--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Sources/ICallbackRegistration.cpp	Thu Jun 10 18:19:27 2021 +0200
@@ -0,0 +1,68 @@
+/**
+ * Python plugin for Orthanc
+ * Copyright (C) 2020-2021 Osimis S.A., Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Affero General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Affero General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+
+#include "ICallbackRegistration.h"
+
+#include "../Resources/Orthanc/Plugins/OrthancPluginCppWrapper.h"
+#include "PythonLock.h"
+
+PyObject *ICallbackRegistration::Apply(ICallbackRegistration& registration,
+                                       PyObject* args,
+                                       PyObject*& singletonCallback,
+                                       const std::string& details)
+{
+  // https://docs.python.org/3/extending/extending.html#calling-python-functions-from-c
+  PyObject* callback = NULL;
+
+  if (!PyArg_ParseTuple(args, "O", &callback) ||
+      callback == NULL)
+  {
+    const std::string message = "Expected a callback function to register one " + details;
+    PyErr_SetString(PyExc_ValueError, message.c_str());
+    return NULL;
+  }
+  else if (singletonCallback != NULL)
+  {
+    const std::string message = "Can only register one " + details;
+    PyErr_SetString(PyExc_RuntimeError, message.c_str());
+    return NULL;
+  }
+  else
+  {
+    OrthancPlugins::LogInfo("Registering one " + details);
+    registration.Register();
+    
+    singletonCallback = callback;
+    Py_XINCREF(singletonCallback);
+  
+    Py_INCREF(Py_None);
+    return Py_None;
+  }
+}
+
+
+void ICallbackRegistration::Unregister(PyObject*& singletonCallback)
+{
+  PythonLock lock;
+        
+  if (singletonCallback != NULL)
+  {
+    Py_XDECREF(singletonCallback);
+  }
+}