2 files changed, 42 insertions, 17 deletions

diff --git a/cpp/src/qpid/amqp_0_10/Holder.h b/cpp/src/qpid/amqp_0_10/Holder.h
index 4c1fccd44f..1664afcc8f 100644
--- a/cpp/src/qpid/amqp_0_10/Holder.h
+++ b/cpp/src/qpid/amqp_0_10/Holder.h
@@ -27,29 +27,36 @@
 namespace qpid {
 namespace amqp_0_10 {
 
+using framing::in_place;
+
+template <class Invokable> struct InvokeVisitor {
+    typedef void result_type;
+    Invokable& target;     
+    InvokeVisitor(Invokable& i) : target(i) {}
+
+    template <class Action>
+    void operator()(const Action& action) { action.invoke(target); }
+};
+
 template <class DerivedHolder, class BaseHeld, size_t Size>
-struct Holder : public framing::Blob<Size, BaseHeld> {
+class Holder : public framing::Blob<Size, BaseHeld> {
     typedef framing::Blob<Size, BaseHeld> Base;
-    
-    struct Assign : public ApplyFunctor<void> {
-        Holder& holder;
-        Assign(Holder& x) : holder(x) {}
-        template <class T> void operator()(const T& rhs) { holder=rhs; }
-    };
 
+  public:
+    
     Holder() {}
-    Holder(const BaseHeld& x) { *this=x; }
-    template <class T> Holder(const T& value) : Base(value) {}
+    template <class T> explicit Holder(const T& value) : Base(value) {}
 
     using Base::operator=;
-    Holder& operator=(const BaseHeld& rhs) {
-        Assign assign(*this);
-        apply(assign, rhs);
-        return *this;
-    }
+    Holder& operator=(const BaseHeld& rhs);
     
     uint8_t getCode() const { return this->get()->getCode(); }
     uint8_t getClassCode() const { return this->get()->getClassCode(); }
+
+    template <class Invokable> void invoke(Invokable& i) const {
+        InvokeVisitor<Invokable> v(i);
+        apply(v, *this->get());
+    }
     
     template <class S> void encode(S& s) const {
         s(getClassCode())(getCode());
@@ -65,8 +72,23 @@ struct Holder : public framing::Blob<Size, BaseHeld> {
         s.split(*this);
         apply(s, *this->get());
     }
+
+  private:
+    struct Assign : public ApplyFunctor<void> {
+        Holder& holder;
+        Assign(Holder& x) : holder(x) {}
+        template <class T> void operator()(const T& rhs) { holder=rhs; }
+    };
 };
 
+template <class D, class B, size_t S>
+Holder<D,B,S>& Holder<D,B,S>::operator=(const B& rhs) {
+    Assign assign(*this);
+    apply(assign, rhs);
+    return *this;
+}
+
+
 
 }} // namespace qpid::amqp_0_10
 
diff --git a/cpp/src/qpid/amqp_0_10/Unit.h b/cpp/src/qpid/amqp_0_10/Unit.h
index bcba36e35a..0229e07419 100644
--- a/cpp/src/qpid/amqp_0_10/Unit.h
+++ b/cpp/src/qpid/amqp_0_10/Unit.h
@@ -34,15 +34,12 @@
 namespace qpid {
 namespace amqp_0_10 {
 
-
 /**
  * A Unit contains a frame header and associated value.
  * For all types except BODY the frame header is for a complete segment.
  */
 class Unit {
   public:
-    typedef boost::variant<ControlHolder, CommandHolder, Header, Body> Variant;
-
     explicit Unit(const FrameHeader& h=FrameHeader()) : header(h) { updateVariant(); }
 
     /**
@@ -57,12 +54,18 @@ class Unit {
     template<class T> const T* get() const { return boost::get<T>(&variant); }
     template<class T> T* get() { return boost::get<T>(&variant); }
     template<class T> Unit& operator=(const T& t) { variant=t; return *this; }
+
+    template <class V> typename V::result_type applyVisitor(V& v) const {
+        variant.apply_visitor(v); 
+    }
     
     template <class S> void serialize(S& s) { variant.apply_visitor(s); s.split(*this); }
     template <class S> void encode(S&) const {} 
     template <class S> void decode(S&) { updateHeader(header.getFlags()); }
 
   private:
+    typedef boost::variant<ControlHolder, CommandHolder, Header, Body> Variant;
+
     void updateHeader(uint8_t flags);
     void updateVariant();