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https://github.com/loot/libloot.git
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Oliver Hamlet
4ffd784d87
Use ISO language codes directly instead, which has the advantage that new languages can be used in metadata without having up update the API to support them. Closes #5.
80 lines
3.4 KiB
ReStructuredText
80 lines
3.4 KiB
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*********************
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Miscellaneous Details
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*********************
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String Encoding
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===============
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* All output strings are encoded in UTF-8.
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* Metadata files are written encoded in UTF-8.
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* Input strings are expected to be encoded in UTF-8.
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* Metadata files read are expected to be encoded in UTF-8.
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* File paths are case-sensitive if and only if the underlying file system is
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case-sensitive.
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Language Codes
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==============
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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``.
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Errors
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======
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All errors encountered are thrown as exceptions that inherit from
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``std::exception``.
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Metadata Files
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==============
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LOOT stores plugin metadata in YAML files. It distinguishes between *masterlist*
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and *userlist* files: each game has a single masterlist, which is a public,
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curated metadata store, and each LOOT user has a private userlist, which can
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contain metadata added by the user. The two files use the same syntax, but
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metadata in the userlist extends or replaces metadata sourced from the
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masterlist.
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LOOT's plugin metadata can be conditional, eg. a plugin may require a patch only
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if another plugin is also present. The API's :cpp:func:`LoadLists` method parses
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metadata files into memory, but does not evaluate these conditions, so the
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loaded metadata may contain metadata that is invalid for the installed game that
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the :cpp:class:`loot::DatabaseInterface` object being operated on was created for.
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The :cpp:func:`EvalLists` must be called to evaluate any conditions in the
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loaded metadata. In doing so it discards any metadata with a condition that
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evaluates to false, but the pre-evaluation metadata is cached internally so that
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re-evaluation does not require the lists to be reloaded.
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Caching
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=======
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All unevaluated metadata is cached between calls to :cpp:func:`LoadLists`.
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Evaluated metadata is cached between calls to :cpp:func:`EvalLists`. Metadata
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conditions and their results are cached between calls to :cpp:func:`EvalLists`,
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so that every call to :cpp:func:`EvalLists` re-evaluates all conditions, but
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conditions that are used more than once in the loaded metadata are only
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evaluated once.
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Plugin content is cached between calls to :cpp:func:`LoadPlugins` and
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:cpp:func:`SortPlugins`.
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Load order is cached on creation of a game using :cpp:func:`CreateGameHandle`
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and when :cpp:func:`SetLoadOrder` is called, and plugins' active states are
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cached between calls to :cpp:func:`LoadPlugins` and :cpp:func:`SortPlugins`.
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Performance
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===========
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Loading metadata lists is a relatively costly operation, as is updating the
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masterlist (which involves loading it). Evaluating the loaded metadata lists is
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not very costly relative to loading them, though is performance depends on the
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type and number of conditions used in the loaded metadata, and all the
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conditions involve filesystem access.
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Sorting plugins is expensive, as it involves loading all the FormIDs for all
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the plugins, apart from the game's main master file, which is skipped as an
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optimisation (it doesn't depend on anything else and is much bigger than any
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other plugin, so is unnecessary and slow to load).
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Getting plugin metadata once loaded is cheap, as is getting a masterlist's
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revision.
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