Slight changes to LADSPAInfo class

SpiralSound/Plugins/LADSPAPlugin/LADSPAInfo.C

@@ -85,10 +85,6 @@ LADSPAInfo::RescanPlugins(void)
 		cerr << m_Plugins.size() << " plugins found in " << m_Libraries.size() << " libraries" << endl;
 	}
 
-// No last loaded library or plugin
-	m_LastLoadedLibraryIndex = m_Libraries.size();
-	m_LastLoadedPluginIndex = m_Plugins.size();
-
 // Sort list by name
 	sort(m_OrderedPluginList.begin(), m_OrderedPluginList.end(), PluginEntrySortAsc());
 
@@ -115,29 +111,12 @@ LADSPAInfo::UnloadAllLibraries(void)
 	for (vector<LibraryInfo>::iterator i = m_Libraries.begin();
 	     i != m_Libraries.end(); i++) {
 		if (i->Handle) dlclose(i->Handle);
-	}
-
-// No last loaded library or plugin
-	m_LastLoadedLibraryIndex = m_Libraries.size();
-	m_LastLoadedPluginIndex = m_Plugins.size();
-}
-
-void
-LADSPAInfo::UnloadLibraryByID(unsigned long unique_id)
-{
-	if (m_IDLookup.find(unique_id) == m_IDLookup.end()) {
-		cerr << "LADSPA Plugin ID " << unique_id << " not found!" << endl;
-	} else {
-
-	// Get plugin index
-		unsigned long plugin_index = m_IDLookup[unique_id];
-		UnloadLibraryByPlugin(plugin_index);
+		i->RefCount = 0;
 	}
 }
 
 const LADSPA_Descriptor *
-LADSPAInfo::GetDescriptorByID(unsigned long unique_id,
-                              bool unload_previous_library)
+LADSPAInfo::GetDescriptorByID(unsigned long unique_id)
 {
 	if (m_IDLookup.find(unique_id) == m_IDLookup.end()) {
 		cerr << "LADSPA Plugin ID " << unique_id << " not found!" << endl;
@@ -148,20 +127,55 @@ LADSPAInfo::GetDescriptorByID(unsigned long unique_id,
 	unsigned long plugin_index = m_IDLookup[unique_id];
 
 	PluginInfo *pi = &(m_Plugins[plugin_index]);
+	LibraryInfo *li = &(m_Libraries[pi->LibraryIndex]);
+
 	if (!(pi->Descriptor)) {
 		LADSPA_Descriptor_Function desc_func = GetDescriptorFunctionForLibrary(pi->LibraryIndex);
 
-		if (desc_func) {
-			pi->Descriptor = desc_func(pi->Index);
+		if (desc_func) pi->Descriptor = desc_func(pi->Index);
+	}
+	
+	if (pi->Descriptor) {
+	// Success, so increment ref counter for library
+		li->RefCount++;
+	}
+
+	return pi->Descriptor;
+}
+
+void
+LADSPAInfo::DiscardDescriptorByID(unsigned long unique_id)
+{
+	if (m_IDLookup.find(unique_id) == m_IDLookup.end()) {
+		cerr << "LADSPA Plugin ID " << unique_id << " not found!" << endl;
+	} else {
+
+	// Get plugin index
+		unsigned long plugin_index = m_IDLookup[unique_id];
 
-		// Unload previously loaded library (if different)
-			if ((m_LastLoadedLibraryIndex != m_Libraries.size()) &&
-				(m_LastLoadedLibraryIndex != pi->LibraryIndex)) {
-				UnloadLibraryByPlugin(plugin_index);
+		PluginInfo *pi = &(m_Plugins[plugin_index]);
+		LibraryInfo *li = &(m_Libraries[pi->LibraryIndex]);
+
+	// Decrement reference counter for library, and unload if last
+		if (li->RefCount > 0) {
+			li->RefCount--;
+			if (li->RefCount == 0) {
+				dlclose(li->Handle);
+			// Need to unset all plugin descriptors that may have been
+			// set from this library
+			// Plugins in library will be a contiguous block, so we
+			// just check each direction from given plugin
+				unsigned long i = plugin_index - 1;
+				while (m_Plugins[i].LibraryIndex == pi->LibraryIndex) {
+					m_Plugins[i--].Descriptor = NULL;
+				}
+				i = plugin_index + 1;
+				while (m_Plugins[i].LibraryIndex == pi->LibraryIndex) {
+					m_Plugins[i++].Descriptor = NULL;
+				}
 			}
 		}
 	}
-	return pi->Descriptor;
 }
 
 unsigned long
@@ -503,25 +517,3 @@ LADSPAInfo::GetDescriptorFunctionForLibrary(unsigned long library_index)
 
 	return desc_func;
 }
-
-void
-LADSPAInfo::UnloadLibraryByPlugin(unsigned long plugin_index)
-{
-// Unload library corresponding to given plugin index
-	PluginInfo *pi = &(m_Plugins[plugin_index]);
-	LibraryInfo *li = &(m_Libraries[pi->LibraryIndex]);
-	if (li->Handle) dlclose(li->Handle);
-
-// Need to unset all plugin descriptors that may have been
-// set from this library
-// Plugins in library will be a contiguous block, so we
-// just check each direction from given plugin
-	unsigned long i = plugin_index - 1;
-	while (m_Plugins[i].LibraryIndex == pi->LibraryIndex) {
-		m_Plugins[i--].Descriptor = NULL;
-	}
-	i = plugin_index + 1;
-	while (m_Plugins[i].LibraryIndex == pi->LibraryIndex) {
-		m_Plugins[i++].Descriptor = NULL;
-	}
-}

SpiralSound/Plugins/LADSPAPlugin/LADSPAInfo.h

@@ -38,22 +38,36 @@ public:
 	// Unload all loaded plugins and clean up
 	~LADSPAInfo();
 
-	// Rescan all paths in $LADSPA_PATH, as per constructor
-	// This will also unload all libraries
+	// ************************************************************************
+	// Loading/Unloading plugin libraries
+	//
+	// At first, no library dlls are loaded.
+	//
+	// Each library has an associated reference count, which is initially 0.
+	// As descriptors are requested, using GetDescriptorByID, this count
+	// is incremented. The library dll is loaded on the first request.
+	// At descriptors are discarded, the count is decremented, and when this
+	// reaches 0, the library is unloaded.
+
+	// Rescan all paths in $LADSPA_PATH, as per constructor.
+	// This will also unload all libraries, and make any descriptors that
+	// have not been discarded with DiscardDescriptorByID invalid.
 	void                            RescanPlugins(void);
 
-	// Unload all dlopened libraries
+	// Unload all dlopened libraries. This will make any descriptors that
+	// have not been discarded with DiscardDescriptorByID invalid.
 	void                            UnloadAllLibraries(void);
 
-	// Unload library containing plugin id
-	void                            UnloadLibraryByID(unsigned long unique_id);
+	// Get descriptor of plugin with given ID. This increments the descriptor
+	// count for the corresponding library.
+	const LADSPA_Descriptor        *GetDescriptorByID(unsigned long unique_id);
 
-	// Get descriptor of plugin in list, loading library if necessary
-	// and optionally unloading previously loaded library (if different
-	// from library containing requested plugin. Phew!)
-	const LADSPA_Descriptor        *GetDescriptorByID(unsigned long unique_id,
-	                                                  bool unload_previous_library);
+	// Notify that a descriptor corresponding to the given ID has been
+	// discarded. This decrements the descriptor count for the corresponding
+	// library.
+	void                            DiscardDescriptorByID(unsigned long unique_id);
 
+	// Get unique ID of plugin identified by given library filename and label.
 	unsigned long                   GetIDFromFilenameAndLabel(std::string filename,
 	                                                          std::string label);
 
@@ -81,12 +95,12 @@ private:
 	void                            ExaminePath(const char *path);
 	bool                            CheckPlugin(LADSPA_Descriptor_Function desc_func);
 	LADSPA_Descriptor_Function      GetDescriptorFunctionForLibrary(unsigned long library_index);
-	void                            UnloadLibraryByPlugin(unsigned long plugin_index);
 
 	struct LibraryInfo
 	{
 		unsigned long           PathIndex;  // Index of path in m_Paths
 		std::string             Basename;   // Filename
+		unsigned long           RefCount;   // Count of descriptors requested from library
 		void                   *Handle;     // DLL Handle, NULL
 	};
 
@@ -121,9 +135,6 @@ private:
 	std::vector<LibraryInfo>        m_Libraries;
 	std::vector<PluginInfo>         m_Plugins;
 
-	unsigned long                   m_LastLoadedLibraryIndex;
-	unsigned long                   m_LastLoadedPluginIndex;
-
 	IDMap                           m_IDLookup;
 	StringMap                       m_FilenameLookup;
 

SpiralSound/Plugins/LADSPAPlugin/LADSPAPlugin.C

@@ -767,13 +767,13 @@ bool LADSPAPlugin::SelectPlugin(unsigned long UniqueID)
 // Reject trivial case
 	if (UniqueID == 0) return false;
 
-	m_PlugDesc = m_LADSPAInfo->GetDescriptorByID(UniqueID, true);
+	m_PlugDesc = m_LADSPAInfo->GetDescriptorByID(UniqueID);
 
 	if (m_PlugDesc) {
 	// Create instance
 		if (!(m_PlugInstHandle = m_PlugDesc->instantiate(m_PlugDesc, m_HostInfo->SAMPLERATE))) {
 			cerr << "WARNING: Could not instantiate plugin " << UniqueID << endl;
-			m_LADSPAInfo->UnloadLibraryByID(UniqueID);
+			m_LADSPAInfo->DiscardDescriptorByID(UniqueID);
 			m_PlugDesc = 0;
 			return false;
 		}
@@ -884,6 +884,8 @@ void LADSPAPlugin::ClearPlugin(void)
 		if (m_PlugDesc->deactivate) m_PlugDesc->deactivate(m_PlugInstHandle);
 		m_PlugDesc->cleanup(m_PlugInstHandle);
 		m_PlugDesc = NULL;
+
+		m_LADSPAInfo->DiscardDescriptorByID(m_UniqueID);
 	}
 
 	m_TabIndex = 1;