicode
 * Pattern_White_Space property, are ignored, unless they are escaped.
 *
 * <p>
 * Property patterns specify a set of characters having a certain property as
 * defined by the Unicode standard. Both the POSIX-like "[:Lu:]" and the
 * Perl-like syntax "\p{Lu}" are recognized. For a complete list of supported
 * property patterns, see the User's Guide for UnicodeSet at
 * <a href="http://www.icu-project.org/userguide/unicodeSet.html">
 * http://www.icu-project.org/userguide/unicodeSet.html</a>. Actual
 * determination of property data is defined by the underlying Unicode database
 * as implemented by UCharacter.
 *
 * <p>
 * Patterns specify individual characters, ranges of characters, and Unicode
 * property sets. When elements are concatenated, they specify their union. To
 * complement a set, place a '^' immediately after the opening '['. Property
 * patterns are inverted by modifying their delimiters; "[:^foo]" and "\P{foo}".
 * In any other location, '^' has no special meaning.
 *
 * <p>
 * Ranges are indicated by placing two a '-' between two characters, as in
 * "a-z". This specifies the range of all characters from the left to the right,
 * in Unicode order. If the left character is greater than or equal to the right
 * character it is a syntax error. If a '-' occurs as the first character after
 * the opening '[' or '[^', or if it occurs as the last character before the
 * closing ']', then it is taken as a literal. Thus "[a\\-b]", "[-ab]", and
 * "[ab-]" all indicate the same set of three characters, 'a', 'b', and '-'.
 *
 * <p>
 * Sets may be intersected using the {@literal '&'} operator or the asymmetric
 * set difference may be taken using the '-' operator, for example,
 * "{@code [[:L:]&[\\u0000-\\u0FFF]]}" indicates the set of all Unicode letters
 * with values less than 4096. Operators ({@literal '&'} and '|') have equal
 * precedence and bind left-to-right. Thus "[[:L:]-[a-z]-[\\u0100-\\u01FF]]" is
 * equivalent to "[[[:L:]-[a-z]]-[\\u0100-\\u01FF]]". This only really matters
 * for difference; intersection is commutative.
 *
 * <table>
 * <tr valign=top>
 * <td nowrap><code>[a]</code>
 * <td>The set containing 'a'
 * <tr valign=top>
 * <td nowrap><code>[a-z]</code>
 * <td>The set containing 'a' through 'z' and all letters in between, in Unicode
 * order
 * <tr valign=top>
 * <td nowrap><code>[^a-z]</code>
 * <td>The set containing all characters but 'a' through 'z', that is, U+0000
 * through 'a'-1 and 'z'+1 through U+10FFFF
 * <tr valign=top>
 * <td nowrap><code>[[<em>pat1</em>][<em>pat2</em>]]</code>
 * <td>The union of sets specified by <em>pat1</em> and <em>pat2</em>
 * <tr valign=top>
 * <td nowrap><code>[[<em>pat1</em>]&amp;[<em>pat2</em>]]</code>
 * <td>The intersection of sets specified by <em>pat1</em> and <em>pat2</em>
 * <tr valign=top>
 * <td nowrap><code>[[<em>pat1</em>]-[<em>pat2</em>]]</code>
 * <td>The asymmetric difference of sets specified by <em>pat1</em> and
 * <em>pat2</em>
 * <tr valign=top>
 * <td nowrap><code>[:Lu:] or \p{Lu}</code>
 * <td>The set of characters having the specified Unicode property; in this
 * case, Unicode uppercase letters
 * <tr valign=top>
 * <td nowrap><code>[:^Lu:] or \P{Lu}</code>
 * <td>The set of characters <em>not</em> having the given Unicode property
 * </table>
 *
 * <p>
 * <b>Warning</b>: you cannot add an empty string ("") to a UnicodeSet.
 * </p>
 *
 * <p>
 * <b>Formal syntax</b>
 * </p>
 *
 * <blockquote>
 * <table>
 * <tr align="top">
 * <td nowrap valign="top" align="right"><code>pattern :=&nbsp; </code></td>
 * <td valign="top"><code>('[' '^'? item* ']') |
 *       property</code></td>
 * </tr>
 * <tr align="top">
 * <td nowrap valign="top" align="right"><code>item :=&nbsp; </code></td>
 * <td valign="top"><code>char | (char '-' char) | pattern-expr<br>
 *       </code></td>
 * </tr>
 * <tr align="top">
 * <td nowrap valign="top"
 * align="right"><code>pattern-expr :=&nbsp; </code></td>
 * <td valign="top"><code>pattern | pattern-expr pattern |
 *       pattern-expr op pattern<br>
 *       </code></td>
 * </tr>
 * <tr align="top">
 * <td nowrap valign="top" align="right"><code>op :=&nbsp; </code></td>
 * <td valign="top"><code>'&amp;' | '-'<br>
 *       </code></td>
 * </tr>
 * <tr align="top">
 * <td nowrap valign="top" align="right"><code>special :=&nbsp; </code></td>
 * <td valign="top"><code>'[' | ']' | '-'<br>
 *       </code></td>
 * </tr>
 * <tr align="top">
 * <td nowrap valign="top" align="right"><code>char :=&nbsp; </code></td>
 * <td valign="top"><em>any character that is not</em><code> special<br>
 *       | ('\\' </code><em>any character</em><code>)<br>
 *       | ('&#92;u' hex hex hex hex)<br>
 *       </code></td>
 * </tr>
 * <tr align="top">
 * <td nowrap valign="top" align="right"><code>hex :=&nbsp; </code></td>
 * <td valign="top"><em>any character for which
 * </em><code>Character.digit(c, 16)</code><em> returns a non-negative
 * result</em></td>
 * </tr>
 * <tr>
 * <td nowrap valign="top" align="right"><code>property :=&nbsp; </code></td>
 * <td valign="top"><em>a Unicode property set pattern</em></td>
 * </tr>
 * </table>
 * <br>
 * <table border="1">
 * <tr>
 * <td>Legend:
 * <table>
 * <tr>
 * <td nowrap valign="top"><code>a := b</code></td>
 * <td width="20" valign="top">&nbsp;</td>
 * <td valign="top"><code>a</code> may be replaced by <code>b</code></td>
 * </tr>
 * <tr>
 * <td nowrap valign="top"><code>a?</code></td>
 * <td valign="top"></td>
 * <td valign="top">zero or one instance of <code>a</code><br>
 * </td>
 * </tr>
 * <tr>
 * <td nowrap valign="top"><code>a*</code></td>
 * <td valign="top"></td>
 * <td valign="top">one or more instances of <code>a</code><br>
 * </td>
 * </tr>
 * <tr>
 * <td nowrap valign="top"><code>a | b</code></td>
 * <td valign="top"></td>
 * <td valign="top">either <code>a</code> or <code>b</code><br>
 * </td>
 * </tr>
 * <tr>
 * <td nowrap valign="top"><code>'a'</code></td>
 * <td valign="top"></td>
 * <td valign="top">the literal string between the quotes</td>
 * </tr>
 * </table>
 * </td>
 * </tr>
 * </table>
 * </blockquote>
 * <p>
 * To iterate over contents of UnicodeSet, the following are available:
 * <ul>
 * <li>{@link #ranges()} to iterate through the ranges</li>
 * <li>{@link #strings()} to iterate through the strings</li>
 * <li>{@link #iterator()} to iterate through the entire contents in a single
 * loop. That method is, however, not particularly efficient, since it "boxes"
 * each code point into a String.
 * </ul>
 * All of the above can be used in <b>for</b> loops. The
 * {@link com.ibm.icu.text.UnicodeSetIterator UnicodeSetIterator} can also be
 * used, but not in <b>for</b> loops.
 * <p>
 * To replace, count elements, or delete spans, see
 * {@link com.ibm.icu.text.UnicodeSetSpanner UnicodeSetSpanner}.
 *
 * @author Alan Liu
 * @stable ICU 2.0
 */
public class UnicodeSet {

	private static interface Filter {
		boolean contains(int codePoint);
	}

	/**
	 * Argument values for whether span() and similar functions continue while the
	 * current character is contained vs. not contained in the set.
	 * <p>
	 * The functionality is straightforward for sets with only single code points,
	 * without strings (which is the common case):
	 * <ul>
	 * <li>CONTAINED and SIMPLE work the same.
	 * <li>CONTAINED and SIMPLE are inverses of NOT_CONTAINED.
	 * <li>span() and spanBack() partition any string the same way when alternating
	 * between span(NOT_CONTAINED) and span(either "contained" condition).
	 * <li>Using a complemented (inverted) set and the opposite span conditions
	 * yields the same results.
	 * </ul>
	 * When a set contains multi-code point strings, then these statements may not
	 * be true, depending on the strings in the set (for example, whether they
	 * overlap with each other) and the string that is processed. For a set with
	 * strings:
	 * <ul>
	 * <li>The complement of the set contains the opposite set of code points, but
	 * the same set of strings. Therefore, complementing both the set and the span
	 * conditions may yield different results.
	 * <li>When starting spans at different positions in a string (span(s, ...) vs.
	 * span(s+1, ...)) the ends of the spans may be different because a set string
	 * may start before the later position.
	 * <li>span(SIMPLE) may be shorter than span(CONTAINED) because it will not
	 * recursively try all possible paths. For example, with a set which contains
	 * the three strings "xy", "xya" and "ax", span("xyax", CONTAINED) will return 4
	 * but span("xyax", SIMPLE) will return 3. span(SIMPLE) will never be longer
	 * than span(CONTAINED).
	 * <li>With either "contained" condition, span() and spanBack() may partition a
	 * string in different ways. For example, with a set which contains the two
	 * strings "ab" and "ba", and when processing the string "aba", span() will
	 * yield contained/not-contained boundaries of { 0, 2, 3 } while spanBack() will
	 * yield boundaries of { 0, 1, 3 }.
	 * </ul>
	 * Note: If it is important to get the same boundaries whether iterating forward
	 * or backward through a string, then either only span() should be used and the
	 * boundaries cached for backward operation, or an ICU BreakIterator could be
	 * used.
	 * <p>
	 * Note: Unpaired surrogates are treated like surrogate code points. Similarly,
	 * set strings match only on code point boundaries, never in the middle of a
	 * surrogate pair.
	 *
	 * @stable ICU 4.4
	 */
	public enum SpanCondition {
		/**
		 * Continues a span() while there is no set element at the current position.
		 * Increments by one code point at a time. Stops before the first set element
		 * (character or string). (For code points only, this is like while
		 * contains(current)==false).
		 * <p>
		 * When span() returns, the substring between where it started and the position
		 * it returned consists only of characters that are not in the set, and none of
		 * its strings overlap with the span.
		 *
		 * @stable ICU 4.4
		 */
		NOT_CONTAINED,

		/**
		 * Spans the longest substring that is a concatenation of set elements
		 * (characters or strings). (For characters only, this is like while
		 * contains(current)==true).
		 * <p>
		 * When span() returns, the substring between where it started and the position
		 * it returned consists only of set elements (characters or strings) that are in
		 * the set.
		 * <p>
		 * If a set contains strings, then the span will be the longest substring for
		 * which there exists at least one non-overlapping concatenation of set elements
		 * (characters or strings). This is equivalent to a POSIX regular expression for
		 * <code>(OR of each set element)*</code>. (Java/ICU/Perl regex stops at the
		 * first match of an OR.)
		 *
		 * @stable ICU 4.4
		 */
		CONTAINED,

		/**
		 * Continues a span() while there is a set element at the current position.
		 * Increments by the longest matching element at each position. (For characters
		 * only, this is like while contains(current)==true).
		 * <p>
		 * When span() returns, the substring between where it started and the position
		 * it returned consists only of set elements (characters or strings) that are in
		 * the set.
		 * <p>
		 * If a set only contains single characters, then this is the same as CONTAINED.
		 * <p>
		 * If a set contains strings, then the span will be the longest substring with a
		 * match at each position with the longest single set element (character or
		 * string).
		 * <p>
		 * Use this span condition together with other longest-match algorithms, such as
		 * ICU converters (ucnv_getUnicodeSet()).
		 *
		 * @stable ICU 4.4
		 */
		SIMPLE,
	}

	private static class VersionFilter implements Filter {
		VersionInfo version;

		VersionFilter(VersionInfo version) {
			this.version = version;
		}

		@Override
		public boolean contains(int ch) {
			VersionInfo v = UCharacter.getAge(ch);
			// Reference comparison ok; VersionInfo caches and reuses
			// unique objects.
			return v != NO_VERSION && v.compareTo(version) <= 0;
		}
	}

	private static final int LOW = 0x000000; // LOW <= all valid values. ZERO for codepoints

	private static final int HIGH = 0x110000; // HIGH > all valid values. 10000 for code units.
	// 110000 for codepoints
	/**
	 * Minimum value that can be stored in a UnicodeSet.
	 *
	 * @stable ICU 2.0
	 */
	public static final int MIN_VALUE = LOW;
	/**
	 * Maximum value that can be stored in a UnicodeSet.
	 *
	 * @stable ICU 2.0
	 */
	public static final int MAX_VALUE = HIGH - 1;
	/**
	 * The pattern representation of this set. This may not be the most economical
	 * pattern. It is the pattern supplied to applyPattern(), with variables
	 * substituted and whitespace removed. For sets constructed without
	 * applyPattern(), or modified using the non-pattern API, this string will be
	 * null, indicating that toPattern() must generate a pattern representation from
	 * the inversion list.
	 */

	private static final int START_EXTRA = 16; // initial storage. Must be >= 0

	private static final int GROW_EXTRA = START_EXTRA; // extra amount for growth. Must be >= 0

	private static UnicodeSet INCLUSION = null;
	private static final VersionInfo NO_VERSION = VersionInfo.getInstance(0, 0, 0, 0);

	private static synchronized UnicodeSet getInclusions(int src) {
		if (src != UCharacterProperty.SRC_PROPSVEC) {
			throw new IllegalStateException("UnicodeSet.getInclusions(unknown src " + src + ")");
		}

		if (INCLUSION == null) {
			UnicodeSet incl = new UnicodeSet();
			UCharacterProperty.INSTANCE.upropsvec_addPropertyStarts(incl);
			INCLUSION = incl;
		}
		return INCLUSION;
	}

	/**
	 * Utility for getting code point from single code point CharSequence. See the
	 * public UTF16.getSingleCodePoint()
	 *
	 * @return a code point IF the string consists of a single one. otherwise
	 *         returns -1.
	 * @param s to test
	 */
	private static int getSingleCP(CharSequence s) {
		if (s.length() < 1) {
			throw new IllegalArgumentException("Can't use zero-length strings in UnicodeSet");
		}
		if (s.length() > 2)
			return -1;
		if (s.length() == 1)
			return s.charAt(0);

		// at this point, len = 2
		int cp = UTF16.charAt(s, 0);
		if (cp > 0xFFFF) { // is surrogate pair
			return cp;
		}
		return -1;
	}

	private static final int max(int a, int b) {
		return (a > b) ? a : b;
	}

	// ----------------------------------------------------------------
	// Public API
	// ----------------------------------------------------------------

	private int len; // length used; list may be longer to minimize reallocs

	private int[] list; // MUST be terminated with HIGH

	private int[] rangeList; // internal buffer

	private int[] buffer; // internal buffer

	// NOTE: normally the field should be of type SortedSet; but that is missing a
	// public clone!!
	// is not private so that UnicodeSetIterator can get access
	TreeSet<String> strings = new TreeSet<String>();

	private volatile BMPSet bmpSet; // The set is frozen if bmpSet or stringSpan is not null.

	private volatile UnicodeSetStringSpan stringSpan;

	/**
	 * Constructs an empty set.
	 *
	 * @stable ICU 2.0
	 */
	private UnicodeSet() {
		list = new int[1 + START_EXTRA];
		list[len++] = HIGH;
	}

	/**
	 * Constructs a set containing the given range. If <code>end >
	 * start</code> then an empty set is created.
	 *
	 * @param start first character, inclusive, of range
	 * @param end   last character, inclusive, of range
	 * @stable ICU 2.0
	 */
	public UnicodeSet(int start, int end) {
		this();
		complement(start, end);
	}

	/**
	 * Constructs a set from the given pattern. See the class description for the
	 * syntax of the pattern language. Whitespace is ignored.
	 *
	 * @param pattern a string specifying what characters are in the set
	 * @exception java.lang.IllegalArgumentException if the pattern contains a
	 *                                               syntax error.
	 * @stable ICU 2.0
	 */
	public UnicodeSet(String pattern) {
		this();
		applyPattern(pattern, null);
	}

	/**
	 * Constructs a copy of an existing set.
	 *
	 * @stable ICU 2.0
	 */
	private UnicodeSet(UnicodeSet other) {
		set(other);
	}

	/**
	 * Adds the specified multicharacter to this set if it is not already present.
	 * If this set already contains the multicharacter, the call leaves this set
	 * unchanged. Thus {@code "ch" => {"ch"}} <br>
	 * <b>Warning: you cannot add an empty string ("") to a UnicodeSet.</b>
	 *
	 * @param s the source string
	 * @return this object, for chaining
	 * @stable ICU 2.0
	 */
	public final UnicodeSet add(CharSequence s) {
		checkFrozen();
		int cp = getSingleCP(s);
		if (cp < 0) {
			strings.add(s.toString());
		} else {
			add_unchecked(cp, cp);
		}
		return this;
	}

	/**
	 * Adds the specified character to this set if it is not already present. If
	 * this set already contains the specified character, the call leaves this set
	 * unchanged.
	 *
	 * @stable ICU 2.0
	 */
	public final UnicodeSet add(int c) {
		checkFrozen();
		return add_unchecked(c);
	}

	private UnicodeSet add(int[] other, int otherLen, int polarity) {
		ensureBufferCapacity(len + otherLen);
		int i = 0, j = 0, k = 0;
		int a = list[i++];
		int b = other[j++];
		// change from xor is that we have to check overlapping pairs
		// polarity bit 1 means a is second, bit 2 means b is.
		main: while (true) {
			switch (polarity) {
			case 0: // both first; take lower if unequal
				if (a < b) { // take a
					// Back up over overlapping ranges in buffer[]
					if (k > 0 && a <= buffer[k - 1]) {
						// Pick latter end value in buffer[] vs. list[]
						a = max(list[i], buffer[--k]);
					} else {
						// No overlap
						buffer[k++] = a;
						a = list[i];
					}
					i++; // Common if/else code factored out
					polarity ^= 1;
				} else if (b < a) { // take b
					if (k > 0 && b <= buffer[k - 1]) {
						b = max(other[j], buffer[--k]);
					} else {
						buffer[k++] = b;
						b = other[j];
					}
					j++;
					polarity ^= 2;
				} else { // a == b, take a, drop b
					if (a == HIGH)
						break main;
					// This is symmetrical; it doesn't matter if
					// we backtrack with a or b. - liu
					if (k > 0 && a <= buffer[k - 1]) {
						a = max(list[i], buffer[--k]);
					} else {
						// No overlap
						buffer[k++] = a;
						a = list[i];
					}
					i++;
					polarity ^= 1;
					b = other[j++];
					polarity ^= 2;
				}
				break;
			case 3: // both second; take higher if unequal, and drop other
				if (b <= a) { // take a
					if (a == HIGH)
						break main;
					buffer[k++] = a;
				} else { // take b
					if (b == HIGH)
						break main;
					buffer[k++] = b;
				}
				a = list[i++];
				polarity ^= 1; // factored common code
				b = other[j++];
				polarity ^= 2;
				break;
			case 1: // a second, b first; if b < a, overlap
				if (a < b) { // no overlap, take a
					buffer[k++] = a;
					a = list[i++];
					polarity ^= 1;
				} else if (b < a) { // OVERLAP, drop b
					b = other[j++];
					polarity ^= 2;
				} else { // a == b, drop both!
					if (a == HIGH)
						break main;
					a = list[i++];
					polarity ^= 1;
					b = other[j++];
					polarity ^= 2;
				}
				break;
			case 2: // a first, b second; if a < b, overlap
				if (b < a) { // no overlap, take b
					buffer[k++] = b;
					b = other[j++];
					polarity ^= 2;
				} else if (a < b) { // OVERLAP, drop a
					a = list[i++];
					polarity ^= 1;
				} else { // a == b, drop both!
					if (a == HIGH)
						break main;
					a = list[i++];
					polarity ^= 1;
					b = other[j++];
					polarity ^= 2;
				}
				break;
			}
		}
		buffer[k++] = HIGH; // terminate
		len = k;
		// swap list and buffer
		int[] temp = list;
		list = buffer;
		buffer = temp;
		return this;
	}

	// for internal use only, after checkFrozen has been called
	private final UnicodeSet add_unchecked(int c) {
		if (c < MIN_VALUE || c > MAX_VALUE) {
			throw new IllegalArgumentException("Invalid code point U+" + Utility.hex(c, 6));
		}

		// find smallest i such that c < list[i]
		// if odd, then it is IN the set
		// if even, then it is OUT of the set
		int i = findCodePoint(c);

		// already in set?
		if ((i & 1) != 0)
			return this;

		// HIGH is 0x110000
		// assert(list[len-1] == HIGH);

		// empty = [HIGH]
		// [start_0, limit_0, start_1, limit_1, HIGH]

		// [..., start_k-1, limit_k-1, start_k, limit_k, ..., HIGH]
		// ^
		// list[i]

		// i == 0 means c is before the first range

		if (c == list[i] - 1) {
			// c is before start of next range
			list[i] = c;
			// if we touched the HIGH mark, then add a new one
			if (c == MAX_VALUE) {
				ensureCapacity(len + 1);
				list[len++] = HIGH;
			}
			if (i > 0 && c == list[i - 1]) {
				// collapse adjacent ranges

				// [..., start_k-1, c, c, limit_k, ..., HIGH]
				// ^
				// list[i]
				System.arraycopy(list, i + 1, list, i - 1, len - i - 1);
				len -= 2;
			}
		}

		else if (i > 0 && c == list[i - 1]) {
			// c is after end of prior range
			list[i - 1]++;
			// no need to chcek for collapse here
		}

		else {
			// At this point we know the new char is not adjacent to
			// any existing ranges, and it is not 10FFFF.

			// [..., start_k-1, limit_k-1, start_k, limit_k, ..., HIGH]
			// ^
			// list[i]

			// [..., start_k-1, limit_k-1, c, c+1, start_k, limit_k, ..., HIGH]
			// ^
			// list[i]

			// Don't use ensureCapacity() to save on copying.
			// NOTE: This has no measurable impact on performance,
			// but it might help in some usage patterns.
			if (len + 2 > list.length) {
				int[] temp = new int[len + 2 + GROW_EXTRA];
				if (i != 0)
					System.arraycopy(list, 0, temp, 0, i);
				System.arraycopy(list, i, temp, i + 2, len - i);
				list = temp;
			} else {
				System.arraycopy(list, i, list, i + 2, len - i);
			}

			list[i] = c;
			list[i + 1] = c + 1;
			len += 2;
		}

		return this;
	}

	// for internal use, after checkFrozen has been called
	private UnicodeSet add_unchecked(int start, int end) {
		if (start < MIN_VALUE || start > MAX_VALUE) {
			throw new IllegalArgumentException("Invalid code point U+" + Utility.hex(start, 6));
		}
		if (end < MIN_VALUE || end > MAX_VALUE) {
			throw new IllegalArgumentException("Invalid code point U+" + Utility.hex(end, 6));
		}
		if (start < end) {
			add(range(start, end), 2, 0);
		} else if (start == end) {
			add(start);
		}
		return this;
	}

	/**
	 * Generic filter-based scanning code for UCD property UnicodeSets.
	 */
	private UnicodeSet applyFilter(Filter filter, int src) {
		// Logically, walk through all Unicode characters, noting the start
		// and end of each range for which filter.contain(c) is
		// true. Add each range to a set.
		//
		// To improve performance, use an inclusions set which
		// encodes information about character ranges that are known
		// to have identical properties.
		// getInclusions(src) contains exactly the first characters of
		// same-value ranges for the given properties "source".

		clear();

		int startHasProperty = -1;
		UnicodeSet inclusions = getInclusions(src);
		int limitRange = inclusions.getRangeCount();

		for (int j = 0; j < limitRange; ++j) {
			// get current range
			int start = inclusions.getRangeStart(j);
			int end = inclusions.getRangeEnd(j);

			// for all the code points in the range, process
			for (int ch = start; ch <= end; ++ch) {
				// only add to the unicodeset on inflection points --
				// where the hasProperty value changes to false
				if (filter.contains(ch)) {
					if (startHasProperty < 0) {
						startHasProperty = ch;
					}
				} else if (startHasProperty >= 0) {
					add_unchecked(startHasProperty, ch - 1);
					startHasProperty = -1;
				}
			}
		}
		if (startHasProperty >= 0) {
			add_unchecked(startHasProperty, 0x10FFFF);
		}

		return this;
	}

	/**
	 * Parses the given pattern, starting at the given position. The character at
	 * pattern.charAt(pos.getIndex()) must be '[', or the parse fails. Parsing
	 * continues until the corresponding closing ']'. If a syntax error is
	 * encountered between the opening and closing brace, the parse fails. Upon
	 * return from a successful parse, the ParsePosition is updated to point to the
	 * character following the closing ']', and an inversion list for the parsed
	 * pattern is returned. This method calls itself recursively to parse embedded
	 * subpatterns.
	 *
	 * @param pattern the string containing the pattern to be parsed. The portion of
	 *                the string from pos.getIndex(), which must be a '[', to the
	 *                corresponding closing ']', is parsed.
	 * @param pos     upon entry, the position at which to being parsing. The
	 *                character at pattern.charAt(pos.getIndex()) must be a '['.
	 *                Upon return from a successful parse, pos.getIndex() is either
	 *                the character after the closing ']' of the parsed pattern, or
	 *                pattern.length() if the closing ']' is the last character of
	 *                the pattern string.
	 * @return an inversion list for the parsed substring of <code>pattern</code>
	 * @exception java.lang.IllegalArgumentException if the parse fails.
	 */
	private UnicodeSet applyPattern(String pattern, ParsePosition pos) {
		if ("[:age=3.2:]".equals(pattern)) {
			checkFrozen();
			VersionInfo version = VersionInfo.getInstance("3.2");
			applyFilter(new VersionFilter(version), UCharacterProperty.SRC_PROPSVEC);
		} else {
			throw new IllegalStateException("UnicodeSet.applyPattern(unexpected pattern " + pattern + ")");
		}

		return this;
	}

	// internal function
	private void checkFrozen() {
		if (isFrozen()) {
			throw new UnsupportedOperationException("Attempt to modify frozen object");
		}
	}

	// ----------------------------------------------------------------
	// Implementation: Pattern parsing
	// ----------------------------------------------------------------

	/**
	 * Removes all of the elements from this set. This set will be empty after this
	 * call returns.
	 *
	 * @stable ICU 2.0
	 */
	public UnicodeSet clear() {
		checkFrozen();
		list[0] = HIGH;
		len = 1;
		strings.clear();
		return this;
	}

	// ----------------------------------------------------------------
	// Implementation: Utility methods
	// ----------------------------------------------------------------

	/**
	 * Clone a thawed version of this class, according to the Freezable interface.
	 *
	 * @return the clone, not frozen
	 * @stable ICU 4.4
	 */
	public UnicodeSet cloneAsThawed() {
		UnicodeSet result = new UnicodeSet(this);
		assert !result.isFrozen();
		return result;
	}

	/**
	 * Complements the specified range in this set. Any character in the range will
	 * be removed if it is in this set, or will be added if it is not in this set.
	 * If {@code end > start} then an empty range is complemented, leaving the set
	 * unchanged.
	 *
	 * @param start first character, inclusive, of range to be removed from this
	 *              set.
	 * @param end   last character, inclusive, of range to be removed from this set.
	 * @stable ICU 2.0
	 */
	public UnicodeSet complement(int start, int end) {
		checkFrozen();
		if (start < MIN_VALUE || start > MAX_VALUE) {
			throw new IllegalArgumentException("Invalid code point U+" + Utility.hex(start, 6));
		}
		if (end < MIN_VALUE || end > MAX_VALUE) {
			throw new IllegalArgumentException("Invalid code point U+" + Utility.hex(end, 6));
		}
		if (start <= end) {
			xor(range(start, end), 2, 0);
		}
		return this;
	}

	/**
	 * Returns true if this set contains the given character.
	 *
	 * @param c character to be checked for containment
	 * @return true if the test condition is met
	 * @stable ICU 2.0
	 */
	public boolean contains(int c) {
		if (c < MIN_VALUE || c > MAX_VALUE) {
			throw new IllegalArgumentException("Invalid code point U+" + Utility.hex(c, 6));
		}
		if (bmpSet != null) {
			return bmpSet.contains(c);
		}
		if (stringSpan != null) {
			return stringSpan.contains(c);
		}

		/*
		 * // Set i to the index of the start item greater than ch // We know we will
		 * terminate without length test! int i = -1; while (true) { if (c < list[++i])
		 * break; }
		 */

		int i = findCodePoint(c);

		return ((i & 1) != 0); // return true if odd
	}

	// ----------------------------------------------------------------
	// Implementation: Fundamental operations
	// ----------------------------------------------------------------

	// polarity = 0, 3 is normal: x xor y
	// polarity = 1, 2: x xor ~y == x === y

	private void ensureBufferCapacity(int newLen) {
		if (buffer != null && newLen <= buffer.length)
			return;
		buffer = new int[newLen + GROW_EXTRA];
	}

	// polarity = 0 is normal: x union y
	// polarity = 2: x union ~y
	// polarity = 1: ~x union y
	// polarity = 3: ~x union ~y

	private void ensureCapacity(int newLen) {
		if (newLen <= list.length)
			return;
		int[] temp = new int[newLen + GROW_EXTRA];
		System.arraycopy(list, 0, temp, 0, len);
		list = temp;
	}

	// polarity = 0 is normal: x intersect y
	// polarity = 2: x intersect ~y == set-minus
	// polarity = 1: ~x intersect y
	// polarity = 3: ~x intersect ~y

	/**
	 * Returns the smallest value i such that c < list[i]. Caller must ensure that c
	 * is a legal value or this method will enter an infinite loop. This method
	 * performs a binary search.
	 *
	 * @param c a character in the range MIN_VALUE..MAX_VALUE inclusive
	 * @return the smallest integer i in the range 0..len-1, inclusive, such that c
	 *         < list[i]
	 */
	private final int findCodePoint(int c) {
		/*
		 * Examples: findCodePoint(c) set list[] c=0 1 3 4 7 8 === ==============
		 * =========== [] [110000] 0 0 0 0 0 0 [\u0000-\u0003] [0, 4, 110000] 1 1 1 2 2
		 * 2 [\u0004-\u0007] [4, 8, 110000] 0 0 0 1 1 2 [:all:] [0, 110000] 1 1 1 1 1 1
		 */

		// Return the smallest i such that c < list[i]. Assume
		// list[len - 1] == HIGH and that c is legal (0..HIGH-1).
		if (c < list[0])
			return 0;
		// High runner test. c is often after the last range, so an
		// initial check for this condition pays off.
		if (len >= 2 && c >= list[len - 2])
			return len - 1;
		int lo = 0;
		int hi = len - 1;
		// invariant: c >= list[lo]
		// invariant: c < list[hi]
		for (;;) {
			int i = (lo + hi) >>> 1;
			if (i == lo)
				return hi;
			if (c < list[i]) {
				hi = i;
			} else {
				lo = i;
			}
		}
	}

	/**
	 * Freeze this class, according to the Freezable interface.
	 *
	 * @return this
	 * @stable ICU 4.4
	 */
	public UnicodeSet freeze() {
		if (!isFrozen()) {
			// Do most of what compact() does before freezing because
			// compact() will not work when the set is frozen.
			// Small modification: Don't shrink if the savings would be tiny (<=GROW_EXTRA).

			// Delete buffer first to defragment memory less.
			buffer = null;
			if (list.length > (len + GROW_EXTRA)) {
				// Make the capacity equal to len or 1.
				// We don't want to realloc of 0 size.
				int capacity = (len == 0) ? 1 : len;
				int[] oldList = list;
				list = new int[capacity];
				for (int i = capacity; i-- > 0;) {
					list[i] = oldList[i];
				}
			}

			// Optimize contains() and span() and similar functions.
			if (!strings.isEmpty()) {
				stringSpan = new UnicodeSetStringSpan(this, new ArrayList<String>(strings), UnicodeSetStringSpan.ALL);
			}
			if (stringSpan == null || !stringSpan.needsStringSpanUTF16()) {
				// Optimize for code point spans.
				// There are no strings, or
				// all strings are irrelevant for span() etc. because
				// all of each string's code points are contained in this set.
				// However, fully contained strings are relevant for spanAndCount(),
				// so we create both objects.
				bmpSet = new BMPSet(list, len);
			}
		}
		return this;
	}

	// ----------------------------------------------------------------
	// Generic filter-based scanning code
	// ----------------------------------------------------------------

	/**
	 * Iteration method that returns the number of ranges contained in this set.
	 *
	 * @see #getRangeStart
	 * @see #getRangeEnd
	 * @stable ICU 2.0
	 */
	public int getRangeCount() {
		return len / 2;
	}

	/**
	 * Iteration method that returns the last character in the specified range of
	 * this set.
	 *
	 * @exception ArrayIndexOutOfBoundsException if index is outside the range
	 *                                           <code>0..getRangeCount()-1</code>
	 * @see #getRangeStart
	 * @see #getRangeEnd
	 * @stable ICU 2.0
	 */
	public int getRangeEnd(int index) {
		return (list[index * 2 + 1] - 1);
	}

	/**
	 * Iteration method that returns the first character in the specified range of
	 * this set.
	 *
	 * @exception ArrayIndexOutOfBoundsException if index is outside the range
	 *                                           <code>0..getRangeCount()-1</code>
	 * @see #getRangeCount
	 * @see #getRangeEnd
	 * @stable ICU 2.0
	 */
	public int getRangeStart(int index) {
		return list[index * 2];
	}

	/**
	 * Is this frozen, according to the Freezable interface?
	 *
	 * @return value
	 * @stable ICU 3.8
	 */
	public boolean isFrozen() {
		return (bmpSet != null || stringSpan != null);
	}

	/**
	 * Assumes start <= end.
	 */
	private int[] range(int start, int end) {
		if (rangeList == null) {
			rangeList = new int[] { start, end + 1, HIGH };
		} else {
			rangeList[0] = start;
			rangeList[1] = end + 1;
		}
		return rangeList;
	}

	private UnicodeSet retain(int[] other, int otherLen, int polarity) {
		ensureBufferCapacity(len + otherLen);
		int i = 0, j = 0, k = 0;
		int a = list[i++];
		int b = other[j++];
		// change from xor is that we have to check overlapping pairs
		// polarity bit 1 means a is second, bit 2 means b is.
		main: while (true) {
			switch (polarity) {
			case 0: // both first; drop the smaller
				if (a < b) { // drop a
					a = list[i++];
					polarity ^= 1;
				} else if (b < a) { // drop b
					b = other[j++];
					polarity ^= 2;
				} else { // a == b, take one, drop other
					if (a == HIGH)
						break main;
					buffer[k++] = a;
					a = list[i++];
					polarity ^= 1;
					b = other[j++];
					polarity ^= 2;
				}
				break;
			case 3: // both second; take lower if unequal
				if (a < b) { // take a
					buffer[k++] = a;
					a = list[i++];
					polarity ^= 1;
				} else if (b < a) { // take b
					buffer[k++] = b;
					b = other[j++];
					polarity ^= 2;
				} else { // a == b, take one, drop other
					if (a == HIGH)
						break main;
					buffer[k++] = a;
					a = list[i++];
					polarity ^= 1;
					b = other[j++];
					polarity ^= 2;
				}
				break;
			case 1: // a second, b first;
				if (a < b) { // NO OVERLAP, drop a
					a = list[i++];
					polarity ^= 1;
				} else if (b < a) { // OVERLAP, take b
					buffer[k++] = b;
					b = other[j++];
					polarity ^= 2;
				} else { // a == b, drop both!
					if (a == HIGH)
						break main;
					a = list[i++];
					polarity ^= 1;
					b = other[j++];
					polarity ^= 2;
				}
				break;
			case 2: // a first, b second; if a < b, overlap
				if (b < a) { // no overlap, drop b
					b = other[j++];
					polarity ^= 2;
				} else if (a < b) { // OVERLAP, take a
					buffer[k++] = a;
					a = list[i++];
					polarity ^= 1;
				} else { // a == b, drop both!
					if (a == HIGH)
						break main;
					a = list[i++];
					polarity ^= 1;
					b = other[j++];
					polarity ^= 2;
				}
				break;
			}
		}
		buffer[k++] = HIGH; // terminate
		len = k;
		// swap list and buffer
		int[] temp = list;
		list = buffer;
		buffer = temp;
		return this;
	}

	/**
	 * Retains only the elements in this set that are contained in the specified
	 * set. In other words, removes from this set all of its elements that are not
	 * contained in the specified set. This operation effectively modifies this set
	 * so that its value is the <i>intersection</i> of the two sets.
	 *
	 * @param c set that defines which elements this set will retain.
	 * @stable ICU 2.0
	 */
	public UnicodeSet retainAll(UnicodeSet c) {
		checkFrozen();
		retain(c.list, c.len, 0);
		strings.retainAll(c.strings);
		return this;
	}

	/**
	 * Make this object represent the same set as <code>other</code>.
	 *
	 * @param other a <code>UnicodeSet</code> whose value will be copied to this
	 *              object
	 * @stable ICU 2.0
	 */
	public UnicodeSet set(UnicodeSet other) {
		checkFrozen();
		list = other.list.clone();
		len = other.len;
		strings = new TreeSet<String>(other.strings);
		return this;
	}

	/**
	 * Returns the number of elements in this set (its cardinality) Note than the
	 * elements of a set may include both individual codepoints and strings.
	 *
	 * @return the number of elements in this set (its cardinality).
	 * @stable ICU 2.0
	 */
	public int size() {
		int n = 0;
		int count = getRangeCount();
		for (int i = 0; i < count; ++i) {
			n += getRangeEnd(i) - getRangeStart(i) + 1;
		}
		return n + strings.size();
	}

	/**
	 * Span a string using this UnicodeSet. If the start index is less than 0, span
	 * will start from 0. If the start index is greater than the string length, span
	 * returns the string length.
	 * <p>
	 * To replace, count elements, or delete spans, see
	 * {@link com.ibm.icu.text.UnicodeSetSpanner UnicodeSetSpanner}.
	 *
	 * @param s             The string to be spanned
	 * @param start         The start index that the span begins
	 * @param spanCondition The span condition
	 * @return the string index which ends the span (i.e. exclusive)
	 * @stable ICU 4.4
	 */
	public int span(CharSequence s, int start, SpanCondition spanCondition) {
		int end = s.length();
		if (start < 0) {
			start = 0;
		} else if (start >= end) {
			return end;
		}
		if (bmpSet != null) {
			// Frozen set without strings, or no string is relevant for span().
			return bmpSet.span(s, start, spanCondition, null);
		}
		if (stringSpan != null) {
			return stringSpan.span(s, start, spanCondition);
		} else if (!strings.isEmpty()) {
			int which = spanCondition == SpanCondition.NOT_CONTAINED ? UnicodeSetStringSpan.FWD_UTF16_NOT_CONTAINED
					: UnicodeSetStringSpan.FWD_UTF16_CONTAINED;
			UnicodeSetStringSpan strSpan = new UnicodeSetStringSpan(this, new ArrayList<String>(strings), which);
			if (strSpan.needsStringSpanUTF16()) {
				return strSpan.span(s, start, spanCondition);
			}
		}

		return spanCodePointsAndCount(s, start, spanCondition, null);
	}

	/**
	 * Span a string using this UnicodeSet.
	 * <p>
	 * To replace, count elements, or delete spans, see
	 * {@link com.ibm.icu.text.UnicodeSetSpanner UnicodeSetSpanner}.
	 *
	 * @param s             The string to be spanned
	 * @param spanCondition The span condition
	 * @return the length of the span
	 * @stable ICU 4.4
	 */
	public int span(CharSequence s, SpanCondition spanCondition) {
		return span(s, 0, spanCondition);
	}

	/**
	 * Same as span() but also counts the smallest number of set elements on any
	 * path across the span.
	 * <p>
	 * To replace, count elements, or delete spans, see
	 * {@link com.ibm.icu.text.UnicodeSetSpanner UnicodeSetSpanner}.
	 *
	 * @param outCount An output-only object (must not be null) for returning the
	 *                 count.
	 * @return the limit (exclusive end) of the span
	 */
	public int spanAndCount(CharSequence s, int start, SpanCondition spanCondition, OutputInt outCount) {
		if (outCount == null) {
			throw new IllegalArgumentException("outCount must not be null");
		}
		int end = s.length();
		if (start < 0) {
			start = 0;
		} else if (start >= end) {
			return end;
		}
		if (stringSpan != null) {
			// We might also have bmpSet != null,
			// but fully-contained strings are relevant for counting elements.
			return stringSpan.spanAndCount(s, start, spanCondition, outCount);
		} else if (bmpSet != null) {
			return bmpSet.span(s, start, spanCondition, outCount);
		} else if (!strings.isEmpty()) {
			int which = spanCondition == SpanCondition.NOT_CONTAINED ? UnicodeSetStringSpan.FWD_UTF16_NOT_CONTAINED
					: UnicodeSetStringSpan.FWD_UTF16_CONTAINED;
			which |= UnicodeSetStringSpan.WITH_COUNT;
			UnicodeSetStringSpan strSpan = new UnicodeSetStringSpan(this, new ArrayList<String>(strings), which);
			return strSpan.spanAndCount(s, start, spanCondition, outCount);
		}

		return spanCodePointsAndCount(s, start, spanCondition, outCount);
	}

	/**
	 * Span a string backwards (from the fromIndex) using this UnicodeSet. If the
	 * fromIndex is less than 0, spanBack will return 0. If fromIndex is greater
	 * than the string length, spanBack will start from the string length.
	 * <p>
	 * To replace, count elements, or delete spans, see
	 * {@link com.ibm.icu.text.UnicodeSetSpanner UnicodeSetSpanner}.
	 *
	 * @param s             The string to be spanned
	 * @param fromIndex     The index of the char (exclusive) that the string should
	 *                      be spanned backwards
	 * @param spanCondition The span condition
	 * @return The string index which starts the span (i.e. inclusive).
	 * @stable ICU 4.4
	 */
	public int spanBack(CharSequence s, int fromIndex, SpanCondition spanCondition) {
		if (fromIndex <= 0) {
			return 0;
		}
		if (fromIndex > s.length()) {
			fromIndex = s.length();
		}
		if (bmpSet != null) {
			// Frozen set without strings, or no string is relevant for spanBack().
			return bmpSet.spanBack(s, fromIndex, spanCondition);
		}
		if (stringSpan != null) {
			return stringSpan.spanBack(s, fromIndex, spanCondition);
		} else if (!strings.isEmpty()) {
			int which = (spanCondition == SpanCondition.NOT_CONTAINED) ? UnicodeSetStringSpan.BACK_UTF16_NOT_CONTAINED
					: UnicodeSetStringSpan.BACK_UTF16_CONTAINED;
			UnicodeSetStringSpan strSpan = new UnicodeSetStringSpan(this, new ArrayList<String>(strings), which);
			if (strSpan.needsStringSpanUTF16()) {
				return strSpan.spanBack(s, fromIndex, spanCondition);
			}
		}

		// Pin to 0/1 values.
		boolean spanContained = (spanCondition != SpanCondition.NOT_CONTAINED);

		int c;
		int prev = fromIndex;
		do {
			c = Character.codePointBefore(s, prev);
			if (spanContained != contains(c)) {
				break;
			}
			prev -= Character.charCount(c);
		} while (prev > 0);
		return prev;
	}

	private int spanCodePointsAndCount(CharSequence s, int start, SpanCondition spanCondition, OutputInt outCount) {
		// Pin to 0/1 values.
		boolean spanContained = (spanCondition != SpanCondition.NOT_CONTAINED);

		int c;
		int next = start;
		int length = s.length();
		int count = 0;
		do {
			c = Character.codePointAt(s, next);
			if (spanContained != contains(c)) {
				break;
			}
			++count;
			next += Character.charCount(c);
		} while (next < length);
		if (outCount != null) {
			outCount.value = count;
		}
		return next;
	}

	private UnicodeSet xor(int[] other, int otherLen, int polarity) {
		ensureBufferCapacity(len + otherLen);
		int i = 0, j = 0, k = 0;
		int a = list[i++];
		int b;
		if (polarity == 1 || polarity == 2) {
			b = LOW;
			if (other[j] == LOW) { // skip base if already LOW
				++j;
				b = other[j];
			}
		} else {
			b = other[j++];
		}
		// simplest of all the routines
		// sort the values, discarding identicals!
		while (true) {
			if (a < b) {
				buffer[k++] = a;
				a = list[i++];
			} else if (b < a) {
				buffer[k++] = b;
				b = other[j++];
			} else if (a != HIGH) { // at this point, a == b
				// discard both values!
				a = list[i++];
				b = other[j++];
			} else { // DONE!
				buffer[k++] = HIGH;
				len = k;
				break;
			}
		}
		// swap list and buffer
		int[] temp = list;
		list = buffer;
		buffer = temp;
		return this;
	}

}
