/*
 * 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
 *
 *   https://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 org.apache.bcel;

public class NanoTimer {

    private long timeNanos;

    public void reset() {
        timeNanos = 0;
    }

    public NanoTimer start() {
        timeNanos -= System.nanoTime();
        return this;
    }

    public void stop() {
        timeNanos += System.nanoTime();
    }

    public void subtract(final NanoTimer o) {
        timeNanos -= o.timeNanos;
    }

    /**
     * May ony be called after stop has been called as many times as start.
     */
    @Override
    public String toString() {
        return (double) timeNanos / 1000000000 + " s";
    }

}
