flower/handle.hh

   1 #ifndef HANDLE_HH
   2 #define HANDLE_HH
   3
   4 /// reference counting handle
   5 template<class T>
   6 class Handle {
   7     T *obj;
   8     int *refs;
   9
  10     /// let go of ref. Delete if necessary
  11     void down() {
  12         if (!(*refs--)) {
  13             delete obj;
  14             delete refs;
  15         }
  16         obj = 0;
  17         refs = 0;
  18     }
  19     /// point to new object.
  20     void up(T *t, int *r) {
  21         if (!r) {
  22             refs = new int;
  23             *refs = 1;
  24         } else {
  25             refs =r;
  26             *refs++;
  27         }
  28         obj = t;
  29     }
  30     /// POST: *refs == 1
  31     void copy() {
  32         if(*refs != 1){
  33             T * newobj = new T(*obj );
  34             down();
  35             up(newobj);
  36         }
  37     }
  38     Handle(Handle const &src) {
  39         up(src.obj, src.refs);
  40     }
  41     Handle(T & o) {
  42         up (&o);
  43     }
  44     void operator=(Handle const& src) {
  45         if (this == &src)
  46             return;
  47         down();
  48         up(src.o, src.refs);
  49     }
  50     operator const T&() {
  51         return *obj;
  52     }
  53     operator T&() {
  54         copy();
  55         return *obj;
  56     }
  57 }
  58 #endif