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/*
 *******************************************************************************
 * 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); }





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