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Xerces2 is the next generation of high performance, fully compliant XML parsers in the Apache Xerces family. This new version of Xerces introduces the Xerces Native Interface (XNI), a complete framework for building parser components and configurations that is extremely modular and easy to program. The Apache Xerces2 parser is the reference implementation of XNI but other parser components, configurations, and parsers can be written using the Xerces Native Interface. For complete design and implementation documents, refer to the XNI Manual. Xerces2 is a fully conforming XML Schema 1.0 processor. A partial experimental implementation of the XML Schema 1.1 Structures and Datatypes Working Drafts (December 2009) and an experimental implementation of the XML Schema Definition Language (XSD): Component Designators (SCD) Candidate Recommendation (January 2010) are provided for evaluation. For more information, refer to the XML Schema page. Xerces2 also provides a complete implementation of the Document Object Model Level 3 Core and Load/Save W3C Recommendations and provides a complete implementation of the XML Inclusions (XInclude) W3C Recommendation. It also provides support for OASIS XML Catalogs v1.1. Xerces2 is able to parse documents written according to the XML 1.1 Recommendation, except that it does not yet provide an option to enable normalization checking as described in section 2.13 of this specification. It also handles namespaces according to the XML Namespaces 1.1 Recommendation, and will correctly serialize XML 1.1 documents if the DOM level 3 load/save APIs are in use.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.xerces.util;


/**
 * Shadowed symbol table.
 *
 * The table has a reference to the main symbol table and is 
 * not allowed to add new symbols to the main symbol table. 
 * New symbols are added to the shadow symbol table and are local 
 * to the component using this table.
 * 
 * @author Andy Clark IBM
 * @version $Id: ShadowedSymbolTable.java 447241 2006-09-18 05:12:57Z mrglavas $
 */

public final class ShadowedSymbolTable
extends SymbolTable {

    //
    // Data
    //

    /** Main symbol table. */
    protected SymbolTable fSymbolTable;

    //
    // Constructors
    //

    /** Constructs a shadow of the specified symbol table. */
    public ShadowedSymbolTable(SymbolTable symbolTable) {
        fSymbolTable = symbolTable;
    } // (SymbolTable)

    //
    // SymbolTable methods
    //

    /**
     * Adds the specified symbol to the symbol table and returns a
     * reference to the unique symbol. If the symbol already exists, 
     * the previous symbol reference is returned instead, in order
     * guarantee that symbol references remain unique.
     * 
     * @param symbol The new symbol.
     */
    public String addSymbol(String symbol) {

        if (fSymbolTable.containsSymbol(symbol)) {
            return fSymbolTable.addSymbol(symbol);
        }
        return super.addSymbol(symbol);

    } // addSymbol(String)

    /**
     * Adds the specified symbol to the symbol table and returns a
     * reference to the unique symbol. If the symbol already exists, 
     * the previous symbol reference is returned instead, in order
     * guarantee that symbol references remain unique.
     * 
     * @param buffer The buffer containing the new symbol.
     * @param offset The offset into the buffer of the new symbol.
     * @param length The length of the new symbol in the buffer.
     */
    public String addSymbol(char[] buffer, int offset, int length) {

        if (fSymbolTable.containsSymbol(buffer, offset, length)) {
            return fSymbolTable.addSymbol(buffer, offset, length);
        }
        return super.addSymbol(buffer, offset, length);

    } // addSymbol(char[],int,int):String

    /**
     * Returns a hashcode value for the specified symbol. The value
     * returned by this method must be identical to the value returned
     * by the hash(char[],int,int) method when called
     * with the character array that comprises the symbol string.
     * 
     * @param symbol The symbol to hash.
     */
    public int hash(String symbol) {
        return fSymbolTable.hash(symbol);
    } // hash(String):int

    /**
     * Returns a hashcode value for the specified symbol information. 
     * The value returned by this method must be identical to the value
     * returned by the hash(String) method when called
     * with the string object created from the symbol information.
     * 
     * @param buffer The character buffer containing the symbol.
     * @param offset The offset into the character buffer of the start
     *               of the symbol.
     * @param length The length of the symbol.
     */
    public int hash(char[] buffer, int offset, int length) {
        return fSymbolTable.hash(buffer, offset, length);
    } // hash(char[],int,int):int

} // class ShadowedSymbolTable