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EST_THandle.h
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/* Centre for Speech Technology Research */
/* University of Edinburgh, UK */
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#ifndef __EST_THANDLE_H__
#define __EST_THANDLE_H__
#include <iostream>
using namespace std;
#include "EST_bool.h"
/** A `smart' pointer which does reference counting.
*
* Behaves almost like a pointer as far as naive code is concerned, but
* keeps count of how many handles are holding on to the contents
* and deletes it when there are none.
*
* You need to be careful there are no dumb C++ pointers to things which
* are being handled this way.
*
* Things to be handled should implement the same interface as EST_Handleable
* (either by taking that as a superclass or by reimplementing it) and in
* addition define {\tt object_ptr()}. See EST_TBox for an example.
*
* There are two parameter types. In most cases the thing which contains the
* reference count and the data it represents will be the same object, but
* in the case of boxed values it may not be, so you can specify the type
* of both independently.
*
* @see EST_Handleable
* @see EST_TBox
* @see EST_THandle:example
*
* @author Richard Caley <rjc@cstr.ed.ac.uk>
* @version $Id: EST_THandle.h,v 1.5 2006/07/19 21:52:12 awb Exp $
*/
template<class BoxT, class ObjectT>
class EST_THandle {
private:
BoxT *ptr;
public:
EST_THandle(void) { ptr = (BoxT *)NULL; }
EST_THandle(BoxT *p) { if ((ptr=p)) p->inc_refcount(); }
EST_THandle(const EST_THandle &cp) {
ptr=cp.ptr;
if (ptr)
ptr->inc_refcount();
}
~EST_THandle(void) {
if (ptr)
ptr->dec_refcount();
if (ptr && ptr->is_unreferenced())
delete ptr;
}
bool null() const { return ptr == NULL; }
int shareing(void) const { return ptr?(ptr->refcount() > 1):0; }
EST_THandle &operator = (EST_THandle h) {
// doing it in this order means self assignment is safe.
if (h.ptr)
(h.ptr)->inc_refcount();
if (ptr)
ptr->dec_refcount();
if (ptr && ptr->is_unreferenced())
delete ptr;
ptr=h.ptr;
return *this;
}
// If they manage to get hold of one...
// Actually usually used to assign NULL and so (possibly) deallocate
// the object currently pointed to.
EST_THandle &operator = (BoxT *t_ptr) {
// doing it in this order means self assignment is safe.
if (t_ptr)
t_ptr->inc_refcount();
if (ptr)
ptr->dec_refcount();
if (ptr && ptr->is_unreferenced())
delete ptr;
ptr=t_ptr;
return *this;
}
operator ObjectT *() {
return ptr?(ptr->object_ptr()):(ObjectT *)NULL;
}
operator const ObjectT *() const {
return ptr?(ptr->object_ptr()):(const ObjectT *)NULL;
}
int operator == (const BoxT *p) const { return ptr == p; }
int operator != (const BoxT *p) const { return !(*this == p); }
const ObjectT& operator *() const { return *(ptr->object_ptr()); }
ObjectT& operator *() { return *(ptr->object_ptr()); }
const ObjectT* operator ->() const { return (ptr->object_ptr()); }
ObjectT* operator ->() { return (ptr->object_ptr()); }
friend int operator == (const EST_THandle< BoxT, ObjectT > &a, const EST_THandle< BoxT, ObjectT > & b)
{return a.ptr==b.ptr; }
friend int operator != (const EST_THandle< BoxT, ObjectT > &a, const EST_THandle< BoxT, ObjectT > & b)
{ return !( a==b ); }
friend ostream & operator << (ostream &s, const EST_THandle< BoxT, ObjectT > &a)
{ return s << "HANDLE"; }
};
#endif