Added PyDetector (#677)

* Added PyDetector. Refactored PyMatcher.

* Fixed python freezing with multi-threading

corelib/src/python/PythonInterface.cpp

@@ -0,0 +1,119 @@
+/*
+ * PythonSingleTon.h
+ *
+ *  Created on: Jan. 14, 2021
+ *      Author: mathieu
+ */
+
+#include <rtabmap/core/PythonInterface.h>
+#include <rtabmap/utilite/ULogger.h>
+#include <rtabmap/utilite/UThread.h>
+
+namespace rtabmap {
+
+UMutex PythonInterface::mutex_;
+int PythonInterface::refCount_ = 0;
+PyThreadState * PythonInterface::mainThreadState_ = 0;
+unsigned long PythonInterface::mainThreadID_ = 0;
+
+PythonInterface::PythonInterface() :
+		threadState_(0)
+{
+	UScopeMutex lockM(mutex_);
+	if(refCount_ == 0)
+	{
+		// initialize Python
+		Py_Initialize();
+
+		// initialize thread support
+		PyEval_InitThreads();
+		Py_DECREF(PyImport_ImportModule("threading"));
+
+		//release the GIL, store thread state, set the current thread state to NULL
+		mainThreadState_ = PyEval_SaveThread();
+		UASSERT(mainThreadState_);
+		mainThreadID_ = UThread::currentThreadId();
+	}
+
+	++refCount_;
+}
+
+PythonInterface::~PythonInterface()
+{
+	UScopeMutex lock(mutex_);
+	if(refCount_>0 && --refCount_==0)
+	{
+		// shut down the interpreter
+		PyEval_RestoreThread(mainThreadState_);
+		Py_Finalize();
+	}
+}
+
+void PythonInterface::lock()
+{
+	mutex_.lock();
+
+	if(UThread::currentThreadId() == mainThreadID_)
+	{
+		PyEval_RestoreThread(mainThreadState_);
+	}
+	else
+	{
+		// create a thread state object for this thread
+		threadState_ = PyThreadState_New(mainThreadState_->interp);
+		UASSERT(threadState_);
+		PyEval_RestoreThread(threadState_);
+	}
+}
+
+void PythonInterface::unlock()
+{
+	if(UThread::currentThreadId() == mainThreadID_)
+	{
+		mainThreadState_ = PyEval_SaveThread();
+	}
+	else
+	{
+		PyThreadState_Clear(threadState_);
+		PyThreadState_DeleteCurrent();
+	}
+	mutex_.unlock();
+}
+
+std::string PythonInterface::getTraceback()
+{
+	// Author: https://stackoverflow.com/questions/41268061/c-c-python-exception-traceback-not-being-generated
+
+	PyObject* type;
+	PyObject* value;
+	PyObject* traceback;
+
+	PyErr_Fetch(&type, &value, &traceback);
+	PyErr_NormalizeException(&type, &value, &traceback);
+
+	std::string fcn = "";
+	fcn += "def get_pretty_traceback(exc_type, exc_value, exc_tb):\n";
+	fcn += "    import sys, traceback\n";
+	fcn += "    lines = []\n";
+	fcn += "    lines = traceback.format_exception(exc_type, exc_value, exc_tb)\n";
+	fcn += "    output = '\\n'.join(lines)\n";
+	fcn += "    return output\n";
+
+	PyRun_SimpleString(fcn.c_str());
+	PyObject* mod = PyImport_ImportModule("__main__");
+	UASSERT(mod);
+	PyObject* method = PyObject_GetAttrString(mod, "get_pretty_traceback");
+	UASSERT(method);
+	PyObject* outStr = PyObject_CallObject(method, Py_BuildValue("OOO", type, value, traceback));
+	std::string pretty;
+	if(outStr)
+		pretty = PyBytes_AsString(PyUnicode_AsASCIIString(outStr));
+
+	Py_DECREF(method);
+	Py_DECREF(outStr);
+	Py_DECREF(mod);
+
+	return pretty;
+}
+
+}