// $Header: /home/cvs/jakarta-jmeter/src/jorphan/org/apache/jorphan/timer/HRTimer.java,v 1.4 2004/02/11 23:57:23 sebb Exp $
/*
 * Copyright 2002-2004 The Apache Software Foundation.
 *
 * 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 org.apache.jorphan.timer;

/**
 * A package-private implementation of {@link ITimer} based around native
 * getTime method. It will work on any platform for which a JNI
 * implementation of "hrtlib" library is available.
 
 * 
 * {@link TimerFactory} acts as the Factory for this class.

 * 
 * MT-safety: an instance of this class is safe to be used within the same
 * thread only.
 * 
 * @author Vlad Roubtsov
 * @author Originally published in JavaWorld
 * @version $Revision: 1.4 $
 */
final class HRTimer extends AbstractTimer 
{
    private static final String HRTIMER_LIB = "hrtlib";
    
    static
    {
        try
        {
            System.loadLibrary (HRTIMER_LIB);
        }
        catch (UnsatisfiedLinkError e)
        {
            System.out.println ("native lib '" + HRTIMER_LIB
                + "' not found in 'java.library.path': "
                + System.getProperty ("java.library.path"));
            
            throw e; // re-throw
        }
    }

    /*
     * This is supposed to return a fractional count of milliseconds elapsed
     * since some indeterminate moment in the past. The exact starting point
     * is not relevant because this timer class reports time differences only.
     * 
     * JNI code in HRTIMER_LIB library is supposed to implement this.
     */
    private static native double getTime ();

    protected double getCurrentTime()
    {
        return getTime();
    }    
}