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Dynamic Loading Overview

Source: qar-streaming-c/examples/dynamic_loading.c. See also Static linking vs. dynamic loading for the ABI rationale.

Dynamic Loading Overview

What You Will Learn​

  • Parse command-line arguments to locate the shared library
  • Dynamically load qar-streaming-c at runtime
  • Initialize and tear down the global library state

Prerequisites​

  • Build the SDK and locate the produced qar-streaming-c shared library
  • Ensure runtime binaries sit next to the library (default assumption)

Build and Run​

 cmake --build --preset x64-windows-debug --target dynamic_loading
 ./build/x64-windows/Debug/dynamic_loading.exe <path-to-qar-streaming-c.dll> [runtime-dir]

Parse Arguments​

Obtain the shared-library path and optional runtime directory.

  if(argc < 2)
  {
  print_usage(argv[0]);
  return 1;
  }
 
  const char* library_path = argv[1];
  const char* runtime_dir = NULL;
  char runtime_dir_buffer[1024] = { 0 };
 
  if(argc >= 3)
  {
  runtime_dir = argv[2];
  }
  else if(get_dir_from_path(library_path, runtime_dir_buffer, sizeof(runtime_dir_buffer)))
  {
  runtime_dir = runtime_dir_buffer;
  }

Load the Shared Library​

Use qar_library_load to dynamically load the DLL/SO/Dylib.

  printf("Loading qar-streaming-c from: %s\n", library_path);
  if(!qar_library_load(library_path))
  {
  fprintf(stderr, "Failed to load '%s'. Ensure the path is correct.\n", library_path);
  return 2;
  }

Initialize and Shutdown​

Initialize global state with qar_library_init, then destroy and unload when done.

  QarLibraryInit library_init = qar_library_init_default();
  library_init.enable_console_logging = true;
  library_init.log_folder_path = NULL; // Console logging is sufficient for this tutorial
 
  QarResult init_result = qar_library_init(&library_init);
  if(qar_result_is_error(init_result))
  {
  log_result("qar_library_init", init_result);
  qar_library_unload();
  return 3;
  }
 
  printf("Library initialized. Runtime binaries directory: %s\n", runtime_dir ? runtime_dir : "(derived from library path)");
 
  QarResult destroy_result = qar_library_destroy();
  log_result("qar_library_destroy", destroy_result);
 
  qar_library_unload();
  printf("Library unloaded. Dynamic loading tutorial complete.\n");

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