2 unstable releases

0.2.0 Jun 9, 2021
0.1.0 Jun 6, 2021

#117 in Internationalization (i18n)

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LCID-rs: A Rust library for Windows Language Code Identifiers and other language/culture information

crates.io docs.rs GitHub CI

[Repository] [Documentation] [Crate Registry (crates.io)]

This crate provides language code identifier parsing and information according to the [MS-LCID] Windows Language Code Identifier (LCID) Reference and System.Globalization.CultureInfo API.

The following information is provided:

  • Language Code Identifier/LCID (lcid), and lookup by LCID
  • Name/IETF language tag (name), and lookup by name
  • A non-localised, English readable language name (english_name)
  • ISO 639-1 two-letter code (iso639_two_letter)
  • ISO 639-2/639-3 three-letter code (iso639_three_letter)
  • The Windows API three-letter language code (windows_three_letter)
  • ANSI code page (ansi_code_page)

To use this crate, add the following to your Cargo.toml:

lcid = "0.2"

Language identifiers/information can be queried by Language Code Identifier (LCID, a 32-bit unsigned integer), name (a string, i.e. supported IETF BCP 47 language tags), or by directly referring to the language identifier constant:

use lcid::LanguageId;
use std::convert::TryInto;

fn main() {
    let lang: &LanguageId = 1033.try_into().unwrap();
    println!("Lang is '{}'/{}/'{}'", lang.name, lang.lcid, lang.english_name);

    let lang: &LanguageId = "en-US".try_into().unwrap();
    println!("Lang is '{}'/{}/'{}'", lang.name, lang.lcid, lang.english_name);

    let lang: &LanguageId = lcid::constants::LANG_EN_US;
    println!("Lang is '{}'/{}/'{}'", lang.name, lang.lcid, lang.english_name);

This prints the following for each:

Lang is 'en-US'/1033/'English (United States)'

Project name and status

I struggle to find a good name for this. "locale-info" might be misleading (might imply some kind of POSIX locale support), or "culture-info" implying more than the project offers (like calendar information). In the end, I chose "lcid-rs", because "lcid" is ambiguous/hard to search for, although I named the crate itself "lcid" because in the context of Rust, "lcid" is not ambiguous. It'd be nice if this project was referred to as "lcid-rs" in ambiguous contexts (linking to the repo, blog posts, etc), and "lcid" only in Rust code/configuration.

The maintenance status is "as-is". I'm happy to accept pull requests for corrections (as long as they align with MS-LCID and the Windows API), pull requests for new features, and pull requests for new MS-LCID protocol revisions in the future.

MS-LCID protocol revision

This library currently tracks the 14.1/2021-07-04 protocol revision. Future protocol revisions will may only trigger a minor version bump, so if you need lookup behaviour of a specific revision, pin this crate accordingly.


[0.2.0] - 2021-06-08

  • Tracks MS-LCID 14.1/2021-07-04 protocol revision
  • Provide ANSI code page information
  • Move LanguageId constants to a module, to avoid cluttering the crate namespace (breaking change)
  • Codegen: Sort languages by LCID and name, so the generated code is stable for languages that share an LCID (0x1000 ones)

[0.1.0] - 2021-06-06

  • Initial release

How the information was generated

First, information was extracted from the MS-LCID PDF, and from both HTML tables of the associated LCIDs ("numbered") and the unassociated LCIDs ("named"). This was then manually cleaned, converted to JSON, and compared.

Then, the GetCultureInfo.ps1 script was run on a Windows Server 2019 machine (Build 17763) to gather further information from the System.Globalization.CultureInfo API. The values returned by the API do not always match the information in MS-LCID, so some fix-up were applied. For details, please see the script.

Finally, the lcid-gen crate generates code for the lcid crate (src/gen.rs). This is done to avoid having a build-time dependency on the JSON files.

MS-LCID errata

Protocol revision 14.1/2021-07-04

  • "es-CU" is listed twice. Once as 0x5C0A in the "Language ID" table, and once in the "Locale Names without LCIDs" table as 0x1000. The former LCID was used.
  • "ff-Latn-GM" is misprinted as "ff-latn-GM" (lower-case "l"). This was corrected.


Licensed under either of

at your option.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.


~27K SLoC