package umontreal.iro.lecuyer.util;

/**
 * Extends the {@link AbstractChrono}  class to compute the global CPU time used
 * by the Java Virtual Machine. This includes CPU time taken by any thread,
 * including the garbage collector, class loader, etc.
 * 
 * 

 * Part of this class is implemented in the C language and the 
 * implementation is unfortunately operating system-dependent.
 * The C functions for the current class have been compiled on a 32-bit machine
 * running Linux. For a platform-independent CPU timer (valid only with Java-1.5 or later),
 *  one should use the class {@link ThreadCPUTimeChrono} which is programmed 
 * directly in Java.
 * 
 */
public class GlobalCPUTimeChrono extends AbstractChrono {
   
   private static boolean ssjUtilLoaded = false;
   private static native void Heure (long[] tab);

   protected void getTime (long[] tab) {
      if (!ssjUtilLoaded) {
         // We cannot load the library in a static block
         // since the subclass ChronoSingleThread does not
         // need the native method.
         System.loadLibrary ("ssjutil");

         ssjUtilLoaded = true;
      }
      
      Heure (tab);
   }



   /**
    * Constructs a Chrono object and initializes it to zero.
    * 
    */
   public GlobalCPUTimeChrono() {
      init();
   }

}