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symtable.h (4386B)

      1 // © 2016 and later: Unicode, Inc. and others.
      2 // License & terms of use: http://www.unicode.org/copyright.html
      3 /*
      4 **********************************************************************
      5 *   Copyright (c) 2000-2005, International Business Machines
      6 *   Corporation and others.  All Rights Reserved.
      7 **********************************************************************
      8 *   Date        Name        Description
      9 *   02/04/00    aliu        Creation.
     10 **********************************************************************
     11 */
     12 #ifndef SYMTABLE_H
     13 #define SYMTABLE_H
     14 
     15 #include "unicode/utypes.h"
     16 
     17 #if U_SHOW_CPLUSPLUS_API
     18 
     19 #include "unicode/uobject.h"
     20 
     21 /**
     22 * \file 
     23 * \brief C++ API: An interface that defines both lookup protocol and parsing of
     24 * symbolic names.
     25 */
     26 
     27 U_NAMESPACE_BEGIN
     28 
     29 class ParsePosition;
     30 class UnicodeFunctor;
     31 class UnicodeSet;
     32 class UnicodeString;
     33 
     34 /**
     35 * An interface that defines both lookup protocol and parsing of
     36 * symbolic names.
     37 *
     38 * <p>A symbol table maintains two kinds of mappings.  The first is
     39 * between symbolic names and their values.  For example, if the
     40 * variable with the name "start" is set to the value "alpha"
     41 * (perhaps, though not necessarily, through an expression such as
     42 * "$start=alpha"), then the call lookup("start") will return the
     43 * char[] array ['a', 'l', 'p', 'h', 'a'].
     44 *
     45 * <p>The second kind of mapping is between character values and
     46 * UnicodeMatcher objects.  This is used by RuleBasedTransliterator,
     47 * which uses characters in the private use area to represent objects
     48 * such as UnicodeSets.  If U+E015 is mapped to the UnicodeSet [a-z],
     49 * then lookupMatcher(0xE015) will return the UnicodeSet [a-z].
     50 *
     51 * <p>Finally, a symbol table defines parsing behavior for symbolic
     52 * names.  All symbolic names start with the SYMBOL_REF character.
     53 * When a parser encounters this character, it calls parseReference()
     54 * with the position immediately following the SYMBOL_REF.  The symbol
     55 * table parses the name, if there is one, and returns it.
     56 *
     57 * @stable ICU 2.8
     58 */
     59 class U_COMMON_API SymbolTable /* not : public UObject because this is an interface/mixin class */ {
     60 public:
     61 
     62    /**
     63     * The character preceding a symbol reference name.
     64     * @stable ICU 2.8
     65     */
     66    enum { SYMBOL_REF = 0x0024 /*$*/ };
     67 
     68    /**
     69     * Destructor.
     70     * @stable ICU 2.8
     71     */
     72    virtual ~SymbolTable();
     73 
     74    /**
     75     * Lookup the characters associated with this string and return it.
     76     * Return <tt>nullptr</tt> if no such name exists.  The resultant
     77     * string may have length zero.
     78     * @param s the symbolic name to lookup
     79     * @return a string containing the name's value, or <tt>nullptr</tt> if
     80     * there is no mapping for s.
     81     * @stable ICU 2.8
     82     */
     83    virtual const UnicodeString* lookup(const UnicodeString& s) const = 0;
     84 
     85    /**
     86     * Lookup the UnicodeMatcher associated with the given character, and
     87     * return it.  Return <tt>nullptr</tt> if not found.
     88     * @param ch a 32-bit code point from 0 to 0x10FFFF inclusive.
     89     * @return the UnicodeMatcher object represented by the given
     90     * character, or nullptr if there is no mapping for ch.
     91     * @stable ICU 2.8
     92     */
     93    virtual const UnicodeFunctor* lookupMatcher(UChar32 ch) const = 0;
     94 
     95    /**
     96     * Parse a symbol reference name from the given string, starting
     97     * at the given position.  If no valid symbol reference name is
     98     * found, return the empty string and leave pos unchanged.  That is, if the
     99     * character at pos cannot start a name, or if pos is at or after
    100     * text.length(), then return an empty string.  This indicates an
    101     * isolated SYMBOL_REF character.
    102     * @param text the text to parse for the name
    103     * @param pos on entry, the index of the first character to parse.
    104     * This is the character following the SYMBOL_REF character.  On
    105     * exit, the index after the last parsed character.  If the parse
    106     * failed, pos is unchanged on exit.
    107     * @param limit the index after the last character to be parsed.
    108     * @return the parsed name, or an empty string if there is no
    109     * valid symbolic name at the given position.
    110     * @stable ICU 2.8
    111     */
    112    virtual UnicodeString parseReference(const UnicodeString& text,
    113                                         ParsePosition& pos, int32_t limit) const = 0;
    114 };
    115 U_NAMESPACE_END
    116 
    117 #endif /* U_SHOW_CPLUSPLUS_API */
    118 
    119 #endif