Documentation
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Overview ¶
Package langtag is the single shared language-tag helper for Ether.
It exists so subtitles, trackprefs, plex and the transcode probes do not drift apart with private copies of the same normalisation: a tag is parsed as BCP 47 (primary, optional script, optional region), folded to a canonical comparable form, and matched by tier.
Index ¶
Constants ¶
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Variables ¶
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Functions ¶
func MatchTier ¶
MatchTier scores a wanted language against a track language, both normalised with Normalize:
- 3: exact (pt-br × pt-br, pt × pt, por × pt after normalising);
- 2: generic want × regional track (pt × pt-br, zh × zh-tw) — a generic preference accepts any region of the language;
- 1: regional want × generic track (pt-br × pt, zh-tw × zh) — accepted, but weak: it never beats tier 3 or 2 for the same want;
- 0: different languages, regions that differ (pt-br × pt-pt, zh-cn × zh-tw), or an empty/invalid side.
Because only pt/zh keep a region after normalising, script is never mistaken for region here: zh-TW × zh-Hant-TW both fold to zh-tw (3).
func Normalize ¶
Normalize folds a language tag to its canonical comparable form: the primary subtag, plus the region only for Portuguese and Chinese (pt-br vs pt-pt and zh-cn vs zh-tw are distinct languages to every consumer; en-GB and en-US are not). The script is discarded, except that for Chinese a script without an explicit region implies one by convention: zh-Hans -> zh-cn, zh-Hant -> zh-tw (an explicit region always wins: zh-Hant-CN -> zh-cn). "pob" folds to "pt-br", ISO 639-2 primaries to ISO 639-1, and empty, invalid or undetermined tags to "".
Types ¶
type Tag ¶
Tag is a parsed BCP 47 tag. Primary is canonical: known ISO 639-2 codes fold to their ISO 639-1 form ("eng" -> "en", "por" -> "pt"), and the legacy OpenSubtitles code "pob" parses as primary "pt" with region "br". Script and Region are lower-case and empty when absent.
func ParseBCP47 ¶
ParseBCP47 parses a BCP 47 tag into primary, script and region.
The region is the 2-letter or 3-digit subtag that follows the optional 4-letter script subtag — never the script itself, so "zh-Hant-TW" yields primary "zh", script "hant", region "tw" (taking the second subtag as the region would read "hant" and lose "tw"). Variant and extension subtags after the region are validated but not reported. Garbage — empty subtags, a primary that is not 2-3 ASCII letters, stray short subtags — is rejected (ok is false).
Source Files