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Created: 2026-01-25 06:58

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/src/icu/icu4c/source/common/unicode/symtable.h
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// © 2016 and later: Unicode, Inc. and others.
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// License & terms of use: http://www.unicode.org/copyright.html
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/*
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**********************************************************************
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*   Copyright (c) 2000-2005, International Business Machines
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*   Corporation and others.  All Rights Reserved.
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**********************************************************************
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*   Date        Name        Description
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*   02/04/00    aliu        Creation.
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**********************************************************************
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*/
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#ifndef SYMTABLE_H
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#define SYMTABLE_H
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#include "unicode/utypes.h"
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#if U_SHOW_CPLUSPLUS_API
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#include "unicode/uobject.h"
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/**
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 * \file
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 * \brief C++ API: An interface that defines both lookup protocol and parsing of
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 * symbolic names.
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 */
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U_NAMESPACE_BEGIN
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class ParsePosition;
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class UnicodeFunctor;
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class UnicodeSet;
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class UnicodeString;
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/**
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 * An interface that defines both lookup protocol and parsing of
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 * symbolic names.
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 *
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 * <p>A symbol table maintains two kinds of mappings.  The first is
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 * between symbolic names and their values.  For example, if the
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 * variable with the name "start" is set to the value "alpha"
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 * (perhaps, though not necessarily, through an expression such as
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 * "$start=alpha"), then the call lookup("start") will return the
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 * char[] array ['a', 'l', 'p', 'h', 'a'].
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 *
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 * <p>The second kind of mapping is between character values and
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 * UnicodeMatcher objects.  This is used by RuleBasedTransliterator,
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 * which uses characters in the private use area to represent objects
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 * such as UnicodeSets.  If U+E015 is mapped to the UnicodeSet [a-z],
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 * then lookupMatcher(0xE015) will return the UnicodeSet [a-z].
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 *
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 * <p>Finally, a symbol table defines parsing behavior for symbolic
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 * names.  All symbolic names start with the SYMBOL_REF character.
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 * When a parser encounters this character, it calls parseReference()
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 * with the position immediately following the SYMBOL_REF.  The symbol
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 * table parses the name, if there is one, and returns it.
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 *
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 * @stable ICU 2.8
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 */
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class U_COMMON_API SymbolTable /* not : public UObject because this is an interface/mixin class */ {
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public:
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    /**
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     * The character preceding a symbol reference name.
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     * @stable ICU 2.8
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     */
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    enum { SYMBOL_REF = 0x0024 /*$*/ };
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    /**
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     * Destructor.
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     * @stable ICU 2.8
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     */
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    virtual ~SymbolTable();
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    /**
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     * Lookup the characters associated with this string and return it.
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     * Return <tt>nullptr</tt> if no such name exists.  The resultant
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     * string may have length zero.
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     * @param s the symbolic name to lookup
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     * @return a string containing the name's value, or <tt>nullptr</tt> if
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     * there is no mapping for s.
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     * @stable ICU 2.8
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     */
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    virtual const UnicodeString* lookup(const UnicodeString& s) const = 0;
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    /**
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     * Returns a pointer to a pre-parsed set associated with the variable with
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     * the given name, or null if there is no such set (as is the case for an
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     * undefined or string-valued variable).
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     * @internal
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     */
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    virtual const UnicodeSet* lookupSet(const UnicodeString& /*name*/) const {
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        return nullptr;
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    }
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    /**
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     * Lookup the UnicodeMatcher associated with the given character, and
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     * return it.  Return <tt>nullptr</tt> if not found.
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     * @param ch a 32-bit code point from 0 to 0x10FFFF inclusive.
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     * @return the UnicodeMatcher object represented by the given
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     * character, or nullptr if there is no mapping for ch.
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     * @stable ICU 2.8
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     */
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    virtual const UnicodeFunctor* lookupMatcher(UChar32 ch) const = 0;
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    /**
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     * Parse a symbol reference name from the given string, starting
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     * at the given position.  If no valid symbol reference name is
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     * found, return the empty string and leave pos unchanged.  That is, if the
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     * character at pos cannot start a name, or if pos is at or after
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     * text.length(), then return an empty string.  This indicates an
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     * isolated SYMBOL_REF character.
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     * @param text the text to parse for the name
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     * @param pos on entry, the index of the first character to parse.
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     * This is the character following the SYMBOL_REF character.  On
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     * exit, the index after the last parsed character.  If the parse
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     * failed, pos is unchanged on exit.
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     * @param limit the index after the last character to be parsed.
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     * @return the parsed name, or an empty string if there is no
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     * valid symbolic name at the given position.
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     * @stable ICU 2.8
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     */
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    virtual UnicodeString parseReference(const UnicodeString& text,
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                                         ParsePosition& pos, int32_t limit) const = 0;
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};
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U_NAMESPACE_END
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#endif /* U_SHOW_CPLUSPLUS_API */
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#endif