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