489 lines
20 KiB
C++
489 lines
20 KiB
C++
/*
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* Copyright (C) {1999-2001}, International Business Machines Corporation and others. All Rights Reserved.
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**********************************************************************
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* Date Name Description
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* 10/22/99 alan Creation.
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* 11/11/99 rgillam Complete port from Java.
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**********************************************************************
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*/
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#ifndef RBBI_H
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#define RBBI_H
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#include "unicode/utypes.h"
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#include "unicode/brkiter.h"
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#include "unicode/udata.h"
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U_NAMESPACE_BEGIN
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class RuleBasedBreakIteratorTables;
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class BreakIterator;
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/**
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* <p>A subclass of BreakIterator whose behavior is specified using a list of rules.</p>
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*
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* <p>There are two kinds of rules, which are separated by semicolons: <i>substitutions</i>
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* and <i>regular expressions.</i></p>
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*
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* <p>A substitution rule defines a name that can be used in place of an expression. It
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* consists of a name, which is a string of characters contained in angle brackets, an equals
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* sign, and an expression. (There can be no whitespace on either side of the equals sign.)
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* To keep its syntactic meaning intact, the expression must be enclosed in parentheses or
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* square brackets. A substitution is visible after its definition, and is filled in using
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* simple textual substitution. Substitution definitions can contain other substitutions, as
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* long as those substitutions have been defined first. Substitutions are generally used to
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* make the regular expressions (which can get quite complex) shorted and easier to read.
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* They typically define either character categories or commonly-used subexpressions.</p>
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*
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* <p>There is one special substitution. If the description defines a substitution
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* called "<ignore>", the expression must be a [] expression, and the
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* expression defines a set of characters (the "<em>ignore characters</em>") that
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* will be transparent to the BreakIterator. A sequence of characters will break the
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* same way it would if any ignore characters it contains are taken out. Break
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* positions never occur befoer ignore characters.</p>
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*
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* <p>A regular expression uses a subset of the normal Unix regular-expression syntax, and
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* defines a sequence of characters to be kept together. With one significant exception, the
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* iterator uses a longest-possible-match algorithm when matching text to regular
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* expressions. The iterator also treats descriptions containing multiple regular expressions
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* as if they were ORed together (i.e., as if they were separated by |).</p>
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*
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* <p>The special characters recognized by the regular-expression parser are as follows:</p>
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*
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* <blockquote>
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* <table border="1" width="100%">
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* <tr>
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* <td width="6%">*</td>
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* <td width="94%">Specifies that the expression preceding the asterisk may occur any number
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* of times (including not at all).</td>
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* </tr>
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* <tr>
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* <td width="6%">{}</td>
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* <td width="94%">Encloses a sequence of characters that is optional.</td>
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* </tr>
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* <tr>
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* <td width="6%">()</td>
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* <td width="94%">Encloses a sequence of characters. If followed by *, the sequence
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* repeats. Otherwise, the parentheses are just a grouping device and a way to delimit
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* the ends of expressions containing |.</td>
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* </tr>
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* <tr>
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* <td width="6%">|</td>
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* <td width="94%">Separates two alternative sequences of characters. Either one
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* sequence or the other, but not both, matches this expression. The | character can
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* only occur inside ().</td>
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* </tr>
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* <tr>
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* <td width="6%">.</td>
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* <td width="94%">Matches any character.</td>
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* </tr>
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* <tr>
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* <td width="6%">*?</td>
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* <td width="94%">Specifies a non-greedy asterisk. *? works the same way as *, except
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* when there is overlap between the last group of characters in the expression preceding the
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* * and the first group of characters following the *. When there is this kind of
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* overlap, * will match the longest sequence of characters that match the expression before
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* the *, and *? will match the shortest sequence of characters matching the expression
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* before the *?. For example, if you have "xxyxyyyxyxyxxyxyxyy" in the text,
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* "x[xy]*x" will match through to the last x (i.e., "<strong>xxyxyyyxyxyxxyxyx</strong>yy",
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* but "x[xy]*?x" will only match the first two xes ("<strong>xx</strong>yxyyyxyxyxxyxyxyy").</td>
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* </tr>
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* <tr>
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* <td width="6%">[]</td>
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* <td width="94%">Specifies a group of alternative characters. A [] expression will
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* match any single character that is specified in the [] expression. For more on the
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* syntax of [] expressions, see below.</td>
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* </tr>
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* <tr>
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* <td width="6%">/</td>
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* <td width="94%">Specifies where the break position should go if text matches this
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* expression. (e.g., "[a-z]*/[:Zs:]*1" will match if the iterator sees a run
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* of letters, followed by a run of whitespace, followed by a digit, but the break position
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* will actually go before the whitespace). Expressions that don't contain / put the
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* break position at the end of the matching text.</td>
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* </tr>
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* <tr>
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* <td width="6%">\</td>
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* <td width="94%">Escape character. The \ itself is ignored, but causes the next
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* character to be treated as literal character. This has no effect for many
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* characters, but for the characters listed above, this deprives them of their special
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* meaning. (There are no special escape sequences for Unicode characters, or tabs and
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* newlines; these are all handled by a higher-level protocol. In a Java string,
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* "\n" will be converted to a literal newline character by the time the
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* regular-expression parser sees it. Of course, this means that \ sequences that are
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* visible to the regexp parser must be written as \\ when inside a Java string.) All
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* characters in the ASCII range except for letters, digits, and control characters are
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* reserved characters to the parser and must be preceded by \ even if they currently don't
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* mean anything.</td>
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* </tr>
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* <tr>
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* <td width="6%">!</td>
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* <td width="94%">If ! appears at the beginning of a regular expression, it tells the regexp
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* parser that this expression specifies the backwards-iteration behavior of the iterator,
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* and not its normal iteration behavior. This is generally only used in situations
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* where the automatically-generated backwards-iteration brhavior doesn't produce
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* satisfactory results and must be supplemented with extra client-specified rules.</td>
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* </tr>
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* <tr>
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* <td width="6%"><em>(all others)</em></td>
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* <td width="94%">All other characters are treated as literal characters, which must match
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* the corresponding character(s) in the text exactly.</td>
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* </tr>
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* </table>
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* </blockquote>
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*
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* <p>Within a [] expression, a number of other special characters can be used to specify
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* groups of characters:</p>
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*
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* <blockquote>
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* <table border="1" width="100%">
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* <tr>
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* <td width="6%">-</td>
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* <td width="94%">Specifies a range of matching characters. For example
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* "[a-p]" matches all lowercase Latin letters from a to p (inclusive). The -
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* sign specifies ranges of continuous Unicode numeric values, not ranges of characters in a
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* language's alphabetical order: "[a-z]" doesn't include capital letters, nor does
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* it include accented letters such as a-umlaut.</td>
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* </tr>
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* <tr>
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* <td width="6%">::</td>
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* <td width="94%">A pair of colons containing a one- or two-letter code matches all
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* characters in the corresponding Unicode category. The two-letter codes are the same
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* as the two-letter codes in the Unicode database (for example, "[:Sc::Sm:]"
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* matches all currency symbols and all math symbols). Specifying a one-letter code is
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* the same as specifying all two-letter codes that begin with that letter (for example,
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* "[:L:]" matches all letters, and is equivalent to
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* "[:Lu::Ll::Lo::Lm::Lt:]"). Anything other than a valid two-letter Unicode
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* category code or a single letter that begins a Unicode category code is illegal within
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* colons.</td>
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* </tr>
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* <tr>
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* <td width="6%">[]</td>
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* <td width="94%">[] expressions can nest. This has no effect, except when used in
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* conjunction with the ^ token.</td>
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* </tr>
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* <tr>
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* <td width="6%">^</td>
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* <td width="94%">Excludes the character (or the characters in the [] expression) following
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* it from the group of characters. For example, "[a-z^p]" matches all Latin
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* lowercase letters except p. "[:L:^[\u4e00-\u9fff]]" matches all letters
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* except the Han ideographs.</td>
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* </tr>
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* <tr>
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* <td width="6%"><em>(all others)</em></td>
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* <td width="94%">All other characters are treated as literal characters. (For
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* example, "[aeiou]" specifies just the letters a, e, i, o, and u.)</td>
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* </tr>
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* </table>
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* </blockquote>
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*
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* <p>For a more complete explanation, see <a
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* href="http://www.ibm.com/java/education/boundaries/boundaries.html">http://www.ibm.com/java/education/boundaries/boundaries.html</a>.
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* For examples, see the resource data (which is annotated).</p>
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*
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* @author Richard Gillam
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*/
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class U_I18N_API RuleBasedBreakIterator : public BreakIterator {
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public:
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/**
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* A token used as a character-category value to identify ignore characters
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*/
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static const int8_t IGNORE;
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private:
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/**
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* The state number of the starting state
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*/
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static const int16_t START_STATE;
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/**
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* The state-transition value indicating "stop"
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*/
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static const int16_t STOP_STATE;
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protected:
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/**
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* The character iterator through which this BreakIterator accesses the text
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*/
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CharacterIterator* text;
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/**
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* The data tables this iterator uses to determine the break positions
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*/
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RuleBasedBreakIteratorTables* tables;
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private:
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/**
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* Class ID
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*/
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static const char fgClassID;
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/*
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* HSYS: To be revisited, once the ctor are made public.
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*/
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protected:
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//=======================================================================
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// constructors
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//=======================================================================
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// This constructor uses the udata interface to create a BreakIterator whose
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// internal tables live in a memory-mapped file. "image" is a pointer to the
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// beginning of that file.
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RuleBasedBreakIterator(UDataMemory* image);
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public:
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/**
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* Copy constructor. Will produce a collator with the same behavior,
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* and which iterates over the same text, as the one passed in.
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*/
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RuleBasedBreakIterator(const RuleBasedBreakIterator& that);
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//=======================================================================
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// boilerplate
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//=======================================================================
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/**
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* Destructor
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*/
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virtual ~RuleBasedBreakIterator();
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/**
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* Assignment operator. Sets this iterator to have the same behavior,
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* and iterate over the same text, as the one passed in.
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*/
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RuleBasedBreakIterator& operator=(const RuleBasedBreakIterator& that);
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/**
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* Equality operator. Returns TRUE if both BreakIterators are of the
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* same class, have the same behavior, and iterate over the same text.
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*/
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virtual UBool operator==(const BreakIterator& that) const;
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/**
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* Not-equal operator. If operator== returns TRUE, this returns FALSE,
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* and vice versa.
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*/
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UBool operator!=(const BreakIterator& that) const;
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/**
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* Returns a newly-constructed RuleBasedBreakIterator with the same
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* behavior, and iterating over the same text, as this one.
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*/
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virtual BreakIterator* clone(void) const;
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/**
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* Compute a hash code for this BreakIterator
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* @return A hash code
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*/
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virtual int32_t hashCode(void) const;
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/**
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* Returns the description used to create this iterator
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*/
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virtual const UnicodeString& getRules(void) const;
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//=======================================================================
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// BreakIterator overrides
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//=======================================================================
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/**
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* Return a CharacterIterator over the text being analyzed. This version
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* of this method returns the actual CharacterIterator we're using internally.
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* Changing the state of this iterator can have undefined consequences. If
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* you need to change it, clone it first.
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* @return An iterator over the text being analyzed.
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*/
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virtual const CharacterIterator& getText(void) const;
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#ifdef ICU_ENABLE_DEPRECATED_BREAKITERATOR
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/**
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* Returns a newly-created CharacterIterator that the caller is to take
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* ownership of.
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* @deprecated This will be removed after 2000-Dec-31.
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* THIS FUNCTION SHOULD NOT BE HERE. IT'S HERE BECAUSE BreakIterator DEFINES
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* IT AS PURE VIRTUAL, FORCING RBBI TO IMPLEMENT IT. IT SHOULD BE REMOVED
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* FROM *BOTH* CLASSES. Use getText() instead.
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*/
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virtual CharacterIterator* createText(void) const;
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/**
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* Set the iterator to analyze a new piece of text. This function resets
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* the current iteration position to the beginning of the text.
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* @param newText The text to analyze.
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* @deprecated
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* THIS FUNCTION SHOULD NOT BE HERE. IT'S HERE BECAUSE BreakIterator DEFINES
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* IT AS PURE VIRTUAL, FORCING RBBI TO IMPLEMENT IT. IT SHOULD BE REMOVED
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* FROM *BOTH* CLASSES. Use the other setText() instead.
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*/
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virtual void setText(const UnicodeString* newText);
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#endif
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/**
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* Set the iterator to analyze a new piece of text. This function resets
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* the current iteration position to the beginning of the text.
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* @param newText An iterator over the text to analyze. The BreakIterator
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* takes ownership of the character iterator. The caller MUST NOT delete it!
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*/
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virtual void adoptText(CharacterIterator* newText);
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/**
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* Set the iterator to analyze a new piece of text. This function resets
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* the current iteration position to the beginning of the text.
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* @param newText The text to analyze.
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*/
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virtual void setText(const UnicodeString& newText);
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/**
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* Sets the current iteration position to the beginning of the text.
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* (i.e., the CharacterIterator's starting offset).
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* @return The offset of the beginning of the text.
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*/
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virtual int32_t first(void);
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/**
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* Sets the current iteration position to the end of the text.
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* (i.e., the CharacterIterator's ending offset).
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* @return The text's past-the-end offset.
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*/
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virtual int32_t last(void);
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/**
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* Advances the iterator either forward or backward the specified number of steps.
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* Negative values move backward, and positive values move forward. This is
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* equivalent to repeatedly calling next() or previous().
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* @param n The number of steps to move. The sign indicates the direction
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* (negative is backwards, and positive is forwards).
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* @return The character offset of the boundary position n boundaries away from
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* the current one.
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*/
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virtual int32_t next(int32_t n);
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/**
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* Advances the iterator to the next boundary position.
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* @return The position of the first boundary after this one.
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*/
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virtual int32_t next(void);
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/**
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* Advances the iterator backwards, to the last boundary preceding this one.
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* @return The position of the last boundary position preceding this one.
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*/
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virtual int32_t previous(void);
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/**
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* Sets the iterator to refer to the first boundary position following
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* the specified position.
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* @offset The position from which to begin searching for a break position.
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* @return The position of the first break after the current position.
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*/
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virtual int32_t following(int32_t offset);
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/**
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* Sets the iterator to refer to the last boundary position before the
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* specified position.
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* @offset The position to begin searching for a break from.
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* @return The position of the last boundary before the starting position.
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*/
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virtual int32_t preceding(int32_t offset);
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/**
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* Returns true if the specfied position is a boundary position. As a side
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* effect, leaves the iterator pointing to the first boundary position at
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* or after "offset".
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* @param offset the offset to check.
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* @return True if "offset" is a boundary position.
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*/
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virtual UBool isBoundary(int32_t offset);
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/**
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* Returns the current iteration position.
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* @return The current iteration position.
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*/
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virtual int32_t current(void) const;
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/**
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* Returns a unique class ID POLYMORPHICALLY. Pure virtual override.
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* This method is to implement a simple version of RTTI, since not all
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* C++ compilers support genuine RTTI. Polymorphic operator==() and
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* clone() methods call this method.
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*
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* @return The class ID for this object. All objects of a
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* given class have the same class ID. Objects of
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* other classes have different class IDs.
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*/
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inline virtual UClassID getDynamicClassID(void) const;
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/**
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* Returns the class ID for this class. This is useful only for
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* comparing to a return value from getDynamicClassID(). For example:
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*
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* Base* polymorphic_pointer = createPolymorphicObject();
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* if (polymorphic_pointer->getDynamicClassID() ==
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* Derived::getStaticClassID()) ...
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*
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* @return The class ID for all objects of this class.
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*/
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inline static UClassID getStaticClassID(void);
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virtual BreakIterator * createBufferClone(void *stackBuffer,
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int32_t &BufferSize,
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UErrorCode &status);
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protected:
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//=======================================================================
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// implementation
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//=======================================================================
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/**
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* This method is the actual implementation of the next() method. All iteration
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* vectors through here. This method initializes the state machine to state 1
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* and advances through the text character by character until we reach the end
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* of the text or the state machine transitions to state 0. We update our return
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* value every time the state machine passes through a possible end state.
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*/
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virtual int32_t handleNext(void);
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/**
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* This method backs the iterator back up to a "safe position" in the text.
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* This is a position that we know, without any context, must be a break position.
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* The various calling methods then iterate forward from this safe position to
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* the appropriate position to return. (For more information, see the description
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* of buildBackwardsStateTable() in RuleBasedBreakIterator.Builder.)
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*/
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virtual int32_t handlePrevious(void);
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/**
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* Dumps caches and performs other actions associated with a complete change
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* in text or iteration position. This function is a no-op in RuleBasedBreakIterator,
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* but subclasses can and do override it.
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*/
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virtual void reset(void);
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private:
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/**
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* Constructs a RuleBasedBreakIterator that uses the already-created
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* tables object that is passed in as a parameter.
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*/
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RuleBasedBreakIterator(RuleBasedBreakIteratorTables* adoptTables);
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friend class BreakIterator;
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};
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inline UBool RuleBasedBreakIterator::operator!=(const BreakIterator& that) const {
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return !operator==(that);
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}
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inline UClassID RuleBasedBreakIterator::getDynamicClassID(void) const {
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return RuleBasedBreakIterator::getStaticClassID();
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}
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inline UClassID RuleBasedBreakIterator::getStaticClassID(void) {
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return (UClassID)(&fgClassID);
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}
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U_NAMESPACE_END
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#endif
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