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// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html#License
/*
*******************************************************************************
* Copyright (C) 1996-2005, International Business Machines Corporation and *
* others. All Rights Reserved. *
*******************************************************************************
*/
package com.ibm.icu.text;
import java.text.ParsePosition;
/**
* An interface that defines both lookup protocol and parsing of
* symbolic names.
*
* This interface is used by UnicodeSet to resolve $Variable style
* references that appear in set patterns. RBBI and Transliteration
* both independently implement this interface.
*
*
A symbol table maintains two kinds of mappings. The first is
* between symbolic names and their values. For example, if the
* variable with the name "start" is set to the value "alpha"
* (perhaps, though not necessarily, through an expression such as
* "$start=alpha"), then the call lookup("start") will return the
* char[] array ['a', 'l', 'p', 'h', 'a'].
*
*
The second kind of mapping is between character values and
* UnicodeMatcher objects. This is used by RuleBasedTransliterator,
* which uses characters in the private use area to represent objects
* such as UnicodeSets. If U+E015 is mapped to the UnicodeSet [a-z],
* then lookupMatcher(0xE015) will return the UnicodeSet [a-z].
*
*
Finally, a symbol table defines parsing behavior for symbolic
* names. All symbolic names start with the SYMBOL_REF character.
* When a parser encounters this character, it calls parseReference()
* with the position immediately following the SYMBOL_REF. The symbol
* table parses the name, if there is one, and returns it.
*
* @stable ICU 2.8
*/
public interface SymbolTable {
/**
* The character preceding a symbol reference name.
* @stable ICU 2.8
*/
static final char SYMBOL_REF = '$';
/**
* Lookup the characters associated with this string and return it.
* Return null if no such name exists. The resultant
* array may have length zero.
* @param s the symbolic name to lookup
* @return a char array containing the name's value, or null if
* there is no mapping for s.
* @stable ICU 2.8
*/
char[] lookup(String s);
/**
* Lookup the UnicodeMatcher associated with the given character, and
* return it. Return null if not found.
* @param ch a 32-bit code point from 0 to 0x10FFFF inclusive.
* @return the UnicodeMatcher object represented by the given
* character, or null if there is no mapping for ch.
* @stable ICU 2.8
*/
UnicodeMatcher lookupMatcher(int ch);
/**
* Parse a symbol reference name from the given string, starting
* at the given position. If no valid symbol reference name is
* found, return null and leave pos unchanged. That is, if the
* character at pos cannot start a name, or if pos is at or after
* text.length(), then return null. This indicates an isolated
* SYMBOL_REF character.
* @param text the text to parse for the name
* @param pos on entry, the index of the first character to parse.
* This is the character following the SYMBOL_REF character. On
* exit, the index after the last parsed character. If the parse
* failed, pos is unchanged on exit.
* @param limit the index after the last character to be parsed.
* @return the parsed name, or null if there is no valid symbolic
* name at the given position.
* @stable ICU 2.8
*/
String parseReference(String text, ParsePosition pos, int limit);
}