* Reference-counted pointer template. */
/*
- * GiNaC Copyright (C) 1999-2003 Johannes Gutenberg University Mainz, Germany
+ * GiNaC Copyright (C) 1999-2004 Johannes Gutenberg University Mainz, Germany
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
#ifndef __GINAC_PTR_H__
#define __GINAC_PTR_H__
+#include <cstddef> // for size_t
#include <functional>
#include <iosfwd>
namespace GiNaC {
+
+/** Base class for reference-counted objects. */
+class refcounted {
+public:
+ refcounted() throw() : refcount(0) {}
+
+ size_t add_reference() throw() { return ++refcount; }
+ size_t remove_reference() throw() { return --refcount; }
+ size_t get_refcount() const throw() { return refcount; }
+ void set_refcount(size_t r) throw() { refcount = r; }
+
+private:
+ size_t refcount; ///< reference counter
+};
+
+
/** Class of (intrusively) reference-counted pointers that support
* copy-on-write semantics.
*
* Requirements for T:
- * T::refcount member that supports ++refcount, --refcount, refcount = 1,
- * refcount == 0 and refcount > 1
+ * must support the refcounted interface (usually by being derived
+ * from refcounted)
* T* T::duplicate() member function (only if makewriteable() is used) */
template <class T> class ptr {
friend class std::less< ptr<T> >;
// no default ctor: a ptr is never unbound
/** Bind ptr to newly created object, start reference counting. */
- ptr(T *t) throw() : p(t) { GINAC_ASSERT(p); p->refcount = 1; }
+ ptr(T *t) throw() : p(t) { GINAC_ASSERT(p); p->set_refcount(1); }
/** Bind ptr to existing reference-counted object. */
- explicit ptr(T &t) throw() : p(&t) { ++p->refcount; }
+ explicit ptr(T &t) throw() : p(&t) { p->add_reference(); }
- ptr(const ptr & other) throw() : p(other.p) { ++p->refcount; }
+ ptr(const ptr & other) throw() : p(other.p) { p->add_reference(); }
~ptr()
{
- if (--p->refcount == 0)
+ if (p->remove_reference() == 0)
delete p;
}
ptr &operator=(const ptr & other)
{
- // NB: must first increment other.p->refcount, since other might be *this.
- ++other.p->refcount;
- if (--p->refcount == 0)
+ // NB: must first add reference to "other", since other might be *this.
+ other.p->add_reference();
+ if (p->remove_reference() == 0)
delete p;
p = other.p;
return *this;
* This ensures that the object is not shared by any other ptrs. */
void makewritable()
{
- if (p->refcount > 1) {
+ if (p->get_refcount() > 1) {
T *p2 = p->duplicate();
- p2->refcount = 1;
- --p->refcount;
+ p2->set_refcount(1);
+ p->remove_reference();
p = p2;
}
}
} // namespace GiNaC
+
namespace std {
/** Specialization of std::less for ptr<T> to enable ordering of ptr<T>