/*
 * 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 $Id$
 */

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;
    } // <init>(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 <code>hash(char[],int,int)</code> 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 <code>hash(String)</code> 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
