ZMuseCount.h

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#ifndef ZMUSECOUNT_H
#define ZMUSECOUNT_H
 
 
// ----------------------------------------------------------------------
//
//  ZMuseCount.h - utility class for use in reference-counting
//
//
//  History:
//    19-Sep-1997  WEB  Design stolen, and code adapted, from pp 70-73 of
//      Koenig & Moo: "Ruminations on C++" (1996)
//
// ----------------------------------------------------------------------
 
 
class ZMuseCount  {
 
public:
 
  // --------------------------
  // Constructors & destructor:
  // --------------------------
 
  ZMuseCount();
    // Constructor
  ZMuseCount( const ZMuseCount & u );
    // Copy constructor
  ~ZMuseCount();
    // Destructor
 
 
  // -----------------------------------
  // Functions useful to a handle class:
  // -----------------------------------
 
  bool only();
    // Is there exactly one copy of the referent?
 
  bool makeonly();
    // Enables the handle (to a ClassType) to refer to a unique (copy of)
    // the referent via the following usage:
    //   if ( u.makeonly() )            /* ZMuseCount u;     */
    //      p = new ClassType( *p );    /* ClassType * p;  */
    // This is useful in implementing copy-on-write semantics
    // (i.e., non-shared or value semantics), and would appear just before
    // updating (any part of) *p in such a context.
 
  bool reattach( const ZMuseCount & u );
    // Simplifies a handle's implementation of assignment via the following
    // usage:
    //   if ( u.reattach(h.u) )       /* Handle<ClassType> h; */
    //     delete p;                  /* p and u as above     */
    //   p = h.p;
 
 
private:
 
  int * p;
    // *p is the reference counter itself
 
  ZMuseCount & operator=( const ZMuseCount & );
    // Forbidden operation on a ZMuseCount object
 
};  // ZMuseCount
 
 
//#include "CLHEP/RefCount/ZMuseCount.icc"
 
 
#endif  // ZMUSECOUNT_H