X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=blobdiff_plain;f=ginac%2Fptr.h;h=c8b0691230bc5c8d8b8c49fc7f7d63620a2387c9;hp=fd380506fdd6daaec5183e94f8557c7306f51f4c;hb=6ff92476a4dcd32f9a0c6f59c95c74812ea86fef;hpb=6eedac996204ebc3355807d7f887b0c366cb3c07

diff --git a/ginac/ptr.h b/ginac/ptr.h
index fd380506..c8b06912 100644
--- a/ginac/ptr.h
+++ b/ginac/ptr.h
@@ -3,7 +3,7 @@
  *  Reference-counted pointer template. */
 
 /*
- *  GiNaC Copyright (C) 1999-2003 Johannes Gutenberg University Mainz, Germany
+ *  GiNaC Copyright (C) 1999-2008 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
@@ -17,12 +17,13 @@
  *
  *  You should have received a copy of the GNU General Public License
  *  along with this program; if not, write to the Free Software
- *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
 #ifndef __GINAC_PTR_H__
 #define __GINAC_PTR_H__
 
+#include <cstddef> // for size_t
 #include <functional>
 #include <iosfwd>
 
@@ -30,12 +31,28 @@
 
 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> >;
@@ -48,26 +65,29 @@ public:
     // 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)
+		// NB1: Must first add reference to "other", since other might be *this.
+		// NB2: Cache other.p, because if "other" is a subexpression of p,
+		//      deleting p will also invalidate "other".
+		T *otherp = other.p;
+		otherp->add_reference();
+		if (p->remove_reference() == 0)
 			delete p;
-		p = other.p;
+		p = otherp;
 		return *this;
 	}
 
@@ -80,10 +100,10 @@ public:
 	 *  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;
 		}
 	}
@@ -122,6 +142,7 @@ public:
 	inline friend std::ostream & operator<<(std::ostream & os, const ptr<T> & rhs)
 	{
 		os << rhs.p;
+		return os;
 	}
 
 private:
@@ -130,6 +151,7 @@ private:
 
 } // namespace GiNaC
 
+
 namespace std {
 
 /** Specialization of std::less for ptr<T> to enable ordering of ptr<T>