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A Java implementation of the Amazon Ion data notation.

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/*
 * Copyright 2007-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * or in the "license" file accompanying this file. This file 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 com.amazon.ion.impl;

import static com.amazon.ion.impl._Private_Utils.symtabExtends;

import com.amazon.ion.SymbolTable;

/**
 * Cache to reduce unnecessary calls to
 * {@link _Private_Utils#symtabExtends(SymbolTable, SymbolTable)}. This is
 * only used if the writer is stream copy optimized.
 */
public final class _Private_SymtabExtendsCache
{
    private SymbolTable myWriterSymtab;
    private SymbolTable myReaderSymtab;
    private int myWriterSymtabMaxId;
    private int myReaderSymtabMaxId;
    private boolean myResult;

    public boolean symtabsCompat(SymbolTable writerSymtab,
                                 SymbolTable readerSymtab)
    {
        // If the refs. of both writer's and reader's symtab match and are
        // not modified, skip expensive symtab extends check and return
        // cached result.

        assert writerSymtab != null && readerSymtab != null:
            "writer's and reader's current symtab cannot be null";

        if (myWriterSymtab          == writerSymtab &&
            myReaderSymtab          == readerSymtab &&
            myWriterSymtabMaxId     == writerSymtab.getMaxId() &&
            myReaderSymtabMaxId     == readerSymtab.getMaxId())
        {
            // Not modified, return cached result
            return myResult;
        }

        myResult = symtabExtends(writerSymtab, readerSymtab);

        // Track refs.
        myWriterSymtab = writerSymtab;
        myReaderSymtab = readerSymtab;

        // Track modification
        myWriterSymtabMaxId = writerSymtab.getMaxId();
        myReaderSymtabMaxId = readerSymtab.getMaxId();

        return myResult;
    }
}