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