-XBT_PUBLIC(size_t) MSG_file_read(void* ptr, size_t size, size_t nmemb,
- msg_file_t fd);
-XBT_PUBLIC(size_t) MSG_file_write(const void* ptr, size_t size, size_t nmemb,
- msg_file_t fd);
-XBT_PUBLIC(msg_file_t) MSG_file_open(const char* mount, const char* path);
+XBT_PUBLIC(size_t) MSG_file_read(size_t size, msg_file_t fd);
+XBT_PUBLIC(size_t) MSG_file_write(size_t size, msg_file_t fd);
+XBT_PUBLIC(msg_file_t) MSG_file_open(const char* mount, const char* path,
+ void* data);
+XBT_PUBLIC(void*) MSG_file_get_data(msg_file_t fd);
+XBT_PUBLIC(msg_error_t) MSG_file_set_data(msg_file_t fd, void * data);