codekingpro/portable-devtools

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 
27U_NAMESPACE_BEGIN
28
29class ParsePosition;
30class UnicodeFunctor;
31class UnicodeSet;
32class 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 * "$start=alpha"), then the call lookup("start") will return the
43 * char[] array ['a', 'l', 'p', 'h', 'a'].
44 *
45 * <p>The second kind of mapping is between character values and
46 * UnicodeMatcher objects.  This is used by RuleBasedTransliterator,
47 * which uses characters in the private use area to represent objects
48 * such as UnicodeSets.  If U+E015 is mapped to the UnicodeSet [a-z],
49 * then lookupMatcher(0xE015) will return the UnicodeSet [a-z].
50 *
51 * <p>Finally, a symbol table defines parsing behavior for symbolic
52 * names.  All symbolic names start with the SYMBOL_REF character.
53 * When a parser encounters this character, it calls parseReference()
54 * with the position immediately following the SYMBOL_REF.  The symbol
55 * table parses the name, if there is one, and returns it.
56 *
57 * @stable ICU 2.8
58 */
59class U_COMMON_API SymbolTable /* not : public UObject because this is an interface/mixin class */ {
60public:
61
62    /**
63     * The character preceding a symbol reference name.
64     * @stable ICU 2.8
65     */
66    enum { SYMBOL_REF = 0x0024 /*$*/ };
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>NULL</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>NULL</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>NULL</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 NULL 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};
115U_NAMESPACE_END
116
117#endif /* U_SHOW_CPLUSPLUS_API */
118
119#endif
120