com.andrewkroh.cisco.common.TestUtils.java Source code

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Here is the source code for com.andrewkroh.cisco.common.TestUtils.java

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/*
 * Copyright 2013 Andrew Kroh
 *
 * 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.andrewkroh.cisco.common;

import io.netty.util.NetUtil;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

/**
 * Utility class for testing.
 *
 * @author akroh
 */
public class TestUtils {
    private static final int START_PORT = 32768;
    private static final int END_PORT = 65536;
    private static final int NUM_CANDIDATES = END_PORT - START_PORT;

    private static final List<Integer> PORTS = new ArrayList<Integer>();
    private static Iterator<Integer> portIterator;

    static {
        for (int i = START_PORT; i < END_PORT; i++) {
            PORTS.add(i);
        }
        Collections.shuffle(PORTS);
    }

    private static int nextCandidatePort() {
        if (portIterator == null || !portIterator.hasNext()) {
            portIterator = PORTS.iterator();
        }
        return portIterator.next();
    }

    /**
     * Return a free port which can be used to bind to
     *
     * @return port
     */
    public static int getFreePort() {
        for (int i = 0; i < NUM_CANDIDATES; i++) {
            int port = nextCandidatePort();
            try {
                // Ensure it is possible to bind on both wildcard and loopback.
                ServerSocket ss;
                ss = new ServerSocket();
                ss.setReuseAddress(false);
                ss.bind(new InetSocketAddress(port));
                ss.close();

                ss = new ServerSocket();
                ss.setReuseAddress(false);
                ss.bind(new InetSocketAddress(NetUtil.LOCALHOST, port));
                ss.close();

                return port;
            } catch (IOException e) {
                // ignore
            }
        }

        throw new RuntimeException("unable to find a free port");
    }
}