470 lines
20 KiB
C++
470 lines
20 KiB
C++
/*
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**********************************************************************
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* Copyright (C) 2001 IBM and others. All rights reserved.
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**********************************************************************
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* Date Name Description
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* 03/22/2000 helena Creation.
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**********************************************************************
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*/
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#ifndef STSEARCH_H
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#define STSEARCH_H
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#include "unicode/tblcoll.h"
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#include "unicode/coleitr.h"
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#include "unicode/search.h"
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U_NAMESPACE_BEGIN
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/**
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* <tt>StringSearch</tt> is a <tt>SearchIterator</tt> that provides
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* language-sensitive text searching based on the comparison rules defined
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* in a {@link RuleBasedCollator} object.
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* StringSearch ensures that language eccentricity can be
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* handled, e.g. for the German collator, characters ß and SS will be matched
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* if case is chosen to be ignored.
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* See the <a href=http://oss.software.ibm.com/icu/develop/collation/ICU_collation_design.htm>
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* "ICU Collation Design Document"</a> for more information.
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* <p>
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* The algorithm implemented is a modified form of the Boyer Moore's search.
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* For more information see
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* <a href=http://oss.software.ibm.com/icu/docs/papers/text-search.html>
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* "Efficient Text Searching in Java"</a>, published in <i>Java Report</i>
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* in February, 1999, for further information on the algorithm.
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* <p>
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* There are 2 match options for selection:<br>
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* Let S' be the sub-string of a text string S between the offsets start and
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* end <start, end>.
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* <br>
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* A pattern string P matches a text string S at the offsets <start, end>
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* if
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* <pre>
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* option 1. Some canonical equivalent of P matches some canonical equivalent
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* of S'
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* option 2. P matches S' and if P starts or ends with a combining mark,
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* there exists no non-ignorable combining mark before or after S?
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* in S respectively.
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* </pre>
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* Option 2. will be the default·
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* <p>
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* This search has APIs similar to that of other text iteration mechanisms
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* such as the break iterators in <tt>BreakIterator</tt>. Using these
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* APIs, it is easy to scan through text looking for all occurances of
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* a given pattern. This search iterator allows changing of direction by
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* calling a <tt>reset</tt> followed by a <tt>next</tt> or <tt>previous</tt>.
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* Though a direction change can occur without calling <tt>reset</tt> first,
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* this operation comes with some speed penalty.
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* Match results in the forward direction will match the result matches in
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* the backwards direction in the reverse order
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* <p>
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* <tt>SearchIterator</tt> provides APIs to specify the starting position
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* within the text string to be searched, e.g. <tt>setOffset</tt>,
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* <tt>preceding</tt> and <tt>following</tt>. Since the
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* starting position will be set as it is specified, please take note that
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* there are some danger points which the search may render incorrect
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* results:
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* <ul>
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* <li> The midst of a substring that requires normalization.
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* <li> If the following match is to be found, the position should not be the
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* second character which requires to be swapped with the preceding
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* character. Vice versa, if the preceding match is to be found,
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* position to search from should not be the first character which
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* requires to be swapped with the next character. E.g certain Thai and
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* Lao characters require swapping.
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* <li> If a following pattern match is to be found, any position within a
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* contracting sequence except the first will fail. Vice versa if a
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* preceding pattern match is to be found, a invalid starting point
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* would be any character within a contracting sequence except the last.
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* <\ul>
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* <p>
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* A breakiterator can be used if only matches at logical breaks are desired.
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* Using a breakiterator will only give you results that exactly matches the
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* boundaries given by the breakiterator. For instance the pattern "e" will
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* not be found in the string "\u00e9" if a character break iterator is used.
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* <p>
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* Options are provided to handle overlapping matches.
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* E.g. In English, overlapping matches produces the result 0 and 2
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* for the pattern "abab" in the text "ababab", where else mutually
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* exclusive matches only produce the result of 0.
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* <p>
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* Though collator attributes will be taken into consideration while
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* performing matches, there are no APIs here for setting and getting the
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* attributes. These attributes can be set by getting the collator
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* from <tt>getCollator</tt> and using the APIs in <tt>coll.h</tt>.
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* Lastly to update StringSearch to the new collator attributes,
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* reset() has to be called.
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* <p>
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* Restriction: <br>
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* Currently there are no composite characters that consists of a
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* character with combining class > 0 before a character with combining
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* class == 0. However, if such a character exists in the future,
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* StringSearch does not guarantee the results for option 1.
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* <p>
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* Consult the <tt>SearchIterator</tt> documentation for information on
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* and examples of how to use instances of this class to implement text
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* searching.
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* <pre><code>
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* UnicodeString target("The quick brown fox jumped over the lazy fox");
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* UnicodeString pattern("fox");
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*
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* SearchIterator *iter = new StringSearch(pattern, target);
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*
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* for (int pos = iter->first(); pos != USEARCH_DONE;
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* pos = iter->next()) {
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* printf("Found match at %d pos, length is %d\n", pos,
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* iter.getMatchLength());
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* }
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* </code></pre>
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* @see SearchIterator
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* @see RuleBasedCollator
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* @since ICU 2.0
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*/
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class U_I18N_API StringSearch : public SearchIterator
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{
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public:
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// public constructors and destructors --------------------------------
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/**
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* Creating a <tt>StringSearch</tt> instance using the argument locale
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* language rule set. A collator will be created in the process, which
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* will be owned by this instance and will be deleted in during
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* destruction
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* @param pattern The text for which this object will search.
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* @param text The text in which to search for the pattern.
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* @param locale A locale which defines the language-sensitive
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* comparison rules used to determine whether text in the
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* pattern and target matches.
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* @param breakiter A <tt>BreakIterator</tt> object used to constrain
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* the matches that are found. Matches whose start and end
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* indices in the target text are not boundaries as
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* determined by the <tt>BreakIterator</tt> are
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* ignored. If this behavior is not desired,
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* <tt>NULL</tt> can be passed in instead.
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* @param status for errors if any. If pattern or text is NULL, or if
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* either the length of pattern or text is 0 then an
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* U_ILLEGAL_ARGUMENT_ERROR is returned.
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* @draft ICU 2.0
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*/
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StringSearch(const UnicodeString &pattern, const UnicodeString &text,
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const Locale &locale,
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BreakIterator *breakiter,
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UErrorCode &status);
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/**
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* Creating a <tt>StringSearch</tt> instance using the argument collator
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* language rule set. Note, user retains the ownership of this collator,
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* it does not get destroyed during this instance's destruction.
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* @param pattern The text for which this object will search.
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* @param text The text in which to search for the pattern.
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* @param coll A <tt>RuleBasedCollator</tt> object which defines
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* the language-sensitive comparison rules used to
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* determine whether text in the pattern and target
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* matches. User is responsible for the clearing of this
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* object.
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* @param breakiter A <tt>BreakIterator</tt> object used to constrain
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* the matches that are found. Matches whose start and end
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* indices in the target text are not boundaries as
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* determined by the <tt>BreakIterator</tt> are
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* ignored. If this behavior is not desired,
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* <tt>NULL</tt> can be passed in instead.
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* @param status for errors if any. If either the length of pattern or
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* text is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned.
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* @draft ICU 2.0
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*/
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StringSearch(const UnicodeString &pattern,
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const UnicodeString &text,
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RuleBasedCollator *coll,
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BreakIterator *breakiter,
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UErrorCode &status);
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/**
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* Creating a <tt>StringSearch</tt> instance using the argument locale
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* language rule set. A collator will be created in the process, which
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* will be owned by this instance and will be deleted in during
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* destruction
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* <p>
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* Note: No parsing of the text within the <tt>CharacterIterator</tt>
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* will be done during searching for this version. The block of text
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* in <tt>CharacterIterator</tt> will be used as it is.
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* @param pattern The text for which this object will search.
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* @param text The text iterator in which to search for the pattern.
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* @param locale A locale which defines the language-sensitive
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* comparison rules used to determine whether text in the
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* pattern and target matches. User is responsible for
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* the clearing of this object.
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* @param breakiter A <tt>BreakIterator</tt> object used to constrain
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* the matches that are found. Matches whose start and end
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* indices in the target text are not boundaries as
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* determined by the <tt>BreakIterator</tt> are
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* ignored. If this behavior is not desired,
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* <tt>NULL</tt> can be passed in instead.
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* @param status for errors if any. If either the length of pattern or
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* text is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned.
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* @draft ICU 2.0
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*/
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StringSearch(const UnicodeString &pattern, CharacterIterator &text,
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const Locale &locale,
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BreakIterator *breakiter,
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UErrorCode &status);
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/**
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* Creating a <tt>StringSearch</tt> instance using the argument collator
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* language rule set. Note, user retains the ownership of this collator,
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* it does not get destroyed during this instance's destruction.
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* <p>
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* Note: No parsing of the text within the <tt>CharacterIterator</tt>
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* will be done during searching for this version. The block of text
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* in <tt>CharacterIterator</tt> will be used as it is.
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* @param pattern The text for which this object will search.
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* @param text The text in which to search for the pattern.
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* @param coll A <tt>RuleBasedCollator</tt> object which defines
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* the language-sensitive comparison rules used to
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* determine whether text in the pattern and target
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* matches. User is responsible for the clearing of this
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* object.
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* @param breakiter A <tt>BreakIterator</tt> object used to constrain
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* the matches that are found. Matches whose start and end
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* indices in the target text are not boundaries as
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* determined by the <tt>BreakIterator</tt> are
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* ignored. If this behavior is not desired,
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* <tt>NULL</tt> can be passed in instead.
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* @param status for errors if any. If either the length of pattern or
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* text is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned.
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* @draft ICU 2.0
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*/
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StringSearch(const UnicodeString &pattern, CharacterIterator &text,
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RuleBasedCollator *coll,
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BreakIterator *breakiter,
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UErrorCode &status);
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/**
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* Copy constructor that creates a StringSearch instance with the same
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* behavior, and iterating over the same text.
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* @param that StringSearch instance to be copied.
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* @draft ICU 2.0
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*/
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StringSearch(const StringSearch &that);
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/**
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* Destructor. Cleans up the search iterator data struct.
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* If a collator is created in the constructor, it will be destroyed here.
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* @draft ICU 2.0
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*/
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virtual ~StringSearch(void);
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// operator overloading ---------------------------------------------
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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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* @param that instance to be copied.
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* @draft ICU 2.0
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*/
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StringSearch & operator=(const StringSearch &that);
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/**
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* Equality operator.
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* @param that instance to be compared.
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* @return TRUE if both instances have the same attributes,
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* breakiterators, collators and iterate over the same text
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* while looking for the same pattern.
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* @draft ICU 2.0
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*/
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virtual UBool operator==(const SearchIterator &that) const;
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// public get and set methods ----------------------------------------
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/**
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* Sets the index to point to the given position, and clears any state
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* that's affected.
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* <p>
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* This method takes the argument index and sets the position in the text
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* string accordingly without checking if the index is pointing to a
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* valid starting point to begin searching.
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* @param position within the text to be set
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* @param status for errors if it occurs
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* @draft ICU 2.0
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*/
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virtual void setOffset(int32_t position, UErrorCode &status);
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/**
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* Return the current index in the text being searched.
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* If the iteration has gone past the end of the text
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* (or past the beginning for a backwards search), {@link #USEARCH_DONE}
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* is returned.
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* @return current index in the text being searched.
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* @draft ICU 2.0
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*/
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virtual int32_t getOffset(void) const;
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/**
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* Set the target text to be searched.
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* Text iteration will hence begin at the start of the text string.
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* This method is
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* useful if you want to re-use an iterator to search for the same
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* pattern within a different body of text.
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* @param text text string to be searched
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* @param status for errors if any. If the text length is 0 then an
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* U_ILLEGAL_ARGUMENT_ERROR is returned.
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* @draft ICU 2.0
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*/
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virtual void setText(const UnicodeString &text, UErrorCode &status);
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/**
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* Set the target text to be searched.
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* Text iteration will hence begin at the start of the text string.
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* This method is
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* useful if you want to re-use an iterator to search for the same
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* pattern within a different body of text.
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* Note: No parsing of the text within the <tt>CharacterIterator</tt>
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* will be done during searching for this version. The block of text
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* in <tt>CharacterIterator</tt> will be used as it is.
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* @param text text string to be searched
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* @param status for errors if any. If the text length is 0 then an
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* U_ILLEGAL_ARGUMENT_ERROR is returned.
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* @draft ICU 2.0
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*/
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virtual void setText(CharacterIterator &text, UErrorCode &status);
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/**
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* Gets the collator used for the language rules.
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* <p>
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* Deleting the returned <tt>RuleBasedCollator</tt> before calling
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* the destructor would cause the string search to fail.
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* The destructor will delete the collator if this instance owns it
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* @return collator used for string search
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* @draft ICU 2.0
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*/
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RuleBasedCollator * getCollator() const;
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/**
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* Sets the collator used for the language rules. User retains the
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* ownership of this collator, thus the responsibility of deletion lies
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* with the user. This method causes internal data such as Boyer-Moore
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* shift tables to be recalculated, but the iterator's position is
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* unchanged.
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* @param coll collator
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* @param status for errors if any
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* @draft ICU 2.0
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*/
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void setCollator(RuleBasedCollator *coll, UErrorCode &status);
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/**
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* Sets the pattern used for matching.
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* Internal data like the Boyer Moore table will be recalculated, but
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* the iterator's position is unchanged.
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* @param pattern search pattern to be found
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* @param status for errors if any. If the pattern length is 0 then an
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* U_ILLEGAL_ARGUMENT_ERROR is returned.
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* @draft ICU 2.0
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*/
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void setPattern(const UnicodeString &pattern, UErrorCode &status);
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/**
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* Gets the search pattern.
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* @return pattern used for matching
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* @draft ICU 2.0
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*/
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const UnicodeString & getPattern() const;
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// public methods ----------------------------------------------------
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/**
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* Reset the iteration.
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* Search will begin at the start of the text string if a forward
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* iteration is initiated before a backwards iteration. Otherwise if
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* a backwards iteration is initiated before a forwards iteration, the
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* search will begin at the end of the text string.
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* @draft ICU 2.0
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*/
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virtual void reset();
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/**
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* Returns a copy of StringSearch with the same behavior, and
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* iterating over the same text, as this one. Note that all data will be
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* replicated, except for the user-specified collator and the
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* breakiterator.
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* @return cloned object
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* @draft ICU 2.0
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*/
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virtual SearchIterator * safeClone(void) const;
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protected:
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// protected method -------------------------------------------------
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/**
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* Search forward for matching text, starting at a given location.
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* Clients should not call this method directly; instead they should
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* call {@link SearchIterator#next}.
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* <p>
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* If a match is found, this method returns the index at which the match
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* starts and calls {@link SearchIterator#setMatchLength} with the number
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* of characters in the target text that make up the match. If no match
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* is found, the method returns <tt>USEARCH_DONE</tt>.
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* <p>
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* The <tt>StringSearch</tt> is adjusted so that its current index
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* (as returned by {@link #getOffset}) is the match position if one was
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* found.
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* If a match is not found, <tt>USEARCH_DONE</tt> will be returned and
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* the <tt>StringSearch</tt> will be adjusted to the index USEARCH_DONE.
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* @param position The index in the target text at which the search
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* starts
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* @param status for errors if any occurs
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* @return The index at which the matched text in the target starts, or
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* USEARCH_DONE if no match was found.
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*/
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virtual int32_t handleNext(int32_t position, UErrorCode &status);
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/**
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* Search backward for matching text, starting at a given location.
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* Clients should not call this method directly; instead they should call
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* <tt>SearchIterator.previous()</tt>, which this method overrides.
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* <p>
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* If a match is found, this method returns the index at which the match
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* starts and calls {@link SearchIterator#setMatchLength} with the number
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* of characters in the target text that make up the match. If no match
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* is found, the method returns <tt>USEARCH_DONE</tt>.
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* <p>
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* The <tt>StringSearch</tt> is adjusted so that its current index
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* (as returned by {@link #getOffset}) is the match position if one was
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* found.
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* If a match is not found, <tt>USEARCH_DONE</tt> will be returned and
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* the <tt>StringSearch</tt> will be adjusted to the index USEARCH_DONE.
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* @param position The index in the target text at which the search
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* starts.
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* @param status for errors if any occurs
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* @return The index at which the matched text in the target starts, or
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* USEARCH_DONE if no match was found.
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*/
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virtual int32_t handlePrev(int32_t position, UErrorCode &status);
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private :
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// private data members ----------------------------------------------
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/**
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* RuleBasedCollator, contains exactly the same UCollator * in m_strsrch_
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*/
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RuleBasedCollator m_collator_;
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/**
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* Pattern text
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*/
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UnicodeString m_pattern_;
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/**
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* Corresponding collation rules
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*/
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UnicodeString m_collation_rules_;
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/**
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* String search struct data
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*/
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UStringSearch *m_strsrch_;
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};
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U_NAMESPACE_END
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#endif
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