getFileSize API for fsfw

unittests/mocks/FilesystemMock.cpp

@@ -145,3 +145,13 @@ ReturnValue_t FilesystemMock::getBaseFilename(FilesystemParams params, char *nam
 }
 
 bool FilesystemMock::isDirectory(const char *path) { return false; }
+
+bool FilesystemMock::getFileSize(FilesystemParams params, size_t &fileSize) {
+  std::string filename(params.path);
+  auto iter = fileMap.find(filename);
+  if (iter == fileMap.end()) {
+    fileSize = iter->second.fileRaw.size();
+    return true;
+  }
+  return false;
+}