icuSources/common/unicode/symtable.h

   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
  22 U_NAMESPACE_BEGIN
  23
  24 class ParsePosition;
  25 class UnicodeFunctor;
  26 class UnicodeSet;
  27 class 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  * "$start=alpha"), then the call lookup("start") will return the
  38  * char[] array ['a', 'l', 'p', 'h', 'a'].
  39  *
  40  * <p>The second kind of mapping is between character values and
  41  * UnicodeMatcher objects.  This is used by RuleBasedTransliterator,
  42  * which uses characters in the private use area to represent objects
  43  * such as UnicodeSets.  If U+E015 is mapped to the UnicodeSet [a-z],
  44  * then lookupMatcher(0xE015) will return the UnicodeSet [a-z].
  45  *
  46  * <p>Finally, a symbol table defines parsing behavior for symbolic
  47  * names.  All symbolic names start with the SYMBOL_REF character.
  48  * When a parser encounters this character, it calls parseReference()
  49  * with the position immediately following the SYMBOL_REF.  The symbol
  50  * table parses the name, if there is one, and returns it.
  51  *
  52  * @stable ICU 2.8
  53  */
  54 class U_COMMON_API SymbolTable /* not : public UObject because this is an interface/mixin class */ {
  55 public:
  56
  57     /**
  58      * The character preceding a symbol reference name.
  59      * @stable ICU 2.8
  60      */
  61     enum { SYMBOL_REF = 0x0024 /*$*/ };
  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 };
 110 U_NAMESPACE_END
 111
 112 #endif