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Concourse is a self-tuning database that is designed for both ad hoc analytics and high volume transactions at scale. Developers use Concourse to quickly build mission critical software while also benefiting from real time insight into their most important data. With Concourse, end-to-end data management requires no extra infrastructure, no prior configuration and no additional coding–all of which greatly reduce costs and allow developers to focus on core business problems.

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/*
 * Copyright (c) 2013-2019 Cinchapi Inc.
 *
 * 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.cinchapi.concourse.time;

import java.util.concurrent.atomic.AtomicLong;

/**
 * A clock that gives as close to the current time as possible without
 * duplicates in microseconds.
 * 
 * @author Jeff Nelson
 * 
 */
public class AtomicClock {

    private final AtomicLong time = new AtomicLong();

    /**
     * Get the current timestamp (in microseconds), which is guaranteed to be
     * unique.
     * 
     * @return the timestamp.
     */
    public long time() {
        long now = System.currentTimeMillis() * 1000;
        for (;;) {
            long lastTime = time.get();
            if(lastTime >= now) {
                now = lastTime + 1;
            }
            if(time.compareAndSet(lastTime, now)) {
                return now;
            }
        }
    }
}