--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Sources/PythonModule.cpp	Thu Mar 26 18:47:01 2020 +0100
@@ -0,0 +1,116 @@
+/**
+ * Python plugin for Orthanc
+ * Copyright (C) 2017-2020 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 "PythonModule.h"
+
+#include "PythonString.h"
+
+#include <OrthancPluginCppWrapper.h>
+
+#include <boost/thread/mutex.hpp>
+#include <set>
+
+
+#if PY_VERSION_HEX < 0x03070000 /* 3.7.0 */
+static PythonObject* GetModule(PythonLock& lock,
+                               const std::string& utf8Name)
+{
+  static boost::mutex           mutex_;
+  static std::set<std::string>  loadedModules_;
+
+  boost::mutex::scoped_lock l(mutex_);
+
+  if (loadedModules_.find(utf8Name) == loadedModules_.end())
+  {
+    PythonString tmp(lock, utf8Name);
+
+    // The module is not imported yet
+    loadedModules_.insert(utf8Name);
+    return new PythonObject(lock, PyImport_Import(tmp.GetPyObject()), false);
+  }
+  else
+  {
+    // PyImport_AddModule returns a borrowed reference
+    return new PythonObject(lock, PyImport_AddModule(utf8Name.c_str()), true);
+  }
+}
+
+#else
+// The "PyImport_GetModule()" function was introduced in Python
+// 3.7.0
+static PythonObject* GetModule(PythonLock& lock,
+                               const std::string& utf8Name)
+{
+  PythonString tmp(lock, utf8Name);
+
+  PyObject* module = PyImport_GetModule(tmp.GetPyObject());
+  if (module != NULL)
+  {
+    // The module was already imported by a previous call: Reuse it
+    return new PythonObject(lock, module);
+  }
+  else
+  {
+    // This is the first time this module is used: Import it
+    return new PythonObject(lock, PyImport_Import(tmp.GetPyObject()));
+  }
+}
+#endif
+  
+
+PythonModule::PythonModule(PythonLock& lock,
+                           const std::string& utf8Name) :
+  lock_(lock),
+  name_(utf8Name)
+{
+  module_.reset(GetModule(lock, utf8Name));
+}
+
+
+bool PythonModule::IsValid() const
+{
+  return (module_.get() != NULL &&
+          module_->IsValid());
+}
+
+
+PythonObject& PythonModule::GetObject() const
+{
+  if (!IsValid())
+  {
+    ORTHANC_PLUGINS_THROW_EXCEPTION(BadSequenceOfCalls);
+  }
+  else
+  {
+    return *module_;
+  }
+}
+
+
+PyObject* PythonModule::GetPyObject() const
+{
+  if (!IsValid())
+  {
+    ORTHANC_PLUGINS_THROW_EXCEPTION(BadSequenceOfCalls);
+  }
+  else
+  {
+    return module_->GetPyObject();
+  }
+}