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