add dummy ChannelFind implementation.

Since this class is not really used...

src/client/pv/pvAccess.h

@@ -385,6 +385,10 @@ public:
 
     virtual std::tr1::shared_ptr<ChannelProvider> getChannelProvider() = 0;
     virtual void cancel() = 0;
+
+    //! Allocate a no-op ChannelFind.  This is sufficient for most, if not all, ChannelProvider implementations.
+    //! Holds only a weak_ptr<ChannelProvider>
+    static ChannelFind::shared_pointer buildDummy(const std::tr1::shared_ptr<ChannelProvider>& provider);
 };
 
 /**

src/client/pvAccess.cpp

@@ -430,7 +430,6 @@ ChannelRequester::shared_pointer DefaultChannelRequester::build()
     return ret;
 }
 
-
 MonitorElement::MonitorElement(epics::pvData::PVStructurePtr const & pvStructurePtr)
     : pvStructurePtr(pvStructurePtr)
     ,changedBitSet(epics::pvData::BitSet::create(static_cast<epics::pvData::uint32>(pvStructurePtr->getNumberFields())))
@@ -438,3 +437,26 @@ MonitorElement::MonitorElement(epics::pvData::PVStructurePtr const & pvStructure
 {}
 
 }} // namespace epics::pvAccess
+
+namespace {
+
+struct DummyChannelFind : public epics::pvAccess::ChannelFind {
+    epics::pvAccess::ChannelProvider::weak_pointer provider;
+    DummyChannelFind(const epics::pvAccess::ChannelProvider::shared_pointer& provider) : provider(provider) {}
+    virtual ~DummyChannelFind() {}
+    virtual void destroy() OVERRIDE FINAL {}
+    virtual epics::pvAccess::ChannelProvider::shared_pointer getChannelProvider() OVERRIDE FINAL { return provider.lock(); }
+    virtual void cancel() OVERRIDE FINAL {}
+};
+
+}
+
+namespace epics {namespace pvAccess {
+
+ChannelFind::shared_pointer ChannelFind::buildDummy(const ChannelProvider::shared_pointer& provider)
+{
+    std::tr1::shared_ptr<DummyChannelFind> ret(new DummyChannelFind(provider));
+    return ret;
+}
+
+}} // namespace epics::pvAccess