PropertyOrdinalMapVisitor.java

/*
 * Copyright 2007-2012 Amazon Technologies, Inc. or its affiliates.
 * Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
 * of Amazon Technologies, 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.
 * 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 com.amazon.carbonado.cursor;

import java.util.IdentityHashMap;
import java.util.Map;

import com.amazon.carbonado.Storable;

import com.amazon.carbonado.filter.ExistsFilter;
import com.amazon.carbonado.filter.PropertyFilter;
import com.amazon.carbonado.filter.Visitor;

/**
 * Visits a filter and maps all property filters to their zero-based ordinal
 * position.
 *
 * @author Brian S O'Neill
 */
class PropertyOrdinalMapVisitor<S extends Storable> extends Visitor<S, Object, Object> {
    private int mOrdinal;
    private Map<PropertyFilter, Integer> mOrdinalMap;

    PropertyOrdinalMapVisitor() {
        mOrdinalMap = new IdentityHashMap<PropertyFilter, Integer>();
    }

    public Map<PropertyFilter, Integer> getPropertyOrdinalMap() {
        return mOrdinalMap;
    }

    @Override
    public Object visit(PropertyFilter filter, Object param) {
        mOrdinalMap.put(filter, mOrdinal++);
        return null;
    }

    @Override
    public Object visit(ExistsFilter filter, Object param) {
        return filter.getSubFilter().accept(this, param);
    }
}