The resource class

The class resource has the following interface :

   interface resource 
   {
      resource(double a);          // constructor
   
      int report(histogram* h,double interval = 0);  // generate report
   
      void reset();                // reset amount left to initial
   
      void release(double a = 1);  // release amount left by a
      void acquire(double a = 1);  // acquire a from amount left
   
      int available(double a = 1); // is an amount a available ?

      int full();                  // is full ?
      int empty();                 // is empty ?
      double left();               // how much left ?
      double used();               // how much used ?
      double occupied();           // returns occupation (%).
   
      friend ostream& operator<<(ostream& os,resource& r);
   };

The resource class also has a report method. When invoked a histogram is filled with samples of the occupation of the resource.