1 files changed, 107 insertions, 0 deletions
diff --git a/libmail/objectmonitor.H b/libmail/objectmonitor.H
new file mode 100644
index 0000000..f04233f
--- /dev/null
+++ b/libmail/objectmonitor.H
@@ -0,0 +1,107 @@
+/*
+** Copyright 2002, Double Precision Inc.
+**
+** See COPYING for distribution information.
+*/
+#ifndef libmail_objectmonitor_H
+#define libmail_objectmonitor_H
+
+///////////////////////////////////////////////////////////////////////////
+//
+// Helper class that detects when the object references by a ptr is destroyed.
+//
+// Subclass mail::obj.  Declare mail::ptr<T>, where T is mail::obj's
+// subclass.  After mail::obj is destroyed, mail::ptr<T>::operator T *()
+// will return NULL
+
+#include <set>
+#include <cstdio>
+
+#include "namespace.H"
+
+LIBMAIL_START
+
+class ptrBase {
+public:
+	ptrBase();
+	virtual ~ptrBase();
+	virtual void ptrDestroyed()=0;
+};
+
+template<class T> class ptr : public ptrBase {
+
+	T *r;
+
+public:
+	ptr(T *ptrArg) : r(NULL)
+	{
+		if (ptrArg)
+			ptrArg->objectBaseSet.insert(this);
+		r=ptrArg;
+	}
+
+	ptr(const ptr &o) : r(NULL)
+	{
+		(*this)=o;
+	}
+
+	ptr &operator=(const ptr &o)
+	{
+		if (o.r == NULL ||
+		    o.r->objectBaseSet.count(this) == 0)
+		{
+			if (o.r)
+				o.r->objectBaseSet.insert(this);
+
+			if (r && r->objectBaseSet.count(this) > 0)
+				r->objectBaseSet.erase(r->objectBaseSet
+						       .find(this));
+		}
+		r=o.r;
+
+		return *this;
+	}
+
+	~ptr()
+	{
+		if (r && r->objectBaseSet.count(this) > 0)
+			r->objectBaseSet.erase(r->objectBaseSet.find(this));
+	}
+
+	operator T *() const
+	{
+		return r;
+	}
+
+	T * operator->() const
+	{
+		return r;
+	}
+
+	bool isDestroyed() const { return r == 0; }
+
+	void ptrDestroyed() { r=NULL; }
+
+};
+
+// Some convenient macros
+
+#define MONITOR(T)  mail::ptr<T> thisMonitor(this)
+
+#define DESTROYED() ( thisMonitor.isDestroyed() )
+
+class obj {
+
+public:
+	std::set<ptrBase *> objectBaseSet;
+
+	obj();
+	virtual ~obj();
+
+	obj(const obj &);
+	obj &operator=(const obj &);
+};
+
+LIBMAIL_END
+
+#endif