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  /*
   * Copyright 1999-2002,2004,2005 The Apache Software Foundation.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package jaxp.sun.org.apache.xerces.internal.impl.xpath.regex;
  
  import java.text.CharacterIterator;
  import java.util.Locale;
  import java.util.Stack;
  
  import jaxp.sun.org.apache.xerces.internal.util.IntStack;
  
  /**
   * A regular expression matching engine using Non-deterministic Finite Automaton (NFA).
   * This engine does not conform to the POSIX regular expression.
   *
   * <hr width="50%">
   * <h3>How to use</h3>
   *
   * <dl>
   *   <dt>A. Standard way
   *   <dd>
   * <pre>
   * RegularExpression re = new RegularExpression(<var>regex</var>);
   * if (re.matches(text)) { ... }
   * </pre>
   *
   *   <dt>B. Capturing groups
   *   <dd>
   * <pre>
   * RegularExpression re = new RegularExpression(<var>regex</var>);
   * Match match = new Match();
   * if (re.matches(text, match)) {
   *     ... // You can refer captured texts with methods of the <code>Match</code> class.
   * }
   * </pre>
   *
   * </dl>
   *
   * <h4>Case-insensitive matching</h4>
   * <pre>
   * RegularExpression re = new RegularExpression(<var>regex</var>, "i");
   * if (re.matches(text) >= 0) { ...}
   * </pre>
   *
   * <h4>Options</h4>
   * <p>You can specify options to <a href="#RegularExpression(java.lang.String, java.lang.String)"><code>RegularExpression(</code><var>regex</var><code>, </code><var>options</var><code>)</code></a>
   *    or <a href="#setPattern(java.lang.String, java.lang.String)"><code>setPattern(</code><var>regex</var><code>, </code><var>options</var><code>)</code></a>.
   *    This <var>options</var> parameter consists of the following characters.
   * </p>
   * <dl>
   *   <dt><a name="I_OPTION"><code>"i"</code></a>
   *   <dd>This option indicates case-insensitive matching.
   *   <dt><a name="M_OPTION"><code>"m"</code></a>
   *   <dd class="REGEX"><kbd>^</kbd> and <kbd>$</kbd> consider the EOL characters within the text.
   *   <dt><a name="S_OPTION"><code>"s"</code></a>
   *   <dd class="REGEX"><kbd>.</kbd> matches any one character.
   *   <dt><a name="U_OPTION"><code>"u"</code></a>
   *   <dd class="REGEX">Redefines <Kbd>\d \D \w \W \s \S \b \B \&lt; \></kbd> as becoming to Unicode.
   *   <dt><a name="W_OPTION"><code>"w"</code></a>
   *   <dd class="REGEX">By this option, <kbd>\b \B \&lt; \></kbd> are processed with the method of
   *      'Unicode Regular Expression Guidelines' Revision 4.
   *      When "w" and "u" are specified at the same time,
   *      <kbd>\b \B \&lt; \></kbd> are processed for the "w" option.
   *   <dt><a name="COMMA_OPTION"><code>","</code></a>
   *   <dd>The parser treats a comma in a character class as a range separator.
   *      <kbd class="REGEX">[a,b]</kbd> matches <kbd>a</kbd> or <kbd>,</kbd> or <kbd>b</kbd> without this option.
   *      <kbd class="REGEX">[a,b]</kbd> matches <kbd>a</kbd> or <kbd>b</kbd> with this option.
   *
   *   <dt><a name="X_OPTION"><code>"X"</code></a>
   *   <dd class="REGEX">
   *       By this option, the engine confoms to <a href="http://www.w3.org/TR/2000/WD-xmlschema-2-20000407/#regexs">XML Schema: Regular Expression</a>.
   *       The <code>match()</code> method does not do subsring matching
   *       but entire string matching.
   *
   * </dl>
   *
   * <hr width="50%">
   * <h3>Syntax</h3>
   * <table border="1" bgcolor="#ddeeff">
   *   <tr>
   *    <td>
   *     <h4>Differences from the Perl 5 regular expression</h4>
   *     <ul>
   *      <li>There is 6-digit hexadecimal character representation  (<kbd>\u005cv</kbd><var>HHHHHH</var>.)
   *      <li>Supports subtraction, union, and intersection operations for character classes.
   *      <li>Not supported: <kbd>\</kbd><var>ooo</var> (Octal character representations),
   *          <Kbd>\G</kbd>, <kbd>\C</kbd>, <kbd>\l</kbd><var>c</var>,
   *          <kbd>\u005c u</kbd><var>c</var>, <kbd>\L</kbd>, <kbd>\U</kbd>,
   *          <kbd>\E</kbd>, <kbd>\Q</kbd>, <kbd>\N{</kbd><var>name</var><kbd>}</kbd>,
   *          <Kbd>(?{<kbd><var>code</var><kbd>})</kbd>, <Kbd>(??{<kbd><var>code</var><kbd>})</kbd>
   *     </ul>
   *    </td>
   *   </tr>
   * </table>
   *
   * <P>Meta characters are `<KBD>. * + ? { [ ( ) | \ ^ $</KBD>'.</P>
   * <ul>
   *   <li>Character
   *     <dl>
   *       <dt class="REGEX"><kbd>.</kbd> (A period)
   *       <dd>Matches any one character except the following characters.
   *       <dd>LINE FEED (U+000A), CARRIAGE RETURN (U+000D),
   *           PARAGRAPH SEPARATOR (U+2029), LINE SEPARATOR (U+2028)
   *       <dd>This expression matches one code point in Unicode. It can match a pair of surrogates.
   *       <dd>When <a href="#S_OPTION">the "s" option</a> is specified,
   *           it matches any character including the above four characters.
   *
   *       <dt class="REGEX"><Kbd>\e \f \n \r \t</kbd>
   *       <dd>Matches ESCAPE (U+001B), FORM FEED (U+000C), LINE FEED (U+000A),
   *           CARRIAGE RETURN (U+000D), HORIZONTAL TABULATION (U+0009)
   *
   *       <dt class="REGEX"><kbd>\c</kbd><var>C</var>
   *       <dd>Matches a control character.
   *           The <var>C</var> must be one of '<kbd>@</kbd>', '<kbd>A</kbd>'-'<kbd>Z</kbd>',
   *           '<kbd>[</kbd>', '<kbd>\u005c</kbd>', '<kbd>]</kbd>', '<kbd>^</kbd>', '<kbd>_</kbd>'.
   *           It matches a control character of which the character code is less than
   *           the character code of the <var>C</var> by 0x0040.
   *       <dd class="REGEX">For example, a <kbd>\cJ</kbd> matches a LINE FEED (U+000A),
   *           and a <kbd>\c[</kbd> matches an ESCAPE (U+001B).
   *
   *       <dt class="REGEX">a non-meta character
   *       <dd>Matches the character.
   *
   *       <dt class="REGEX"><KBD>\</KBD> + a meta character
   *       <dd>Matches the meta character.
   *
   *       <dt class="REGEX"><kbd>\u005cx</kbd><var>HH</var> <kbd>\u005cx{</kbd><var>HHHH</var><kbd>}</kbd>
   *       <dd>Matches a character of which code point is <var>HH</var> (Hexadecimal) in Unicode.
   *           You can write just 2 digits for <kbd>\u005cx</kbd><var>HH</var>, and
   *           variable length digits for <kbd>\u005cx{</kbd><var>HHHH</var><kbd>}</kbd>.
   *
   *       <!--
   *       <dt class="REGEX"><kbd>\u005c u</kbd><var>HHHH</var>
   *       <dd>Matches a character of which code point is <var>HHHH</var> (Hexadecimal) in Unicode.
   *       -->
   *
   *       <dt class="REGEX"><kbd>\u005cv</kbd><var>HHHHHH</var>
   *       <dd>Matches a character of which code point is <var>HHHHHH</var> (Hexadecimal) in Unicode.
   *
   *       <dt class="REGEX"><kbd>\g</kbd>
   *       <dd>Matches a grapheme.
   *       <dd class="REGEX">It is equivalent to <kbd>(?[\p{ASSIGNED}]-[\p{M}\p{C}])?(?:\p{M}|[\x{094D}\x{09CD}\x{0A4D}\x{0ACD}\x{0B3D}\x{0BCD}\x{0C4D}\x{0CCD}\x{0D4D}\x{0E3A}\x{0F84}]\p{L}|[\x{1160}-\x{11A7}]|[\x{11A8}-\x{11FF}]|[\x{FF9E}\x{FF9F}])*</kbd>
   *
   *       <dt class="REGEX"><kbd>\X</kbd>
   *       <dd class="REGEX">Matches a combining character sequence.
   *       It is equivalent to <kbd>(?:\PM\pM*)</kbd>
   *     </dl>
   *   </li>
   *
   *   <li>Character class
   *     <dl>
  + *       <dt class="REGEX"><kbd>[</kbd><var>R<sub>1</sub></var><var>R<sub>2</sub></var><var>...</var><var>R<sub>n</sub></var><kbd>]</kbd> (without <a href="#COMMA_OPTION">"," option</a>)
  + *       <dt class="REGEX"><kbd>[</kbd><var>R<sub>1</sub></var><kbd>,</kbd><var>R<sub>2</sub></var><kbd>,</kbd><var>...</var><kbd>,</kbd><var>R<sub>n</sub></var><kbd>]</kbd> (with <a href="#COMMA_OPTION">"," option</a>)
   *       <dd>Positive character class.  It matches a character in ranges.
   *       <dd><var>R<sub>n</sub></var>:
   *       <ul>
   *         <li class="REGEX">A character (including <Kbd>\e \f \n \r \t</kbd> <kbd>\u005cx</kbd><var>HH</var> <kbd>\u005cx{</kbd><var>HHHH</var><kbd>}</kbd> <!--kbd>\u005c u</kbd><var>HHHH</var--> <kbd>\u005cv</kbd><var>HHHHHH</var>)
   *             <p>This range matches the character.
   *         <li class="REGEX"><var>C<sub>1</sub></var><kbd>-</kbd><var>C<sub>2</sub></var>
   *             <p>This range matches a character which has a code point that is >= <var>C<sub>1</sub></var>'s code point and &lt;= <var>C<sub>2</sub></var>'s code point.
  + *         <li class="REGEX">A POSIX character class: <Kbd>[:alpha:] [:alnum:] [:ascii:] [:cntrl:] [:digit:] [:graph:] [:lower:] [:print:] [:punct:] [:space:] [:upper:] [:xdigit:]</kbd>,
  + *             and negative POSIX character classes in Perl like <kbd>[:^alpha:]</kbd>
   *             <p>...
   *         <li class="REGEX"><kbd>\d \D \s \S \w \W \p{</kbd><var>name</var><kbd>} \P{</kbd><var>name</var><kbd>}</kbd>
   *             <p>These expressions specifies the same ranges as the following expressions.
   *       </ul>
   *       <p class="REGEX">Enumerated ranges are merged (union operation).
   *          <kbd>[a-ec-z]</kbd> is equivalent to <kbd>[a-z]</kbd>
   *
   *       <dt class="REGEX"><kbd>[^</kbd><var>R<sub>1</sub></var><var>R<sub>2</sub></var><var>...</var><var>R<sub>n</sub></var><kbd>]</kbd> (without a <a href="#COMMA_OPTION">"," option</a>)
   *       <dt class="REGEX"><kbd>[^</kbd><var>R<sub>1</sub></var><kbd>,</kbd><var>R<sub>2</sub></var><kbd>,</kbd><var>...</var><kbd>,</kbd><var>R<sub>n</sub></var><kbd>]</kbd> (with a <a href="#COMMA_OPTION">"," option</a>)
   *       <dd>Negative character class.  It matches a character not in ranges.
   *
   *       <dt class="REGEX"><kbd>(?[</kbd><var>ranges</var><kbd>]</kbd><var>op</var><kbd>[</kbd><var>ranges</var><kbd>]</kbd><var>op</var><kbd>[</kbd><var>ranges</var><kbd>]</kbd> ... <Kbd>)</kbd>
   *       (<var>op</var> is <kbd>-</kbd> or <kbd>+</kbd> or <kbd>&</kbd>.)
   *       <dd>Subtraction or union or intersection for character classes.
   *       <dd class="REGEX">For exmaple, <kbd>(?[A-Z]-[CF])</kbd> is equivalent to <kbd>[A-BD-EG-Z]</kbd>, and <kbd>(?[0x00-0x7f]-[K]&[\p{Lu}])</kbd> is equivalent to <kbd>[A-JL-Z]</kbd>.
   *       <dd>The result of this operations is a <u>positive character class</u>
   *           even if an expression includes any negative character classes.
   *           You have to take care on this in case-insensitive matching.
   *           For instance, <kbd>(?[^b])</kbd> is equivalent to <kbd>[\x00-ac-\x{10ffff}]</kbd>,
   *           which is equivalent to <kbd>[^b]</kbd> in case-sensitive matching.
   *           But, in case-insensitive matching, <kbd>(?[^b])</kbd> matches any character because
   *           it includes '<kbd>B</kbd>' and '<kbd>B</kbd>' matches '<kbd>b</kbd>'
   *           though <kbd>[^b]</kbd> is processed as <kbd>[^Bb]</kbd>.
   *
   *       <dt class="REGEX"><kbd>[</kbd><var>R<sub>1</sub>R<sub>2</sub>...</var><kbd>-[</kbd><var>R<sub>n</sub>R<sub>n+1</sub>...</var><kbd>]]</kbd> (with an <a href="#X_OPTION">"X" option</a>)</dt>
   *       <dd>Character class subtraction for the XML Schema.
   *           You can use this syntax when you specify an <a href="#X_OPTION">"X" option</a>.
   *
   *       <dt class="REGEX"><kbd>\d</kbd>
   *       <dd class="REGEX">Equivalent to <kbd>[0-9]</kbd>.
   *       <dd>When <a href="#U_OPTION">a "u" option</a> is set, it is equivalent to
   *           <span class="REGEX"><kbd>\p{Nd}</kbd></span>.
   *
   *       <dt class="REGEX"><kbd>\D</kbd>
   *       <dd class="REGEX">Equivalent to <kbd>[^0-9]</kbd>
   *       <dd>When <a href="#U_OPTION">a "u" option</a> is set, it is equivalent to
   *           <span class="REGEX"><kbd>\P{Nd}</kbd></span>.
   *
   *       <dt class="REGEX"><kbd>\s</kbd>
   *       <dd class="REGEX">Equivalent to <kbd>[ \f\n\r\t]</kbd>
   *       <dd>When <a href="#U_OPTION">a "u" option</a> is set, it is equivalent to
   *           <span class="REGEX"><kbd>[ \f\n\r\t\p{Z}]</kbd></span>.
   *
   *       <dt class="REGEX"><kbd>\S</kbd>
   *       <dd class="REGEX">Equivalent to <kbd>[^ \f\n\r\t]</kbd>
   *       <dd>When <a href="#U_OPTION">a "u" option</a> is set, it is equivalent to
   *           <span class="REGEX"><kbd>[^ \f\n\r\t\p{Z}]</kbd></span>.
   *
   *       <dt class="REGEX"><kbd>\w</kbd>
   *       <dd class="REGEX">Equivalent to <kbd>[a-zA-Z0-9_]</kbd>
   *       <dd>When <a href="#U_OPTION">a "u" option</a> is set, it is equivalent to
   *           <span class="REGEX"><kbd>[\p{Lu}\p{Ll}\p{Lo}\p{Nd}_]</kbd></span>.
   *
   *       <dt class="REGEX"><kbd>\W</kbd>
   *       <dd class="REGEX">Equivalent to <kbd>[^a-zA-Z0-9_]</kbd>
   *       <dd>When <a href="#U_OPTION">a "u" option</a> is set, it is equivalent to
   *           <span class="REGEX"><kbd>[^\p{Lu}\p{Ll}\p{Lo}\p{Nd}_]</kbd></span>.
   *
   *       <dt class="REGEX"><kbd>\p{</kbd><var>name</var><kbd>}</kbd>
   *       <dd>Matches one character in the specified General Category (the second field in <a href="ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.txt"><kbd>UnicodeData.txt</kbd></a>) or the specified <a href="ftp://ftp.unicode.org/Public/UNIDATA/Blocks.txt">Block</a>.
   *       The following names are available:
   *       <dl>
   *         <dt>Unicode General Categories:
   *         <dd><kbd>
   *       L, M, N, Z, C, P, S, Lu, Ll, Lt, Lm, Lo, Mn, Me, Mc, Nd, Nl, No, Zs, Zl, Zp,
   *       Cc, Cf, Cn, Co, Cs, Pd, Ps, Pe, Pc, Po, Sm, Sc, Sk, So,
   *         </kbd>
   *         <dd>(Currently the Cn category includes U+10000-U+10FFFF characters)
   *         <dt>Unicode Blocks:
   *         <dd><kbd>
   *       Basic Latin, Latin-1 Supplement, Latin Extended-A, Latin Extended-B,
   *       IPA Extensions, Spacing Modifier Letters, Combining Diacritical Marks, Greek,
   *       Cyrillic, Armenian, Hebrew, Arabic, Devanagari, Bengali, Gurmukhi, Gujarati,
   *       Oriya, Tamil, Telugu, Kannada, Malayalam, Thai, Lao, Tibetan, Georgian,
   *       Hangul Jamo, Latin Extended Additional, Greek Extended, General Punctuation,
   *       Superscripts and Subscripts, Currency Symbols, Combining Marks for Symbols,
   *       Letterlike Symbols, Number Forms, Arrows, Mathematical Operators,
   *       Miscellaneous Technical, Control Pictures, Optical Character Recognition,
   *       Enclosed Alphanumerics, Box Drawing, Block Elements, Geometric Shapes,
   *       Miscellaneous Symbols, Dingbats, CJK Symbols and Punctuation, Hiragana,
   *       Katakana, Bopomofo, Hangul Compatibility Jamo, Kanbun,
   *       Enclosed CJK Letters and Months, CJK Compatibility, CJK Unified Ideographs,
   *       Hangul Syllables, High Surrogates, High Private Use Surrogates, Low Surrogates,
   *       Private Use, CJK Compatibility Ideographs, Alphabetic Presentation Forms,
   *       Arabic Presentation Forms-A, Combining Half Marks, CJK Compatibility Forms,
   *       Small Form Variants, Arabic Presentation Forms-B, Specials,
   *       Halfwidth and Fullwidth Forms
   *         </kbd>
   *         <dt>Others:
   *         <dd><kbd>ALL</kbd> (Equivalent to <kbd>[\u005cu0000-\u005cv10FFFF]</kbd>)
   *         <dd><kbd>ASSGINED</kbd> (<kbd>\p{ASSIGNED}</kbd> is equivalent to <kbd>\P{Cn}</kbd>)
   *         <dd><kbd>UNASSGINED</kbd>
   *             (<kbd>\p{UNASSIGNED}</kbd> is equivalent to <kbd>\p{Cn}</kbd>)
   *       </dl>
   *
   *       <dt class="REGEX"><kbd>\P{</kbd><var>name</var><kbd>}</kbd>
   *       <dd>Matches one character not in the specified General Category or the specified Block.
   *     </dl>
   *   </li>
   *
   *   <li>Selection and Quantifier
   *     <dl>
   *       <dt class="REGEX"><VAR>X</VAR><kbd>|</kbd><VAR>Y</VAR>
   *       <dd>...
   *
   *       <dt class="REGEX"><VAR>X</VAR><kbd>*</KBD>
   *       <dd>Matches 0 or more <var>X</var>.
   *
   *       <dt class="REGEX"><VAR>X</VAR><kbd>+</KBD>
   *       <dd>Matches 1 or more <var>X</var>.
   *
   *       <dt class="REGEX"><VAR>X</VAR><kbd>?</KBD>
   *       <dd>Matches 0 or 1 <var>X</var>.
   *
   *       <dt class="REGEX"><var>X</var><kbd>{</kbd><var>number</var><kbd>}</kbd>
   *       <dd>Matches <var>number</var> times.
   *
   *       <dt class="REGEX"><var>X</var><kbd>{</kbd><var>min</var><kbd>,}</kbd>
   *       <dd>...
   *
   *       <dt class="REGEX"><var>X</var><kbd>{</kbd><var>min</var><kbd>,</kbd><var>max</var><kbd>}</kbd>
   *       <dd>...
   *
   *       <dt class="REGEX"><VAR>X</VAR><kbd>*?</kbd>
   *       <dt class="REGEX"><VAR>X</VAR><kbd>+?</kbd>
   *       <dt class="REGEX"><VAR>X</VAR><kbd>??</kbd>
   *       <dt class="REGEX"><var>X</var><kbd>{</kbd><var>min</var><kbd>,}?</kbd>
   *       <dt class="REGEX"><var>X</var><kbd>{</kbd><var>min</var><kbd>,</kbd><var>max</var><kbd>}?</kbd>
   *       <dd>Non-greedy matching.
   *     </dl>
   *   </li>
   *
   *   <li>Grouping, Capturing, and Back-reference
   *     <dl>
   *       <dt class="REGEX"><KBD>(?:</kbd><VAR>X</VAR><kbd>)</KBD>
   *       <dd>Grouping. "<KBD>foo+</KBD>" matches "<KBD>foo</KBD>" or "<KBD>foooo</KBD>".
   *       If you want it matches "<KBD>foofoo</KBD>" or "<KBD>foofoofoo</KBD>",
   *       you have to write "<KBD>(?:foo)+</KBD>".
   *
   *       <dt class="REGEX"><KBD>(</kbd><VAR>X</VAR><kbd>)</KBD>
   *       <dd>Grouping with capturing.
   * It make a group and applications can know
   * where in target text a group matched with methods of a <code>Match</code> instance
   * after <code><a href="#matches(java.lang.String, com.sun.org.apache.xerces.internal.utils.regex.Match)">matches(String,Match)</a></code>.
   * The 0th group means whole of this regular expression.
   * The <VAR>N</VAR>th gorup is the inside of the <VAR>N</VAR>th left parenthesis.
   *
   *   <p>For instance, a regular expression is
   *   "<FONT color=blue><KBD> *([^&lt;:]*) +&lt;([^&gt;]*)&gt; *</KBD></FONT>"
   *   and target text is
   *   "<FONT color=red><KBD>From: TAMURA Kent &lt;kent@trl.ibm.co.jp&gt;</KBD></FONT>":
   *   <ul>
   *     <li><code>Match.getCapturedText(0)</code>:
   *     "<FONT color=red><KBD> TAMURA Kent &lt;kent@trl.ibm.co.jp&gt;</KBD></FONT>"
   *     <li><code>Match.getCapturedText(1)</code>: "<FONT color=red><KBD>TAMURA Kent</KBD></FONT>"
   *     <li><code>Match.getCapturedText(2)</code>: "<FONT color=red><KBD>kent@trl.ibm.co.jp</KBD></FONT>"
   *   </ul>
   *
   *       <dt class="REGEX"><kbd>\1 \2 \3 \4 \5 \6 \7 \8 \9</kbd>
   *       <dd>
   *
   *       <dt class="REGEX"><kbd>(?></kbd><var>X</var><kbd>)</kbd>
   *       <dd>Independent expression group. ................
   *
   *       <dt class="REGEX"><kbd>(?</kbd><var>options</var><kbd>:</kbd><var>X</var><kbd>)</kbd>
   *       <dt class="REGEX"><kbd>(?</kbd><var>options</var><kbd>-</kbd><var>options2</var><kbd>:</kbd><var>X</var><kbd>)</kbd>
   *       <dd>............................
   *       <dd>The <var>options</var> or the <var>options2</var> consists of 'i' 'm' 's' 'w'.
   *           Note that it can not contain 'u'.
   *
   *       <dt class="REGEX"><kbd>(?</kbd><var>options</var><kbd>)</kbd>
   *       <dt class="REGEX"><kbd>(?</kbd><var>options</var><kbd>-</kbd><var>options2</var><kbd>)</kbd>
   *       <dd>......
   *       <dd>These expressions must be at the beginning of a group.
   *     </dl>
   *   </li>
   *
   *   <li>Anchor
   *     <dl>
   *       <dt class="REGEX"><kbd>\A</kbd>
   *       <dd>Matches the beginnig of the text.
   *
   *       <dt class="REGEX"><kbd>\Z</kbd>
   *       <dd>Matches the end of the text, or before an EOL character at the end of the text,
   *           or CARRIAGE RETURN + LINE FEED at the end of the text.
   *
   *       <dt class="REGEX"><kbd>\z</kbd>
   *       <dd>Matches the end of the text.
   *
   *       <dt class="REGEX"><kbd>^</kbd>
   *       <dd>Matches the beginning of the text.  It is equivalent to <span class="REGEX"><Kbd>\A</kbd></span>.
   *       <dd>When <a href="#M_OPTION">a "m" option</a> is set,
   *           it matches the beginning of the text, or after one of EOL characters (
   *           LINE FEED (U+000A), CARRIAGE RETURN (U+000D), LINE SEPARATOR (U+2028),
   *           PARAGRAPH SEPARATOR (U+2029).)
   *
   *       <dt class="REGEX"><kbd>$</kbd>
   *       <dd>Matches the end of the text, or before an EOL character at the end of the text,
   *           or CARRIAGE RETURN + LINE FEED at the end of the text.
   *       <dd>When <a href="#M_OPTION">a "m" option</a> is set,
   *           it matches the end of the text, or before an EOL character.
   *
   *       <dt class="REGEX"><kbd>\b</kbd>
   *       <dd>Matches word boundary.
   *           (See <a href="#W_OPTION">a "w" option</a>)
   *
   *       <dt class="REGEX"><kbd>\B</kbd>
   *       <dd>Matches non word boundary.
   *           (See <a href="#W_OPTION">a "w" option</a>)
   *
   *       <dt class="REGEX"><kbd>\&lt;</kbd>
   *       <dd>Matches the beginning of a word.
   *           (See <a href="#W_OPTION">a "w" option</a>)
   *
   *       <dt class="REGEX"><kbd>\&gt;</kbd>
   *       <dd>Matches the end of a word.
   *           (See <a href="#W_OPTION">a "w" option</a>)
   *     </dl>
   *   </li>
   *   <li>Lookahead and lookbehind
   *     <dl>
   *       <dt class="REGEX"><kbd>(?=</kbd><var>X</var><kbd>)</kbd>
   *       <dd>Lookahead.
   *
   *       <dt class="REGEX"><kbd>(?!</kbd><var>X</var><kbd>)</kbd>
   *       <dd>Negative lookahead.
   *
   *       <dt class="REGEX"><kbd>(?&lt;=</kbd><var>X</var><kbd>)</kbd>
   *       <dd>Lookbehind.
   *       <dd>(Note for text capturing......)
   *
   *       <dt class="REGEX"><kbd>(?&lt;!</kbd><var>X</var><kbd>)</kbd>
   *       <dd>Negative lookbehind.
   *     </dl>
   *   </li>
   *
   *   <li>Misc.
   *     <dl>
   *       <dt class="REGEX"><kbd>(?(</Kbd><var>condition</var><Kbd>)</kbd><var>yes-pattern</var><kbd>|</kbd><var>no-pattern</var><kbd>)</kbd>,
   *       <dt class="REGEX"><kbd>(?(</kbd><var>condition</var><kbd>)</kbd><var>yes-pattern</var><kbd>)</kbd>
   *       <dd>......
   *       <dt class="REGEX"><kbd>(?#</kbd><var>comment</var><kbd>)</kbd>
   *       <dd>Comment.  A comment string consists of characters except '<kbd>)</kbd>'.
   *           You can not write comments in character classes and before quantifiers.
   *     </dl>
   *   </li>
   * </ul>
   *
   *
   * <hr width="50%">
   * <h3>BNF for the regular expression</h3>
   * <pre>
   * regex ::= ('(?' options ')')? term ('|' term)*
   * term ::= factor+
   * factor ::= anchors | atom (('*' | '+' | '?' | minmax ) '?'? )?
   *            | '(?#' [^)]* ')'
   * minmax ::= '{' ([0-9]+ | [0-9]+ ',' | ',' [0-9]+ | [0-9]+ ',' [0-9]+) '}'
   * atom ::= char | '.' | char-class | '(' regex ')' | '(?:' regex ')' | '\' [0-9]
   *          | '\w' | '\W' | '\d' | '\D' | '\s' | '\S' | category-block | '\X'
   *          | '(?>' regex ')' | '(?' options ':' regex ')'
   *          | '(?' ('(' [0-9] ')' | '(' anchors ')' | looks) term ('|' term)? ')'
   * options ::= [imsw]* ('-' [imsw]+)?
   * anchors ::= '^' | '$' | '\A' | '\Z' | '\z' | '\b' | '\B' | '\&lt;' | '\>'
   * looks ::= '(?=' regex ')'  | '(?!' regex ')'
   *           | '(?&lt;=' regex ')' | '(?&lt;!' regex ')'
   * char ::= '\\' | '\' [efnrtv] | '\c' [@-_] | code-point | character-1
   * category-block ::= '\' [pP] category-symbol-1
   *                    | ('\p{' | '\P{') (category-symbol | block-name
   *                                       | other-properties) '}'
   * category-symbol-1 ::= 'L' | 'M' | 'N' | 'Z' | 'C' | 'P' | 'S'
   * category-symbol ::= category-symbol-1 | 'Lu' | 'Ll' | 'Lt' | 'Lm' | Lo'
   *                     | 'Mn' | 'Me' | 'Mc' | 'Nd' | 'Nl' | 'No'
   *                     | 'Zs' | 'Zl' | 'Zp' | 'Cc' | 'Cf' | 'Cn' | 'Co' | 'Cs'
   *                     | 'Pd' | 'Ps' | 'Pe' | 'Pc' | 'Po'
   *                     | 'Sm' | 'Sc' | 'Sk' | 'So'
   * block-name ::= (See above)
   * other-properties ::= 'ALL' | 'ASSIGNED' | 'UNASSIGNED'
   * character-1 ::= (any character except meta-characters)
   *
   * char-class ::= '[' ranges ']'
   *                | '(?[' ranges ']' ([-+&] '[' ranges ']')? ')'
   * ranges ::= '^'? (range <a href="#COMMA_OPTION">','?</a>)+
   * range ::= '\d' | '\w' | '\s' | '\D' | '\W' | '\S' | category-block
   *           | range-char | range-char '-' range-char
   * range-char ::= '\[' | '\]' | '\\' | '\' [,-efnrtv] | code-point | character-2
   * code-point ::= '\x' hex-char hex-char
   *                | '\x{' hex-char+ '}'
   * <!--               | '\u005c u' hex-char hex-char hex-char hex-char
   * -->               | '\v' hex-char hex-char hex-char hex-char hex-char hex-char
   * hex-char ::= [0-9a-fA-F]
   * character-2 ::= (any character except \[]-,)
   * </pre>
   *
   * <hr width="50%">
   * <h3>TODO</h3>
   * <ul>
   *   <li><a href="http://www.unicode.org/unicode/reports/tr18/">Unicode Regular Expression Guidelines</a>
   *     <ul>
   *       <li>2.4 Canonical Equivalents
   *       <li>Level 3
   *     </ul>
   *   <li>Parsing performance
   * </ul>
   *
   * <hr width="50%">
   *
   * @xerces.internal
   *
   * @author TAMURA Kent &lt;kent@trl.ibm.co.jp&gt;
   * @version $Id: RegularExpression.java,v 1.9 2010/07/27 05:02:34 joehw Exp $
   */
  public class RegularExpression implements java.io.Serializable {
  
      private static final long serialVersionUID = 6242499334195006401L;
  
      static final boolean DEBUG = false;
  
      /**
       * Compiles a token tree into an operation flow.
       */
      private synchronized void compile(Token tok) {
          if (this.operations != null)
              return;
          this.numberOfClosures = 0;
          this.operations = this.compile(tok, null, false);
      }
  
      /**
       * Converts a token to an operation.
       */
      private Op compile(Token tok, Op next, boolean reverse) {
          Op ret;
          switch (tok.type) {
          case Token.DOT:
              ret = Op.createDot();
              ret.next = next;
              break;
  
          case Token.CHAR:
              ret = Op.createChar(tok.getChar());
              ret.next = next;
              break;
  
          case Token.ANCHOR:
              ret = Op.createAnchor(tok.getChar());
              ret.next = next;
              break;
  
          case Token.RANGE:
          case Token.NRANGE:
              ret = Op.createRange(tok);
              ret.next = next;
              break;
  
          case Token.CONCAT:
              ret = next;
              if (!reverse) {
                  for (int i = tok.size()-1;  i >= 0;  i --) {
                      ret = compile(tok.getChild(i), ret, false);
                  }
              } else {
                  for (int i = 0;  i < tok.size();  i ++) {
                      ret = compile(tok.getChild(i), ret, true);
                  }
              }
              break;
  
          case Token.UNION:
              Op.UnionOp uni = Op.createUnion(tok.size());
              for (int i = 0;  i < tok.size();  i ++) {
                  uni.addElement(compile(tok.getChild(i), next, reverse));
              }
              ret = uni;                          // ret.next is null.
              break;
  
          case Token.CLOSURE:
          case Token.NONGREEDYCLOSURE:
              Token child = tok.getChild(0);
              int min = tok.getMin();
              int max = tok.getMax();
              if (min >= 0 && min == max) { // {n}
                  ret = next;
                  for (int i = 0; i < min;  i ++) {
                      ret = compile(child, ret, reverse);
                  }
                  break;
              }
              if (min > 0 && max > 0)
                  max -= min;
              if (max > 0) {
                  // X{2,6} -> XX(X(X(XX?)?)?)?
                  ret = next;
                  for (int i = 0;  i < max;  i ++) {
                      Op.ChildOp q = Op.createQuestion(tok.type == Token.NONGREEDYCLOSURE);
                      q.next = next;
                      q.setChild(compile(child, ret, reverse));
                      ret = q;
                  }
              } else {
                  Op.ChildOp op;
                  if (tok.type == Token.NONGREEDYCLOSURE) {
                      op = Op.createNonGreedyClosure();
                  } else {                        // Token.CLOSURE
                      op = Op.createClosure(this.numberOfClosures++);
                  }
                  op.next = next;
                  op.setChild(compile(child, op, reverse));
                  ret = op;
              }
              if (min > 0) {
                  for (int i = 0;  i < min;  i ++) {
                      ret = compile(child, ret, reverse);
                  }
              }
              break;
  
          case Token.EMPTY:
              ret = next;
              break;
  
          case Token.STRING:
              ret = Op.createString(tok.getString());
              ret.next = next;
              break;
  
          case Token.BACKREFERENCE:
              ret = Op.createBackReference(tok.getReferenceNumber());
              ret.next = next;
              break;
  
          case Token.PAREN:
              if (tok.getParenNumber() == 0) {
                  ret = compile(tok.getChild(0), next, reverse);
              } else if (reverse) {
                  next = Op.createCapture(tok.getParenNumber(), next);
                  next = compile(tok.getChild(0), next, reverse);
                  ret = Op.createCapture(-tok.getParenNumber(), next);
              } else {
                  next = Op.createCapture(-tok.getParenNumber(), next);
                  next = compile(tok.getChild(0), next, reverse);
                  ret = Op.createCapture(tok.getParenNumber(), next);
              }
              break;
  
          case Token.LOOKAHEAD:
              ret = Op.createLook(Op.LOOKAHEAD, next, compile(tok.getChild(0), null, false));
              break;
          case Token.NEGATIVELOOKAHEAD:
              ret = Op.createLook(Op.NEGATIVELOOKAHEAD, next, compile(tok.getChild(0), null, false));
              break;
          case Token.LOOKBEHIND:
              ret = Op.createLook(Op.LOOKBEHIND, next, compile(tok.getChild(0), null, true));
              break;
          case Token.NEGATIVELOOKBEHIND:
              ret = Op.createLook(Op.NEGATIVELOOKBEHIND, next, compile(tok.getChild(0), null, true));
              break;
  
          case Token.INDEPENDENT:
              ret = Op.createIndependent(next, compile(tok.getChild(0), null, reverse));
              break;
  
          case Token.MODIFIERGROUP:
              ret = Op.createModifier(next, compile(tok.getChild(0), null, reverse),
                                      ((Token.ModifierToken)tok).getOptions(),
                                      ((Token.ModifierToken)tok).getOptionsMask());
              break;
  
          case Token.CONDITION:
              Token.ConditionToken ctok = (Token.ConditionToken)tok;
              int ref = ctok.refNumber;
              Op condition = ctok.condition == null ? null : compile(ctok.condition, null, reverse);
              Op yes = compile(ctok.yes, next, reverse);
              Op no = ctok.no == null ? null : compile(ctok.no, next, reverse);
              ret = Op.createCondition(next, ref, condition, yes, no);
              break;
  
          default:
              throw new RuntimeException("Unknown token type: "+tok.type);
          } // switch (tok.type)
          return ret;
      }
  
  
  //Public
  
      /**
       * Checks whether the <var>target</var> text <strong>contains</strong> this pattern or not.
       *
       * @return true if the target is matched to this regular expression.
       */
      public boolean matches(char[]  target) {
          return this.matches(target, 0,  target .length , (Match)null);
      }
  
      /**
       * Checks whether the <var>target</var> text <strong>contains</strong> this pattern
       * in specified range or not.
       *
       * @param start Start offset of the range.
       * @param end  End offset +1 of the range.
       * @return true if the target is matched to this regular expression.
       */
      public boolean matches(char[]  target, int start, int end) {
          return this.matches(target, start, end, (Match)null);
      }
  
      /**
       * Checks whether the <var>target</var> text <strong>contains</strong> this pattern or not.
       *
       * @param match A Match instance for storing matching result.
       * @return Offset of the start position in <VAR>target</VAR>; or -1 if not match.
       */
      public boolean matches(char[]  target, Match match) {
          return this.matches(target, 0,  target .length , match);
      }
  
  
      /**
       * Checks whether the <var>target</var> text <strong>contains</strong> this pattern
       * in specified range or not.
       *
       * @param start Start offset of the range.
       * @param end  End offset +1 of the range.
       * @param match A Match instance for storing matching result.
       * @return Offset of the start position in <VAR>target</VAR>; or -1 if not match.
       */
      public boolean matches(char[] target, int start, int end, Match match) {
  
          synchronized (this) {
              if (this.operations == null)
                  this.prepare();
              if (this.context == null)
                  this.context = new Context();
          }
          Context con = null;
          synchronized (this.context) {
              con = this.context.inuse ? new Context() : this.context;
              con.reset(target, start, end, this.numberOfClosures);
          }
          if (match != null) {
              match.setNumberOfGroups(this.nofparen);
              match.setSource(target);
          } else if (this.hasBackReferences) {
              match = new Match();
              match.setNumberOfGroups(this.nofparen);
              // Need not to call setSource() because
              // a caller can not access this match instance.
          }
          con.match = match;
  
          if (RegularExpression.isSet(this.options, XMLSCHEMA_MODE)) {
              int matchEnd = this. match(con, this.operations, con.start, 1, this.options);
              //System.err.println("DEBUG: matchEnd="+matchEnd);
              if (matchEnd == con.limit) {
                  if (con.match != null) {
                      con.match.setBeginning(0, con.start);
                      con.match.setEnd(0, matchEnd);
                  }
                  con.setInUse(false);
                  return true;
              }
              return false;
          }
  
          /*
           * The pattern has only fixed string.
           * The engine uses Boyer-Moore.
           */
          if (this.fixedStringOnly) {
              //System.err.println("DEBUG: fixed-only: "+this.fixedString);
              int o = this.fixedStringTable.matches(target, con.start, con.limit);
              if (o >= 0) {
                  if (con.match != null) {
                      con.match.setBeginning(0, o);
                      con.match.setEnd(0, o+this.fixedString.length());
                  }
                  con.setInUse(false);
                  return true;
              }
              con.setInUse(false);
              return false;
          }
  
          /*
           * The pattern contains a fixed string.
           * The engine checks with Boyer-Moore whether the text contains the fixed string or not.
           * If not, it return with false.
           */
          if (this.fixedString != null) {
              int o = this.fixedStringTable.matches(target, con.start, con.limit);
              if (o < 0) {
                  //System.err.println("Non-match in fixed-string search.");
                  con.setInUse(false);
                  return false;
              }
          }
  
          int limit = con.limit-this.minlength;
          int matchStart;
          int matchEnd = -1;
  
          /*
           * Checks whether the expression starts with ".*".
           */
          if (this.operations != null
              && this.operations.type == Op.CLOSURE && this.operations.getChild().type == Op.DOT) {
              if (isSet(this.options, SINGLE_LINE)) {
                  matchStart = con.start;
                  matchEnd = this. match(con, this.operations, con.start, 1, this.options);
              } else {
                  boolean previousIsEOL = true;
                  for (matchStart = con.start;  matchStart <= limit;  matchStart ++) {
                      int ch =  target [  matchStart ] ;
                      if (isEOLChar(ch)) {
                          previousIsEOL = true;
                      } else {
                          if (previousIsEOL) {
                              if (0 <= (matchEnd = this. match(con, this.operations,
                                                               matchStart, 1, this.options)))
                                  break;
                          }
                          previousIsEOL = false;
                      }
                  }
              }
          }
  
          /*
           * Optimization against the first character.
           */
          else if (this.firstChar != null) {
              //System.err.println("DEBUG: with firstchar-matching: "+this.firstChar);
              RangeToken range = this.firstChar;
              for (matchStart = con.start;  matchStart <= limit;  matchStart ++) {
                  int ch =  target [matchStart] ;
                  if (REUtil.isHighSurrogate(ch) && matchStart+1 < con.limit) {
                      ch = REUtil.composeFromSurrogates(ch, target[matchStart+1]);
                  }
                  if (!range.match(ch))  {
                      continue;
                  }
                  if (0 <= (matchEnd = this. match(con, this.operations,
                                                   matchStart, 1, this.options))) {
                          break;
                  }
              }
          }
  
          /*
           * Straightforward matching.
           */
          else {
              for (matchStart = con.start;  matchStart <= limit;  matchStart ++) {
                  if (0 <= (matchEnd = this. match(con, this.operations, matchStart, 1, this.options)))
                      break;
              }
          }
  
          if (matchEnd >= 0) {
              if (con.match != null) {
                  con.match.setBeginning(0, matchStart);
                  con.match.setEnd(0, matchEnd);
              }
              con.setInUse(false);
              return true;
          } else {
              con.setInUse(false);
              return false;
          }
      }
  
      /**
       * Checks whether the <var>target</var> text <strong>contains</strong> this pattern or not.
       *
       * @return true if the target is matched to this regular expression.
       */
      public boolean matches(String  target) {
          return this.matches(target, 0,  target .length() , (Match)null);
      }
  
      /**
       * Checks whether the <var>target</var> text <strong>contains</strong> this pattern
       * in specified range or not.
       *
       * @param start Start offset of the range.
       * @param end  End offset +1 of the range.
       * @return true if the target is matched to this regular expression.
       */
      public boolean matches(String  target, int start, int end) {
          return this.matches(target, start, end, (Match)null);
      }
  
      /**
       * Checks whether the <var>target</var> text <strong>contains</strong> this pattern or not.
       *
       * @param match A Match instance for storing matching result.
       * @return Offset of the start position in <VAR>target</VAR>; or -1 if not match.
       */
      public boolean matches(String  target, Match match) {
          return this.matches(target, 0,  target .length() , match);
      }
  
      /**
       * Checks whether the <var>target</var> text <strong>contains</strong> this pattern
       * in specified range or not.
       *
       * @param start Start offset of the range.
       * @param end  End offset +1 of the range.
       * @param match A Match instance for storing matching result.
       * @return Offset of the start position in <VAR>target</VAR>; or -1 if not match.
       */
      public boolean matches(String  target, int start, int end, Match match) {
  
          synchronized (this) {
              if (this.operations == null)
                  this.prepare();
              if (this.context == null)
                  this.context = new Context();
          }
          Context con = null;
          synchronized (this.context) {
              con = this.context.inuse ? new Context() : this.context;
              con.reset(target, start, end, this.numberOfClosures);
          }
          if (match != null) {
              match.setNumberOfGroups(this.nofparen);
              match.setSource(target);
          } else if (this.hasBackReferences) {
              match = new Match();
              match.setNumberOfGroups(this.nofparen);
              // Need not to call setSource() because
              // a caller can not access this match instance.
          }
          con.match = match;
  
          if (RegularExpression.isSet(this.options, XMLSCHEMA_MODE)) {
              if (DEBUG) {
                  System.err.println("target string="+target);
              }
              int matchEnd = this. match(con, this.operations, con.start, 1, this.options);
              if (DEBUG) {
                  System.err.println("matchEnd="+matchEnd);
                  System.err.println("con.limit="+con.limit);
              }
              if (matchEnd == con.limit) {
                  if (con.match != null) {
                      con.match.setBeginning(0, con.start);
                      con.match.setEnd(0, matchEnd);
                  }
                  con.setInUse(false);
                  return true;
              }
              return false;
          }
  
          /*
           * The pattern has only fixed string.
           * The engine uses Boyer-Moore.
           */
          if (this.fixedStringOnly) {
              //System.err.println("DEBUG: fixed-only: "+this.fixedString);
              int o = this.fixedStringTable.matches(target, con.start, con.limit);
              if (o >= 0) {
                  if (con.match != null) {
                      con.match.setBeginning(0, o);
                      con.match.setEnd(0, o+this.fixedString.length());
                  }
                  con.setInUse(false);
                  return true;
              }
              con.setInUse(false);
              return false;
          }
  
          /*
           * The pattern contains a fixed string.
           * The engine checks with Boyer-Moore whether the text contains the fixed string or not.
           * If not, it return with false.
           */
          if (this.fixedString != null) {
              int o = this.fixedStringTable.matches(target, con.start, con.limit);
              if (o < 0) {
                  //System.err.println("Non-match in fixed-string search.");
                  con.setInUse(false);
                  return false;
              }
          }
  
          int limit = con.limit-this.minlength;
          int matchStart;
          int matchEnd = -1;
  
          /*
           * Checks whether the expression starts with ".*".
           */
          if (this.operations != null
              && this.operations.type == Op.CLOSURE && this.operations.getChild().type == Op.DOT) {
              if (isSet(this.options, SINGLE_LINE)) {
                  matchStart = con.start;
                  matchEnd = this.match(con, this.operations, con.start, 1, this.options);
              } else {
                  boolean previousIsEOL = true;
                  for (matchStart = con.start;  matchStart <= limit;  matchStart ++) {
                      int ch =  target .charAt(  matchStart ) ;
                      if (isEOLChar(ch)) {
                          previousIsEOL = true;
                      } else {
                          if (previousIsEOL) {
                              if (0 <= (matchEnd = this.match(con, this.operations,
                                                              matchStart, 1, this.options)))
                                  break;
                          }
                          previousIsEOL = false;
                      }
                  }
              }
          }
  
          /*
           * Optimization against the first character.
           */
          else if (this.firstChar != null) {
              //System.err.println("DEBUG: with firstchar-matching: "+this.firstChar);
              RangeToken range = this.firstChar;
              for (matchStart = con.start;  matchStart <= limit;  matchStart ++) {
                  int ch =  target .charAt(  matchStart ) ;
                  if (REUtil.isHighSurrogate(ch) && matchStart+1 < con.limit) {
                      ch = REUtil.composeFromSurrogates(ch, target.charAt(matchStart+1));
                  }
                  if (!range.match(ch)) {
                      continue;
                  }
                  if (0 <= (matchEnd = this.match(con, this.operations,
                                                  matchStart, 1, this.options))) {
                          break;
                  }
              }
          }
  
          /*
           * Straightforward matching.
           */
          else {
              for (matchStart = con.start;  matchStart <= limit;  matchStart ++) {
                  if (0 <= (matchEnd = this.match(con, this.operations, matchStart, 1, this.options)))
                      break;
              }
          }
  
          if (matchEnd >= 0) {
              if (con.match != null) {
                  con.match.setBeginning(0, matchStart);
                  con.match.setEnd(0, matchEnd);
              }
              con.setInUse(false);
              return true;
          } else {
              con.setInUse(false);
              return false;
          }
      }
  
      /**
       * @return -1 when not match; offset of the end of matched string when match.
       */
      private int match(Context con, Op op, int offset, int dx, int opts) {
          final ExpressionTarget target = con.target;
          final Stack opStack = new Stack();
          final IntStack dataStack = new IntStack();
          final boolean isSetIgnoreCase = isSet(opts, IGNORE_CASE);
          int retValue = -1;
          boolean returned = false;
  
          for (;;) {
              if (op == null || offset > con.limit || offset < con.start) {
                  if (op == null) {
                      retValue = isSet(opts, XMLSCHEMA_MODE) && offset != con.limit ? -1 : offset;
                  }
                  else {
                     retValue = -1;
                  }
                  returned = true;
              }
              else  {
                  retValue = -1;
                  // dx value is either 1 or -1
                  switch (op.type) {
                  case Op.CHAR:
                      {
                          final int o1 = (dx > 0) ? offset : offset -1;
                          if (o1 >= con.limit || o1 < 0 || !matchChar(op.getData(), target.charAt(o1), isSetIgnoreCase)) {
                              returned = true;
                              break;
                          }
                          offset += dx;
                          op = op.next;
                      }
                      break;
  
                  case Op.DOT:
                      {
                          int o1 = (dx > 0) ? offset : offset - 1;
                          if (o1 >= con.limit || o1 < 0) {
                              returned = true;
                              break;
                          }
                          if (isSet(opts, SINGLE_LINE)) {
                              if (REUtil.isHighSurrogate(target.charAt(o1)) && o1+dx >= 0 && o1+dx < con.limit) {
                                  o1 += dx;
                              }
                          }
                          else {
                              int ch = target.charAt(o1);
                              if (REUtil.isHighSurrogate(ch) && o1+dx >= 0 && o1+dx < con.limit) {
                                  o1 += dx;
                                  ch = REUtil.composeFromSurrogates(ch, target.charAt(o1));
                              }
                              if (isEOLChar(ch)) {
                                  returned = true;
                                  break;
                              }
                          }
                          offset = (dx > 0) ? o1 + 1 : o1;
                          op = op.next;
                      }
                      break;
  
                  case Op.RANGE:
                  case Op.NRANGE:
                      {
                          int o1 = (dx > 0) ? offset : offset -1;
                          if (o1 >= con.limit || o1 < 0) {
                              returned = true;
                              break;
                          }
                          int ch = target.charAt(offset);
                          if (REUtil.isHighSurrogate(ch) && o1+dx < con.limit && o1+dx >=0) {
                              o1 += dx;
                              ch = REUtil.composeFromSurrogates(ch, target.charAt(o1));
                          }
                          final RangeToken tok = op.getToken();
                          if (!tok.match(ch)) {
                              returned = true;
                              break;
                          }
                          offset = (dx > 0) ? o1+1 : o1;
                          op = op.next;
                      }
                      break;
  
                  case Op.ANCHOR:
                      {
                          if (!matchAnchor(target, op, con, offset, opts)) {
                              returned = true;
                              break;
                          }
                          op = op.next;
                      }
                      break;
  
                  case Op.BACKREFERENCE:
                      {
                          int refno = op.getData();
                          if (refno <= 0 || refno >= this.nofparen) {
                              throw new RuntimeException("Internal Error: Reference number must be more than zero: "+refno);
                          }
                          if (con.match.getBeginning(refno) < 0 || con.match.getEnd(refno) < 0) {
                              returned = true;
                              break;
                          }
                          int o2 = con.match.getBeginning(refno);
                          int literallen = con.match.getEnd(refno)-o2;
                          if (dx > 0) {
                              if (!target.regionMatches(isSetIgnoreCase, offset, con.limit, o2, literallen)) {
                                  returned = true;
                                  break;
                              }
                              offset += literallen;
                          }
                          else {
                              if (!target.regionMatches(isSetIgnoreCase, offset-literallen, con.limit, o2, literallen)) {
                                  returned = true;
                                  break;
                              }
                              offset -= literallen;
                          }
                          op = op.next;
                      }
                      break;
  
                  case Op.STRING:
                      {
                          String literal = op.getString();
                          int literallen = literal.length();
                          if (dx > 0) {
                              if (!target.regionMatches(isSetIgnoreCase, offset, con.limit, literal, literallen)) {
                                  returned = true;
                                  break;
                              }
                              offset += literallen;
                          }
                          else {
                              if (!target.regionMatches(isSetIgnoreCase, offset-literallen, con.limit, literal, literallen)) {
                                  returned = true;
                                  break;
                              }
                              offset -= literallen;
                          }
                          op = op.next;
                      }
                      break;
  
                  case Op.CLOSURE:
                      {
                          // Saves current position to avoid zero-width repeats.
                          final int id = op.getData();
                          if (con.closureContexts[id].contains(offset)) {
                              returned = true;
                              break;
                          }
  
                          con.closureContexts[id].addOffset(offset);
                      }
                      // fall through
  
                  case Op.QUESTION:
                      {
                          opStack.push(op);
                          dataStack.push(offset);
                          op = op.getChild();
                      }
                      break;
  
                  case Op.NONGREEDYCLOSURE:
                  case Op.NONGREEDYQUESTION:
                      {
                          opStack.push(op);
                          dataStack.push(offset);
                          op = op.next;
                      }
                      break;
  
                  case Op.UNION:
                      if (op.size() == 0) {
                          returned = true;
                      }
                      else {
                          opStack.push(op);
                          dataStack.push(0);
                          dataStack.push(offset);
                          op = op.elementAt(0);
                      }
                      break;
  
                  case Op.CAPTURE:
                      {
                          final int refno = op.getData();
                          if (con.match != null) {
                              if (refno > 0) {
                                  dataStack.push(con.match.getBeginning(refno));
                                  con.match.setBeginning(refno, offset);
                              }
                              else {
                                  final int index = -refno;
                                  dataStack.push(con.match.getEnd(index));
                                  con.match.setEnd(index, offset);
                              }
                              opStack.push(op);
                              dataStack.push(offset);
                          }
                          op = op.next;
                      }
                      break;
  
                  case Op.LOOKAHEAD:
                  case Op.NEGATIVELOOKAHEAD:
                  case Op.LOOKBEHIND:
                  case Op.NEGATIVELOOKBEHIND:
                      {
                          opStack.push(op);
                          dataStack.push(dx);
                          dataStack.push(offset);
                          dx = (op.type == Op.LOOKAHEAD || op.type == Op.NEGATIVELOOKAHEAD) ? 1 : -1;
                          op = op.getChild();
                      }
                      break;
  
                  case Op.INDEPENDENT:
                      {
                          opStack.push(op);
                          dataStack.push(offset);
                          op = op.getChild();
                      }
                      break;
  
                  case Op.MODIFIER:
                      {
                          int localopts = opts;
                          localopts |= op.getData();
                          localopts &= ~op.getData2();
                          opStack.push(op);
                          dataStack.push(opts);
                          dataStack.push(offset);
                          opts = localopts;
                          op = op.getChild();
                      }
                      break;
  
                  case Op.CONDITION:
                      {
                          Op.ConditionOp cop = (Op.ConditionOp)op;
                          if (cop.refNumber > 0) {
                              if (cop.refNumber >= this.nofparen) {
                                  throw new RuntimeException("Internal Error: Reference number must be more than zero: "+cop.refNumber);
                              }
                              if (con.match.getBeginning(cop.refNumber) >= 0
                                      && con.match.getEnd(cop.refNumber) >= 0) {
                                  op = cop.yes;
                              }
                              else if (cop.no != null) {
                                  op = cop.no;
                              }
                              else {
                                  op = cop.next;
                              }
                          }
                          else {
                              opStack.push(op);
                              dataStack.push(offset);
                              op = cop.condition;
                          }
                      }
                      break;
  
                  default:
                      throw new RuntimeException("Unknown operation type: " + op.type);
                  }
              }
  
              // handle recursive operations
              while (returned) {
                  // exhausted all the operations
                  if (opStack.isEmpty()) {
                      return retValue;
                  }
  
                  op = (Op) opStack.pop();
                  offset = dataStack.pop();
  
                  switch (op.type) {
                  case Op.CLOSURE:
                  case Op.QUESTION:
                      if (retValue < 0) {
                          op = op.next;
                          returned = false;
                      }
                      break;
  
                  case Op.NONGREEDYCLOSURE:
                  case Op.NONGREEDYQUESTION:
                      if (retValue < 0) {
                          op = op.getChild();
                          returned = false;
                      }
                      break;
  
                  case Op.UNION:
                      {
                          int unionIndex = dataStack.pop();
                          if (DEBUG) {
                              System.err.println("UNION: "+unionIndex+", ret="+retValue);
                          }
  
                          if (retValue < 0) {
                              if (++unionIndex < op.size()) {
                                  opStack.push(op);
                                  dataStack.push(unionIndex);
                                  dataStack.push(offset);
                                  op = op.elementAt(unionIndex);
                                  returned = false;
                              }
                              else {
                                  retValue = -1;
                              }
                          }
                      }
                      break;
  
                  case Op.CAPTURE:
                      final int refno = op.getData();
                      final int saved = dataStack.pop();
                      if (retValue < 0) {
                          if (refno > 0) {
                              con.match.setBeginning(refno, saved);
                          }
                          else {
                              con.match.setEnd(-refno, saved);
                          }
                      }
                      break;
  
                  case Op.LOOKAHEAD:
                  case Op.LOOKBEHIND:
                      {
                          dx = dataStack.pop();
                          if (0 <= retValue) {
                              op = op.next;
                              returned = false;
                          }
                          retValue = -1;
                      }
                      break;
  
                  case Op.NEGATIVELOOKAHEAD:
                  case Op.NEGATIVELOOKBEHIND:
                      {
                          dx = dataStack.pop();
                          if (0 > retValue)  {
                              op = op.next;
                              returned = false;
                          }
                          retValue = -1;
                      }
                      break;
  
                  case Op.MODIFIER:
                      opts = dataStack.pop();
                      // fall through
  
                  case Op.INDEPENDENT:
                      if (retValue >= 0)  {
                          offset = retValue;
                          op = op.next;
                          returned = false;
                      }
                      break;
  
                  case Op.CONDITION:
                      {
                          final Op.ConditionOp cop = (Op.ConditionOp)op;
                          if (0 <= retValue) {
                              op = cop.yes;
                          }
                          else if (cop.no != null) {
                              op = cop.no;
                          }
                          else {
                              op = cop.next;
                          }
                      }
                      returned = false;
                      break;
  
                  default:
                      break;
                  }
              }
          }
      }
  
      private boolean matchChar(int ch, int other, boolean ignoreCase) {
          return (ignoreCase) ? matchIgnoreCase(ch, other) : ch == other;
      }
  
      boolean matchAnchor(ExpressionTarget target, Op op, Context con, int offset, int opts) {
          boolean go = false;
          switch (op.getData()) {
          case '^':
              if (isSet(opts, MULTIPLE_LINES)) {
                  if (!(offset == con.start
                        || offset > con.start && offset < con.limit && isEOLChar(target.charAt(offset-1))))
                      return false;
              } else {
                  if (offset != con.start)
                      return false;
              }
              break;
  
          case '@':                         // Internal use only.
              // The @ always matches line beginnings.
              if (!(offset == con.start
                    || offset > con.start && isEOLChar(target.charAt(offset-1))))
                  return false;
              break;
  
          case '$':
              if (isSet(opts, MULTIPLE_LINES)) {
                  if (!(offset == con.limit
                        || offset < con.limit && isEOLChar(target.charAt(offset))))
                      return false;
              } else {
                  if (!(offset == con.limit
                        || offset+1 == con.limit && isEOLChar(target.charAt(offset))
                        || offset+2 == con.limit &&  target.charAt(offset) == CARRIAGE_RETURN
                        &&  target.charAt(offset+1) == LINE_FEED))
                      return false;
              }
              break;
  
          case 'A':
              if (offset != con.start)  return false;
              break;
  
          case 'Z':
              if (!(offset == con.limit
                    || offset+1 == con.limit && isEOLChar(target.charAt(offset))
                    || offset+2 == con.limit &&  target.charAt(offset) == CARRIAGE_RETURN
                    &&  target.charAt(offset+1) == LINE_FEED))
                  return false;
              break;
  
          case 'z':
              if (offset != con.limit)  return false;
              break;
  
          case 'b':
              if (con.length == 0)
                  return false;
              {
                  int after = getWordType(target, con.start, con.limit, offset, opts);
                  if (after == WT_IGNORE)  return false;
                  int before = getPreviousWordType(target, con.start, con.limit, offset, opts);
                  if (after == before)  return false;
              }
              break;
  
          case 'B':
              if (con.length == 0)
                  go = true;
              else {
                  int after = getWordType(target, con.start, con.limit, offset, opts);
                  go = after == WT_IGNORE
                       || after == getPreviousWordType(target, con.start, con.limit, offset, opts);
              }
              if (!go)  return false;
              break;
  
          case '<':
              if (con.length == 0 || offset == con.limit)  return false;
              if (getWordType(target, con.start, con.limit, offset, opts) != WT_LETTER
                  || getPreviousWordType(target, con.start, con.limit, offset, opts) != WT_OTHER)
                  return false;
              break;
  
          case '>':
              if (con.length == 0 || offset == con.start)  return false;
              if (getWordType(target, con.start, con.limit, offset, opts) != WT_OTHER
                  || getPreviousWordType(target, con.start, con.limit, offset, opts) != WT_LETTER)
                  return false;
              break;
          } // switch anchor type
  
          return true;
      }
  
      private static final int getPreviousWordType(ExpressionTarget target, int begin, int end,
                                                   int offset, int opts) {
          int ret = getWordType(target, begin, end, --offset, opts);
          while (ret == WT_IGNORE)
              ret = getWordType(target, begin, end, --offset, opts);
          return ret;
      }
  
      private static final int getWordType(ExpressionTarget target, int begin, int end,
                                           int offset, int opts) {
          if (offset < begin || offset >= end)  return WT_OTHER;
          return getWordType0(target.charAt(offset) , opts);
      }
  
  
      /**
       * Checks whether the <var>target</var> text <strong>contains</strong> this pattern or not.
       *
       * @return true if the target is matched to this regular expression.
       */
      public boolean matches(CharacterIterator target) {
          return this.matches(target, (Match)null);
      }
  
  
      /**
       * Checks whether the <var>target</var> text <strong>contains</strong> this pattern or not.
       *
       * @param match A Match instance for storing matching result.
       * @return Offset of the start position in <VAR>target</VAR>; or -1 if not match.
       */
      public boolean matches(CharacterIterator  target, Match match) {
          int start = target.getBeginIndex();
          int end = target.getEndIndex();
  
  
  
          synchronized (this) {
              if (this.operations == null)
                  this.prepare();
              if (this.context == null)
                  this.context = new Context();
          }
          Context con = null;
          synchronized (this.context) {
              con = this.context.inuse ? new Context() : this.context;
              con.reset(target, start, end, this.numberOfClosures);
          }
          if (match != null) {
              match.setNumberOfGroups(this.nofparen);
              match.setSource(target);
          } else if (this.hasBackReferences) {
              match = new Match();
              match.setNumberOfGroups(this.nofparen);
              // Need not to call setSource() because
              // a caller can not access this match instance.
          }
          con.match = match;
  
          if (RegularExpression.isSet(this.options, XMLSCHEMA_MODE)) {
              int matchEnd = this.match(con, this.operations, con.start, 1, this.options);
              //System.err.println("DEBUG: matchEnd="+matchEnd);
              if (matchEnd == con.limit) {
                  if (con.match != null) {
                      con.match.setBeginning(0, con.start);
                      con.match.setEnd(0, matchEnd);
                  }
                  con.setInUse(false);
                  return true;
              }
              return false;
          }
  
          /*
           * The pattern has only fixed string.
           * The engine uses Boyer-Moore.
           */
          if (this.fixedStringOnly) {
              //System.err.println("DEBUG: fixed-only: "+this.fixedString);
              int o = this.fixedStringTable.matches(target, con.start, con.limit);
              if (o >= 0) {
                  if (con.match != null) {
                      con.match.setBeginning(0, o);
                      con.match.setEnd(0, o+this.fixedString.length());
                  }
                  con.setInUse(false);
                  return true;
              }
              con.setInUse(false);
              return false;
          }
  
          /*
           * The pattern contains a fixed string.
           * The engine checks with Boyer-Moore whether the text contains the fixed string or not.
           * If not, it return with false.
           */
          if (this.fixedString != null) {
              int o = this.fixedStringTable.matches(target, con.start, con.limit);
              if (o < 0) {
                  //System.err.println("Non-match in fixed-string search.");
                  con.setInUse(false);
                  return false;
              }
          }
  
          int limit = con.limit-this.minlength;
          int matchStart;
          int matchEnd = -1;
  
          /*
           * Checks whether the expression starts with ".*".
           */
          if (this.operations != null
              && this.operations.type == Op.CLOSURE && this.operations.getChild().type == Op.DOT) {
              if (isSet(this.options, SINGLE_LINE)) {
                  matchStart = con.start;
                  matchEnd = this.match(con, this.operations, con.start, 1, this.options);
              } else {
                  boolean previousIsEOL = true;
                  for (matchStart = con.start;  matchStart <= limit;  matchStart ++) {
                      int ch =  target .setIndex(  matchStart ) ;
                      if (isEOLChar(ch)) {
                          previousIsEOL = true;
                      } else {
                          if (previousIsEOL) {
                              if (0 <= (matchEnd = this.match(con, this.operations,
                                                              matchStart, 1, this.options)))
                                  break;
                          }
                          previousIsEOL = false;
                      }
                  }
              }
          }
  
          /*
           * Optimization against the first character.
           */
          else if (this.firstChar != null) {
              //System.err.println("DEBUG: with firstchar-matching: "+this.firstChar);
              RangeToken range = this.firstChar;
              for (matchStart = con.start;  matchStart <= limit;  matchStart ++) {
                  int ch =  target .setIndex(  matchStart ) ;
                  if (REUtil.isHighSurrogate(ch) && matchStart+1 < con.limit) {
                      ch = REUtil.composeFromSurrogates(ch, target.setIndex(matchStart+1));
                  }
                  if (!range.match(ch)) {
                      continue;
                  }
                  if (0 <= (matchEnd = this.match(con, this.operations,
                                                  matchStart, 1, this.options))) {
                      break;
                  }
              }
          }
  
          /*
           * Straightforward matching.
           */
          else {
              for (matchStart = con.start;  matchStart <= limit;  matchStart ++) {
                  if (0 <= (matchEnd = this. match(con, this.operations, matchStart, 1, this.options)))
                      break;
              }
          }
  
          if (matchEnd >= 0) {
              if (con.match != null) {
                  con.match.setBeginning(0, matchStart);
                  con.match.setEnd(0, matchEnd);
              }
              con.setInUse(false);
              return true;
          } else {
              con.setInUse(false);
              return false;
          }
      }
  
      // ================================================================
  
      /**
       * A regular expression.
       * @serial
       */
      String regex;
      /**
       * @serial
       */
      int options;
  
      /**
       * The number of parenthesis in the regular expression.
       * @serial
       */
      int nofparen;
      /**
       * Internal representation of the regular expression.
       * @serial
       */
      Token tokentree;
  
      boolean hasBackReferences = false;
  
      transient int minlength;
      transient Op operations = null;
      transient int numberOfClosures;
      transient Context context = null;
      transient RangeToken firstChar = null;
  
      transient String fixedString = null;
      transient int fixedStringOptions;
      transient BMPattern fixedStringTable = null;
      transient boolean fixedStringOnly = false;
  
      static abstract class ExpressionTarget {
          abstract char charAt(int index);
          abstract boolean regionMatches(boolean ignoreCase, int offset, int limit, String part, int partlen);
          abstract boolean regionMatches(boolean ignoreCase, int offset, int limit, int offset2, int partlen);
      }
  
      static final class StringTarget extends ExpressionTarget {
  
          private String target;
  
          StringTarget(String target) {
              this.target = target;
          }
  
          final void resetTarget(String target) {
              this.target = target;
          }
  
          final char charAt(int index) {
              return target.charAt(index);
          }
  
          final boolean regionMatches(boolean ignoreCase, int offset, int limit,
                                String part, int partlen) {
              if (limit-offset < partlen) {
                  return false;
              }
              return (ignoreCase) ? target.regionMatches(true, offset, part, 0, partlen) : target.regionMatches(offset, part, 0, partlen);
          }
  
          final boolean regionMatches(boolean ignoreCase, int offset, int limit,
                                      int offset2, int partlen) {
              if (limit-offset < partlen) {
                  return false;
              }
              return (ignoreCase) ? target.regionMatches(true, offset, target, offset2, partlen)
                                  : target.regionMatches(offset, target, offset2, partlen);
          }
      }
  
      static final class CharArrayTarget extends ExpressionTarget {
  
          char[] target;
  
          CharArrayTarget(char[] target) {
              this.target = target;
          }
  
          final void resetTarget(char[] target) {
              this.target = target;
          }
  
          char charAt(int index) {
              return target[index];
          }
  
          final boolean regionMatches(boolean ignoreCase, int offset, int limit,
                  String part, int partlen) {
              if (offset < 0 || limit-offset < partlen)  {
                  return false;
              }
              return (ignoreCase) ? regionMatchesIgnoreCase(offset, limit, part, partlen)
                                  : regionMatches(offset, limit, part, partlen);
          }
  
          private final boolean regionMatches(int offset, int limit, String part, int partlen) {
              int i = 0;
              while (partlen-- > 0) {
                  if (target[offset++] != part.charAt(i++)) {
                      return false;
                  }
              }
              return true;
          }
  
          private final boolean regionMatchesIgnoreCase(int offset, int limit, String part, int partlen) {
              int i = 0;
              while (partlen-- > 0) {
                  final char ch1 = target[offset++] ;
                  final char ch2 = part.charAt(i++);
                  if (ch1 == ch2) {
                      continue;
                  }
                  final char uch1 = Character.toUpperCase(ch1);
                  final char uch2 = Character.toUpperCase(ch2);
                  if (uch1 == uch2) {
                      continue;
                  }
                  if (Character.toLowerCase(uch1) != Character.toLowerCase(uch2)) {
                      return false;
                  }
              }
              return true;
          }
  
          final boolean regionMatches(boolean ignoreCase, int offset, int limit, int offset2, int partlen) {
              if (offset < 0 || limit-offset < partlen) {
                  return false;
              }
              return (ignoreCase) ? regionMatchesIgnoreCase(offset, limit, offset2, partlen)
                                  : regionMatches(offset, limit, offset2, partlen);
          }
  
          private final boolean regionMatches(int offset, int limit, int offset2, int partlen) {
              int i = offset2;
              while (partlen-- > 0) {
                  if ( target [  offset++ ]  !=  target [  i++ ] )
                      return false;
              }
              return true;
          }
  
          private final boolean regionMatchesIgnoreCase(int offset, int limit, int offset2, int partlen) {
              int i = offset2;
              while (partlen-- > 0) {
                  final char ch1 =  target[offset++] ;
                  final char ch2 =  target[i++] ;
                  if (ch1 == ch2) {
                      continue;
                  }
                  final char uch1 = Character.toUpperCase(ch1);
                  final char uch2 = Character.toUpperCase(ch2);
                  if (uch1 == uch2) {
                      continue;
                  }
                  if (Character.toLowerCase(uch1) != Character.toLowerCase(uch2)) {
                      return false;
                  }
              }
              return true;
          }
      }
  
      static final class CharacterIteratorTarget extends ExpressionTarget {
          CharacterIterator target;
  
          CharacterIteratorTarget(CharacterIterator target) {
              this.target = target;
          }
  
          final void resetTarget(CharacterIterator target) {
              this.target = target;
          }
  
          final char charAt(int index) {
              return target.setIndex(index);
          }
  
          final boolean regionMatches(boolean ignoreCase, int offset, int limit,
                  String part, int partlen) {
              if (offset < 0 || limit-offset < partlen)  {
                  return false;
              }
              return (ignoreCase) ? regionMatchesIgnoreCase(offset, limit, part, partlen)
                                  : regionMatches(offset, limit, part, partlen);
          }
  
          private final boolean regionMatches(int offset, int limit, String part, int partlen) {
              int i = 0;
              while (partlen-- > 0) {
                  if (target.setIndex(offset++) != part.charAt(i++)) {
                      return false;
                  }
              }
              return true;
          }
  
          private final boolean regionMatchesIgnoreCase(int offset, int limit, String part, int partlen) {
              int i = 0;
              while (partlen-- > 0) {
                  final char ch1 = target.setIndex(offset++) ;
                  final char ch2 = part.charAt(i++);
                  if (ch1 == ch2) {
                      continue;
                  }
                  final char uch1 = Character.toUpperCase(ch1);
                  final char uch2 = Character.toUpperCase(ch2);
                  if (uch1 == uch2) {
                      continue;
                  }
                  if (Character.toLowerCase(uch1) != Character.toLowerCase(uch2)) {
                      return false;
                  }
              }
              return true;
          }
  
          final boolean regionMatches(boolean ignoreCase, int offset, int limit, int offset2, int partlen) {
              if (offset < 0 || limit-offset < partlen) {
                  return false;
              }
              return (ignoreCase) ? regionMatchesIgnoreCase(offset, limit, offset2, partlen)
                                  : regionMatches(offset, limit, offset2, partlen);
          }
  
          private final boolean regionMatches(int offset, int limit, int offset2, int partlen) {
              int i = offset2;
              while (partlen-- > 0) {
                  if (target.setIndex(offset++) != target.setIndex(i++)) {
                      return false;
                  }
              }
              return true;
          }
  
          private final boolean regionMatchesIgnoreCase(int offset, int limit, int offset2, int partlen) {
              int i = offset2;
              while (partlen-- > 0) {
                  final char ch1 = target.setIndex(offset++) ;
                  final char ch2 = target.setIndex(i++) ;
                  if (ch1 == ch2) {
                      continue;
                  }
                  final char uch1 = Character.toUpperCase(ch1);
                  final char uch2 = Character.toUpperCase(ch2);
                  if (uch1 == uch2) {
                      continue;
                  }
                  if (Character.toLowerCase(uch1) != Character.toLowerCase(uch2)) {
                      return false;
                  }
              }
              return true;
          }
      }
  
      static final class ClosureContext {
  
          int[] offsets = new int[4];
          int currentIndex = 0;
  
          boolean contains(int offset) {
              for (int i=0; i<currentIndex;++i) {
                  if (offsets[i] == offset) {
                      return true;
                  }
              }
              return false;
          }
  
          void reset() {
              currentIndex = 0;
          }
  
          void addOffset(int offset) {
              // We do not check for duplicates, caller is responsible for that
              if (currentIndex == offsets.length) {
                  offsets = expandOffsets();
              }
              offsets[currentIndex++] = offset;
          }
  
          private int[] expandOffsets() {
              final int len = offsets.length;
              final int newLen = len << 1;
              int[] newOffsets = new int[newLen];
  
              System.arraycopy(offsets, 0, newOffsets, 0, currentIndex);
              return newOffsets;
          }
      }
  
      static final class Context {
          int start;
          int limit;
          int length;
          Match match;
          boolean inuse = false;
          ClosureContext[] closureContexts;
  
          private StringTarget stringTarget;
          private CharArrayTarget charArrayTarget;
          private CharacterIteratorTarget characterIteratorTarget;
  
          ExpressionTarget target;
  
          Context() {
          }
  
          private void resetCommon(int nofclosures) {
              this.length = this.limit-this.start;
              setInUse(true);
              this.match = null;
              if (this.closureContexts == null || this.closureContexts.length != nofclosures) {
                  this.closureContexts = new ClosureContext[nofclosures];
              }
              for (int i = 0;  i < nofclosures;  i ++)  {
                  if (this.closureContexts[i] == null) {
                      this.closureContexts[i] = new ClosureContext();
                  }
                  else {
                      this.closureContexts[i].reset();
                  }
              }
          }
  
          void reset(CharacterIterator target, int start, int limit, int nofclosures) {
              if (characterIteratorTarget == null) {
                  characterIteratorTarget = new CharacterIteratorTarget(target);
              }
              else {
                  characterIteratorTarget.resetTarget(target);
              }
              this.target = characterIteratorTarget;
              this.start = start;
              this.limit = limit;
              this.resetCommon(nofclosures);
          }
  
          void reset(String target, int start, int limit, int nofclosures) {
              if (stringTarget == null) {
                  stringTarget = new StringTarget(target);
              }
              else {
                  stringTarget.resetTarget(target);
              }
              this.target = stringTarget;
              this.start = start;
              this.limit = limit;
              this.resetCommon(nofclosures);
          }
  
          void reset(char[] target, int start, int limit, int nofclosures) {
              if (charArrayTarget == null) {
                  charArrayTarget = new CharArrayTarget(target);
              }
              else {
                  charArrayTarget.resetTarget(target);
              }
              this.target = charArrayTarget;
              this.start = start;
              this.limit = limit;
              this.resetCommon(nofclosures);
          }
          synchronized void setInUse(boolean inUse) {
              this.inuse = inUse;
          }
      }
  
      /**
       * Prepares for matching.  This method is called just before starting matching.
       */
      void prepare() {
          if (Op.COUNT)  Op.nofinstances = 0;
          this.compile(this.tokentree);
          /*
          if  (this.operations.type == Op.CLOSURE && this.operations.getChild().type == Op.DOT) { // .*
              Op anchor = Op.createAnchor(isSet(this.options, SINGLE_LINE) ? 'A' : '@');
              anchor.next = this.operations;
              this.operations = anchor;
          }
          */
          if (Op.COUNT)  System.err.println("DEBUG: The number of operations: "+Op.nofinstances);
  
          this.minlength = this.tokentree.getMinLength();
  
          this.firstChar = null;
          if (!isSet(this.options, PROHIBIT_HEAD_CHARACTER_OPTIMIZATION)
              && !isSet(this.options, XMLSCHEMA_MODE)) {
              RangeToken firstChar = Token.createRange();
              int fresult = this.tokentree.analyzeFirstCharacter(firstChar, this.options);
              if (fresult == Token.FC_TERMINAL) {
                  firstChar.compactRanges();
                  this.firstChar = firstChar;
                  if (DEBUG)
                      System.err.println("DEBUG: Use the first character optimization: "+firstChar);
              }
          }
  
          if (this.operations != null
              && (this.operations.type == Op.STRING || this.operations.type == Op.CHAR)
              && this.operations.next == null) {
              if (DEBUG)
                  System.err.print(" *** Only fixed string! *** ");
              this.fixedStringOnly = true;
              if (this.operations.type == Op.STRING)
                  this.fixedString = this.operations.getString();
              else if (this.operations.getData() >= 0x10000) { // Op.CHAR
                  this.fixedString = REUtil.decomposeToSurrogates(this.operations.getData());
              } else {
                  char[] ac = new char[1];
                  ac[0] = (char)this.operations.getData();
                  this.fixedString = new String(ac);
              }
              this.fixedStringOptions = this.options;
              this.fixedStringTable = new BMPattern(this.fixedString, 256,
                                                    isSet(this.fixedStringOptions, IGNORE_CASE));
          } else if (!isSet(this.options, PROHIBIT_FIXED_STRING_OPTIMIZATION)
                     && !isSet(this.options, XMLSCHEMA_MODE)) {
              Token.FixedStringContainer container = new Token.FixedStringContainer();
              this.tokentree.findFixedString(container, this.options);
              this.fixedString = container.token == null ? null : container.token.getString();
              this.fixedStringOptions = container.options;
              if (this.fixedString != null && this.fixedString.length() < 2)
                  this.fixedString = null;
              // This pattern has a fixed string of which length is more than one.
              if (this.fixedString != null) {
                  this.fixedStringTable = new BMPattern(this.fixedString, 256,
                                                        isSet(this.fixedStringOptions, IGNORE_CASE));
                  if (DEBUG) {
                      System.err.println("DEBUG: The longest fixed string: "+this.fixedString.length()
                                         +"/" //+this.fixedString
                                         +"/"+REUtil.createOptionString(this.fixedStringOptions));
                      System.err.print("String: ");
                      REUtil.dumpString(this.fixedString);
                  }
              }
          }
      }
  
      /**
       * An option.
       * If you specify this option, <span class="REGEX"><kbd>(</kbd><var>X</var><kbd>)</kbd></span>
       * captures matched text, and <span class="REGEX"><kbd>(:?</kbd><var>X</var><kbd>)</kbd></span>
       * does not capture.
       *
       * @see #RegularExpression(java.lang.String,int)
       * @see #setPattern(java.lang.String,int)
      static final int MARK_PARENS = 1<<0;
       */
  
      /**
       * "i"
       */
      static final int IGNORE_CASE = 1<<1;
  
      /**
       * "s"
       */
      static final int SINGLE_LINE = 1<<2;
  
      /**
       * "m"
       */
      static final int MULTIPLE_LINES = 1<<3;
  
      /**
       * "x"
       */
      static final int EXTENDED_COMMENT = 1<<4;
  
      /**
       * This option redefines <span class="REGEX"><kbd>\d \D \w \W \s \S</kbd></span>.
       *
       * @see #RegularExpression(java.lang.String,int)
       * @see #setPattern(java.lang.String,int)
       * @see #UNICODE_WORD_BOUNDARY
       */
      static final int USE_UNICODE_CATEGORY = 1<<5; // "u"
  
      /**
       * An option.
       * This enables to process locale-independent word boundary for <span class="REGEX"><kbd>\b \B \&lt; \></kbd></span>.
       * <p>By default, the engine considers a position between a word character
       * (<span class="REGEX"><Kbd>\w</kbd></span>) and a non word character
       * is a word boundary.
       * <p>By this option, the engine checks word boundaries with the method of
       * 'Unicode Regular Expression Guidelines' Revision 4.
       *
       * @see #RegularExpression(java.lang.String,int)
       * @see #setPattern(java.lang.String,int)
       */
      static final int UNICODE_WORD_BOUNDARY = 1<<6; // "w"
  
      /**
       * "H"
       */
      static final int PROHIBIT_HEAD_CHARACTER_OPTIMIZATION = 1<<7;
      /**
       * "F"
       */
      static final int PROHIBIT_FIXED_STRING_OPTIMIZATION = 1<<8;
      /**
       * "X". XML Schema mode.
       */
      static final int XMLSCHEMA_MODE = 1<<9;
      /**
       * ",".
       */
      static final int SPECIAL_COMMA = 1<<10;
  
  
      private static final boolean isSet(int options, int flag) {
          return (options & flag) == flag;
      }
  
      /**
       * Creates a new RegularExpression instance.
       *
       * @param regex A regular expression
       * @exception org.apache.xerces.utils.regex.ParseException <VAR>regex</VAR> is not conforming to the syntax.
       */
      public RegularExpression(String regex) throws ParseException {
          this(regex, null);
      }
  
      /**
       * Creates a new RegularExpression instance with options.
       *
       * @param regex A regular expression
       * @param options A String consisted of "i" "m" "s" "u" "w" "," "X"
       * @exception org.apache.xerces.utils.regex.ParseException <VAR>regex</VAR> is not conforming to the syntax.
       */
      public RegularExpression(String regex, String options) throws ParseException {
          this.setPattern(regex, options);
      }
  
      /**
       * Creates a new RegularExpression instance with options.
       *
       * @param regex A regular expression
       * @param options A String consisted of "i" "m" "s" "u" "w" "," "X"
       * @exception org.apache.xerces.utils.regex.ParseException <VAR>regex</VAR> is not conforming to the syntax.
       */
      public RegularExpression(String regex, String options, Locale locale) throws ParseException {
          this.setPattern(regex, options, locale);
      }
  
      RegularExpression(String regex, Token tok, int parens, boolean hasBackReferences, int options) {
          this.regex = regex;
          this.tokentree = tok;
          this.nofparen = parens;
          this.options = options;
          this.hasBackReferences = hasBackReferences;
      }
  
      /**
       *
       */
      public void setPattern(String newPattern) throws ParseException {
          this.setPattern(newPattern, Locale.getDefault());
      }
  
      public void setPattern(String newPattern, Locale locale) throws ParseException {
          this.setPattern(newPattern, this.options, locale);
      }
  
      private void setPattern(String newPattern, int options, Locale locale) throws ParseException {
          this.regex = newPattern;
          this.options = options;
          RegexParser rp = RegularExpression.isSet(this.options, RegularExpression.XMLSCHEMA_MODE)
                           ? new ParserForXMLSchema(locale) : new RegexParser(locale);
          this.tokentree = rp.parse(this.regex, this.options);
          this.nofparen = rp.parennumber;
          this.hasBackReferences = rp.hasBackReferences;
  
          this.operations = null;
          this.context = null;
      }
      /**
       *
       */
      public void setPattern(String newPattern, String options) throws ParseException {
          this.setPattern(newPattern, options, Locale.getDefault());
      }
  
      public void setPattern(String newPattern, String options, Locale locale) throws ParseException {
          this.setPattern(newPattern, REUtil.parseOptions(options), locale);
      }
  
      /**
       *
       */
      public String getPattern() {
          return this.regex;
      }
  
      /**
       * Represents this instence in String.
       */
      public String toString() {
          return this.tokentree.toString(this.options);
      }
  
      /**
       * Returns a option string.
       * The order of letters in it may be different from a string specified
       * in a constructor or <code>setPattern()</code>.
       *
       * @see #RegularExpression(java.lang.String,java.lang.String)
       * @see #setPattern(java.lang.String,java.lang.String)
       */
      public String getOptions() {
          return REUtil.createOptionString(this.options);
      }
  
      /**
       *  Return true if patterns are the same and the options are equivalent.
       */
      public boolean equals(Object obj) {
          if (obj == null)  return false;
          if (!(obj instanceof RegularExpression))
              return false;
          RegularExpression r = (RegularExpression)obj;
          return this.regex.equals(r.regex) && this.options == r.options;
      }
  
      boolean equals(String pattern, int options) {
          return this.regex.equals(pattern) && this.options == options;
      }
  
      /**
       *
       */
      public int hashCode() {
          return (this.regex+"/"+this.getOptions()).hashCode();
      }
  
      /**
       * Return the number of regular expression groups.
       * This method returns 1 when the regular expression has no capturing-parenthesis.
       *
       */
      public int getNumberOfGroups() {
          return this.nofparen;
      }
  
      // ================================================================
  
      private static final int WT_IGNORE = 0;
      private static final int WT_LETTER = 1;
      private static final int WT_OTHER = 2;
      private static final int getWordType0(char ch, int opts) {
          if (!isSet(opts, UNICODE_WORD_BOUNDARY)) {
              if (isSet(opts, USE_UNICODE_CATEGORY)) {
                  return (Token.getRange("IsWord", true).match(ch)) ? WT_LETTER : WT_OTHER;
              }
              return isWordChar(ch) ? WT_LETTER : WT_OTHER;
          }
  
          switch (Character.getType(ch)) {
          case Character.UPPERCASE_LETTER:      // L
          case Character.LOWERCASE_LETTER:      // L
          case Character.TITLECASE_LETTER:      // L
          case Character.MODIFIER_LETTER:       // L
          case Character.OTHER_LETTER:          // L
          case Character.LETTER_NUMBER:         // N
          case Character.DECIMAL_DIGIT_NUMBER:  // N
          case Character.OTHER_NUMBER:          // N
          case Character.COMBINING_SPACING_MARK: // Mc
              return WT_LETTER;
  
          case Character.FORMAT:                // Cf
          case Character.NON_SPACING_MARK:      // Mn
          case Character.ENCLOSING_MARK:        // Mc
              return WT_IGNORE;
  
          case Character.CONTROL:               // Cc
              switch (ch) {
              case '\t':
              case '\n':
              case '\u000B':
              case '\f':
              case '\r':
                  return WT_OTHER;
              default:
                  return WT_IGNORE;
              }
  
          default:
              return WT_OTHER;
          }
      }
  
      // ================================================================
  
      static final int LINE_FEED = 0x000A;
      static final int CARRIAGE_RETURN = 0x000D;
      static final int LINE_SEPARATOR = 0x2028;
      static final int PARAGRAPH_SEPARATOR = 0x2029;
  
      private static final boolean isEOLChar(int ch) {
          return ch == LINE_FEED || ch == CARRIAGE_RETURN || ch == LINE_SEPARATOR
          || ch == PARAGRAPH_SEPARATOR;
      }
  
      private static final boolean isWordChar(int ch) { // Legacy word characters
          if (ch == '_')  return true;
          if (ch < '0')  return false;
          if (ch > 'z')  return false;
          if (ch <= '9')  return true;
          if (ch < 'A')  return false;
          if (ch <= 'Z')  return true;
          if (ch < 'a')  return false;
          return true;
      }
  
      private static final boolean matchIgnoreCase(int chardata, int ch) {
          if (chardata == ch)  return true;
          if (chardata > 0xffff || ch > 0xffff)  return false;
          char uch1 = Character.toUpperCase((char)chardata);
          char uch2 = Character.toUpperCase((char)ch);
          if (uch1 == uch2)  return true;
          return Character.toLowerCase(uch1) == Character.toLowerCase(uch2);
      }
  }
  