Miscellaneous Details

String Encoding

  • All output strings are encoded in UTF-8.
  • Metadata files are written encoded in UTF-8.
  • Input strings are expected to be encoded in UTF-8.
  • Metadata files read are expected to be encoded in UTF-8.
  • File paths are case-sensitive if and only if the underlying file system is case-sensitive.

Language Codes

All language strings in the API are codes of the form ll or ll_CC, where ll is an ISO 639-1 language code and CC is an ISO 3166 country code. For example, the default language for metadata message content is English, identified by the code en, and Brazilian Portuguese is pt_BR.


All errors encountered are thrown as exceptions that inherit from std::exception.

Metadata Files

LOOT stores plugin metadata in YAML files. It distinguishes between masterlist and userlist files: each game has a single masterlist, which is a public, curated metadata store, and each LOOT user has a private userlist, which can contain metadata added by the user. The two files use the same syntax, but metadata in the userlist extends or replaces metadata sourced from the masterlist.

LOOT’s plugin metadata can be conditional, eg. a plugin may require a patch only if another plugin is also present. The API’s LoadLists() method parses metadata files into memory, but does not evaluate these conditions, so the loaded metadata may contain metadata that is invalid for the installed game that the loot::DatabaseInterface object being operated on was created for.

The EvalLists() must be called to evaluate any conditions in the loaded metadata. In doing so it discards any metadata with a condition that evaluates to false, but the pre-evaluation metadata is cached internally so that re-evaluation does not require the lists to be reloaded.


All unevaluated metadata is cached between calls to LoadLists(). Evaluated metadata is cached between calls to EvalLists(). Metadata conditions and their results are cached between calls to EvalLists(), so that every call to EvalLists() re-evaluates all conditions, but conditions that are used more than once in the loaded metadata are only evaluated once.

Plugin content is cached between calls to LoadPlugins() and SortPlugins().

Load order is cached on creation of a game using CreateGameHandle() and when SetLoadOrder() is called, and plugins’ active states are cached between calls to LoadPlugins() and SortPlugins().


Loading metadata lists is a relatively costly operation, as is updating the masterlist (which involves loading it). Evaluating the loaded metadata lists is not very costly relative to loading them, though is performance depends on the type and number of conditions used in the loaded metadata, and all the conditions involve filesystem access.

Sorting plugins is expensive, as it involves loading all the FormIDs for all the plugins, apart from the game’s main master file, which is skipped as an optimisation (it doesn’t depend on anything else and is much bigger than any other plugin, so is unnecessary and slow to load).

Getting plugin metadata once loaded is cheap, as is getting a masterlist’s revision.