Struct LanguageIdentifier

pub struct LanguageIdentifier {
    pub language: Language,
    pub script: Option<Script>,
    pub region: Option<Region>,
    pub variants: Variants,
}

A core struct representing a Unicode BCP47 Language Identifier.

Ordering

This type deliberately does not implement Ord or PartialOrd because there are multiple possible orderings. Depending on your use case, two orderings are available:

1. A string ordering, suitable for stable serialization: LanguageIdentifier::strict_cmp
2. A struct ordering, suitable for use with a BTreeSet: LanguageIdentifier::total_cmp

See issue: https://github.com/unicode-org/icu4x/issues/1215

Parsing

Unicode recognizes three levels of standard conformance for any language identifier:

• well-formed - syntactically correct
• valid - well-formed and only uses registered language, region, script and variant subtags…
• canonical - valid and no deprecated codes or structure.

At the moment parsing normalizes a well-formed language identifier converting _ separators to - and adjusting casing to conform to the Unicode standard.

Any syntactically invalid subtags will cause the parsing to fail with an error.

This operation normalizes syntax to be well-formed. No legacy subtag replacements is performed. For validation and canonicalization, see LocaleCanonicalizer.

Examples

Simple example:

use icu::locale::{
    langid,
    subtags::{language, region},
};

let li = langid!("en-US");

assert_eq!(li.language, language!("en"));
assert_eq!(li.script, None);
assert_eq!(li.region, Some(region!("US")));
assert_eq!(li.variants.len(), 0);

More complex example:

use icu::locale::{
    langid,
    subtags::{language, region, script, variant},
};

let li = langid!("eN-latn-Us-Valencia");

assert_eq!(li.language, language!("en"));
assert_eq!(li.script, Some(script!("Latn")));
assert_eq!(li.region, Some(region!("US")));
assert_eq!(li.variants.get(0), Some(&variant!("valencia")));

Fields

language: Language

Language subtag of the language identifier.

script: Option<Script>

Script subtag of the language identifier.

region: Option<Region>

Region subtag of the language identifier.

variants: Variants

Variant subtags of the language identifier.

Implementations

impl LanguageIdentifier

pub const UNKNOWN: Self

The unknown language identifier “und”.

pub const fn is_unknown(&self) -> bool

Whether this LanguageIdentifier equals LanguageIdentifier::UNKNOWN.

pub fn strict_cmp(&self, other: &[u8]) -> Ordering

Compare this LanguageIdentifier with BCP-47 bytes.

The return value is equivalent to what would happen if you first converted this LanguageIdentifier to a BCP-47 string and then performed a byte comparison.

This function is case-sensitive and results in a total order, so it is appropriate for binary search. The only argument producing Ordering::Equal is self.to_string().

Examples

Sorting a list of langids with this method requires converting one of them to a string:

use icu::locale::LanguageIdentifier;
use std::cmp::Ordering;
use writeable::Writeable;

// Random input order:
let bcp47_strings: &[&str] = &[
    "ar-Latn",
    "zh-Hant-TW",
    "zh-TW",
    "und-fonipa",
    "zh-Hant",
    "ar-SA",
];

let mut langids = bcp47_strings
    .iter()
    .map(|s| s.parse().unwrap())
    .collect::<Vec<LanguageIdentifier>>();
langids.sort_by(|a, b| {
    let b = b.write_to_string();
    a.strict_cmp(b.as_bytes())
});
let strict_cmp_strings = langids
    .iter()
    .map(|l| l.to_string())
    .collect::<Vec<String>>();

// Output ordering, sorted alphabetically
let expected_ordering: &[&str] = &[
    "ar-Latn",
    "ar-SA",
    "und-fonipa",
    "zh-Hant",
    "zh-Hant-TW",
    "zh-TW",
];

assert_eq!(expected_ordering, strict_cmp_strings);

pub fn total_cmp(&self, other: &Self) -> Ordering

Compare this LanguageIdentifier with another LanguageIdentifier field-by-field. The result is a total ordering sufficient for use in a BTreeSet.

Unlike LanguageIdentifier::strict_cmp, the ordering may or may not be equivalent to string ordering, and it may or may not be stable across ICU4X releases.

Examples

This method returns a nonsensical ordering derived from the fields of the struct:

use icu::locale::LanguageIdentifier;
use std::cmp::Ordering;

// Input strings, sorted alphabetically
let bcp47_strings: &[&str] = &[
    "ar-Latn",
    "ar-SA",
    "und-fonipa",
    "zh-Hant",
    "zh-Hant-TW",
    "zh-TW",
];
assert!(bcp47_strings.windows(2).all(|w| w[0] < w[1]));

let mut langids = bcp47_strings
    .iter()
    .map(|s| s.parse().unwrap())
    .collect::<Vec<LanguageIdentifier>>();
langids.sort_by(LanguageIdentifier::total_cmp);
let total_cmp_strings = langids
    .iter()
    .map(|l| l.to_string())
    .collect::<Vec<String>>();

// Output ordering, sorted arbitrarily
let expected_ordering: &[&str] = &[
    "ar-SA",
    "ar-Latn",
    "und-fonipa",
    "zh-TW",
    "zh-Hant",
    "zh-Hant-TW",
];

assert_eq!(expected_ordering, total_cmp_strings);

Use a wrapper to add a LanguageIdentifier to a BTreeSet:

use icu::locale::LanguageIdentifier;
use std::cmp::Ordering;
use std::collections::BTreeSet;

#[derive(PartialEq, Eq)]
struct LanguageIdentifierTotalOrd(LanguageIdentifier);

impl Ord for LanguageIdentifierTotalOrd {
    fn cmp(&self, other: &Self) -> Ordering {
        self.0.total_cmp(&other.0)
    }
}

impl PartialOrd for LanguageIdentifierTotalOrd {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

let _: BTreeSet<LanguageIdentifierTotalOrd> = unimplemented!();

pub fn normalizing_eq(&self, other: &str) -> bool

Compare this LanguageIdentifier with a potentially unnormalized BCP-47 string.

The return value is equivalent to what would happen if you first parsed the BCP-47 string to a LanguageIdentifier and then performed a structural comparison.

Examples

use icu::locale::LanguageIdentifier;

let bcp47_strings: &[&str] = &[
    "pl-LaTn-pL",
    "uNd",
    "UnD-adlm",
    "uNd-GB",
    "UND-FONIPA",
    "ZH",
];

for a in bcp47_strings {
    assert!(a.parse::<LanguageIdentifier>().unwrap().normalizing_eq(a));
}

impl LanguageIdentifier

pub fn to_string(&self) -> String

Converts the given value to a String.

Under the hood, this uses an efficient [Writeable] implementation. However, in order to avoid allocating a string, it is more efficient to use [Writeable] directly.

Trait Implementations

impl Clone for LanguageIdentifier

fn clone(&self) -> LanguageIdentifier

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LanguageIdentifier

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for LanguageIdentifier

This trait is implemented for compatibility with fmt!. To create a string, [Writeable::write_to_string] is usually more efficient.

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl From<&LanguageIdentifier> for (Language, Option<Script>, Option<Region>)

Convert from a LanguageIdentifier to an LSR tuple.

Examples

use icu::locale::{
    langid,
    subtags::{language, region, script},
};

let lid = langid!("en-Latn-US");
let (lang, script, region) = (&lid).into();

assert_eq!(lang, language!("en"));
assert_eq!(script, Some(script!("Latn")));
assert_eq!(region, Some(region!("US")));

fn from(langid: &LanguageIdentifier) -> Self

Converts to this type from the input type.

impl From<&LanguageIdentifier> for DataLocale

fn from(langid: &LanguageIdentifier) -> Self

Converts to this type from the input type.

impl From<&LanguageIdentifier> for LocalePreferences

fn from(lid: &LanguageIdentifier) -> Self

Converts to this type from the input type.

impl From<(Language, Option<Script>, Option<Region>)> for LanguageIdentifier

Convert from an LSR tuple to a LanguageIdentifier.

Examples

use icu::locale::{
    langid,
    subtags::{language, region, script},
    LanguageIdentifier,
};

let lang = language!("en");
let script = script!("Latn");
let region = region!("US");
assert_eq!(
    LanguageIdentifier::from((lang, Some(script), Some(region))),
    langid!("en-Latn-US")
);

fn from(lsr: (Language, Option<Script>, Option<Region>)) -> Self

Converts to this type from the input type.

impl From<Language> for LanguageIdentifier

Examples

use icu::locale::{langid, subtags::language, LanguageIdentifier};

assert_eq!(LanguageIdentifier::from(language!("en")), langid!("en"));

fn from(language: Language) -> Self

Converts to this type from the input type.

impl From<LanguageIdentifier> for DataLocale

fn from(langid: LanguageIdentifier) -> Self

Converts to this type from the input type.

impl From<LanguageIdentifier> for Locale

fn from(id: LanguageIdentifier) -> Self

Converts to this type from the input type.

impl From<Locale> for LanguageIdentifier

fn from(loc: Locale) -> Self

Converts to this type from the input type.

impl From<Option<Region>> for LanguageIdentifier

Examples

use icu::locale::{langid, subtags::region, LanguageIdentifier};

assert_eq!(
    LanguageIdentifier::from(Some(region!("US"))),
    langid!("und-US")
);

fn from(region: Option<Region>) -> Self

Converts to this type from the input type.

impl From<Option<Script>> for LanguageIdentifier

Examples

use icu::locale::{langid, subtags::script, LanguageIdentifier};

assert_eq!(
    LanguageIdentifier::from(Some(script!("latn"))),
    langid!("und-Latn")
);

fn from(script: Option<Script>) -> Self

Converts to this type from the input type.

impl Hash for LanguageIdentifier

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for LanguageIdentifier

fn eq(&self, other: &LanguageIdentifier) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Writeable for LanguageIdentifier

fn write_to<W: Write + ?Sized>(&self, sink: &mut W) -> Result

Writes a string to the given sink. Errors from the sink are bubbled up. The default implementation delegates to write_to_parts, and discards any Part annotations.

fn writeable_length_hint(&self) -> LengthHint

Returns a hint for the number of UTF-8 bytes that will be written to the sink.

fn write_to_parts<S>(&self, sink: &mut S) -> Result<(), Error>

where S: PartsWrite + ?Sized,

Write bytes and Part annotations to the given sink. Errors from the sink are bubbled up. The default implementation delegates to write_to, and doesn’t produce any Part annotations.

fn write_to_string(&self) -> Cow<'_, str>

Creates a new String with the data from this Writeable. Like ToString, but smaller and faster.

impl Eq for LanguageIdentifier

impl StructuralPartialEq for LanguageIdentifier