distributedlog-service/src/main/java/com/twitter/distributedlog/service/balancer/LimitedStreamChooser.java

/**
 * 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 com.twitter.distributedlog.service.balancer;

public class LimitedStreamChooser implements StreamChooser {

    public static LimitedStreamChooser of(StreamChooser underlying, int limit) {
        return new LimitedStreamChooser(underlying, limit);
    }

    final StreamChooser underlying;
    int limit;

    LimitedStreamChooser(StreamChooser underlying, int limit) {
        this.underlying = underlying;
        this.limit = limit;
    }

    @Override
    public synchronized String choose() {
        if (limit <= 0) {
            return null;
        }
        String s = underlying.choose();
        if (s == null) {
            limit = 0;
            return null;
        }
        --limit;
        return s;
    }
}