comparison PyExtensionManager.h @ 37:27bab3a16c9a vampy2final

new branch Vampy2final

+/*
+
+ * Vampy : This plugin is a wrapper around the Vamp plugin API.
+ * It allows for writing Vamp plugins in Python.
+
+ * Centre for Digital Music, Queen Mary University of London.
+ * Copyright (C) 2008-2009 Gyorgy Fazekas, QMUL. (See Vamp sources 
+ * for licence information.)
+
+*/
+
+/*
+PyExtensionManager: This class is responsible for initialisation
+and cleanup of the extension module, as well as the loaded plugin
+module namespaces. 
+
+NOTES: Why do we need to clean up the module?
+
+The module exposed by Vampy to the embedded interpreter contains 
+callback functions. These functions are accessed via function 
+pointers stored in the extension module's namespace dictionary.
+
+Unfortunately, when the shared library is unloaded and reloaded 
+during a host session, these addresses might change. 
+Therefore, we reinitialise the module dict before each use. 
+However, this will cause garbage collection errors or segmentation 
+faults, when elements of the dict of the previous session are 
+attempted to free. Therefore, we clear the dictinary describing
+the module namespace and replace all fuction pointers with Py_None
+objects in individual plugin module namespaces. The reference
+count on these can be safely decremented next time vampy is loaded
+and the namespaces are reinitialised.
+
+Why doesn't the GC clean this up correctly?
+
+In a normal Python session the GC would deallocate the module
+dict at the end. In embedded python, although the GC appears
+to be called when the shared lib is unloaded, the interpreter
+is reused. Since there is no C/API call to unload modules,
+and at the time of unloading vampy the wrapped function pointers
+are still valid, the GC doesn't collect them, nor are they freed
+by the interpreter. When vampy is reloaded however, the module
+dict will contain invalid addresses. The above procedure solves
+this problem.
+
+
+*/
+
+
+#ifndef _PYEXTENSIONMANAGER_H_
+#define _PYEXTENSIONMANAGER_H_
+
+using std::cerr;
+using std::endl;
+using std::string;
+using std::vector;
+
+class PyExtensionManager
+{
+public:
+	PyExtensionManager();
+	~PyExtensionManager();
+	bool initExtension();
+	void setPlugModuleNames(vector<string> pyPlugs);
+	void deleteModuleName(string plugKey);
+
+private:
+	static char* m_exposedNames[];
+	
+	vector<string> m_plugModuleNames;
+	PyObject* m_pyGlobalNamespace;
+	PyObject* m_pyVampyNamespace;
+
+	void cleanAllLocals() const;
+	void cleanLocalNamespace(const char* plugModuleName) const;
+	void updateAllLocals() const;
+	void updateLocalNamespace(const char* plugModuleName) const;
+
+	void printDict(PyObject* inDict) const;
+	bool cleanModule() const;
+
+};
+
+#endif
+
+