From 2fa3509533e164c318941b52a604f559924d7775 Mon Sep 17 00:00:00 2001
From: Konrad Rosenbaum <konrad@silmor.de>
Date: Sat, 24 Mar 2012 20:23:12 +0100
Subject: [PATCH] enhance shared dptr: allow decoupling

---
 dptr/dptr_base.h   |   14 +++++++++++++-
 dptr/dptr_shared.h |    6 +++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/dptr/dptr_base.h b/dptr/dptr_base.h
index 85f2e52..0342909 100644
--- a/dptr/dptr_base.h
+++ b/dptr/dptr_base.h
@@ -94,7 +94,19 @@ The d-pointer class Private is only forward declared, you have to fully declare
 Warning: shared d-pointers are not thread safe and they are only re-entrant if instances sharing the same d-pointer are only located in one thread, while instances with different d-pointers may be spread over different threads.
 
 \param dp name of the d-pointer*/
-#define DECLARE_SHARED_DPTR(dp) DECLARE_DPTR(dp)
+#define DECLARE_SHARED_DPTR(dp) \
+ private:\
+ class Private; \
+ class DPrivate{\
+  public:DPrivate();DPrivate(const DPrivate&);~DPrivate();\
+  DPrivate&operator=(const DPrivate&);\
+  const Private*operator->()const{return d;}\
+  Private*operator->(){return d;}\
+  DPrivate clone()const;\
+  void decouple();\
+  private:Private*d;\
+ }; \
+ DPrivate dp;
 
 
 #ifdef DECLARE_NONCOPY_DPTR
diff --git a/dptr/dptr_shared.h b/dptr/dptr_shared.h
index 88dc7a4..e7c49bf 100644
--- a/dptr/dptr_shared.h
+++ b/dptr/dptr_shared.h
@@ -32,6 +32,8 @@ class SharedDPtr
 		virtual void attach(){cnt++;}
 		///called by the wrapper to detach from an instance
 		virtual void detach(){cnt--;if(cnt==0)delete this;}
+		///called by the wrapper to enable copy-on-write logic
+		int currentRefCount()const{return cnt;}
 };
 
 //hide the namespace
@@ -58,5 +60,7 @@ To be used in implementation where the actual d-pointer class is implemented.
  Class::DPrivate::~DPrivate(){d->detach();}\
  Class::DPrivate Class::DPrivate::clone()const{DPrivate r;*(r.d)=*d;return r;}\
  Class::DPrivate& Class::DPrivate::operator=(const DPrivate&dp)\
- {if(d!=dp.d){d->detach();d=dp.d;d->attach();}return *this;}
+ {if(d!=dp.d){d->detach();d=dp.d;d->attach();}return *this;}\
+ void Class::DPrivate::decouple()\
+ {if(d->currentRefCount()>1){Private *p=new Class::Private(*d);d->detach();d=p;}}
 
-- 
1.7.2.5