#cldr #icu #unicode #localization #provider


Trait and struct definitions for the ICU data provider

4 releases (breaking)

0.4.0 Nov 2, 2021
0.3.0 Jul 29, 2021
0.2.0 Apr 29, 2021
0.1.0 Oct 15, 2020

#9 in Internationalization (i18n)

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icu_provider crates.io

icu_provider is one of the ICU4X components.

It defines traits and structs for transmitting data through the ICU4X locale data pipeline. The primary trait is DataProvider. It has one method, which transforms a Request into a Response:

fn load_payload(&self, req: &DataRequest) -> Result<DataResponse<'data>, DataError>

A Request contains a ResourceKey (a composition of a Category and sub-category, e.g., "plurals/cardinal@1") and ResourceOptions (a language identifier and optional variant, e.g., "fr") being requested. The Response contains the data payload corresponding to the Request.

A Response contains a [DataPayload] along with other metadata.

The most common types required for ICU4X DataProvider are included via the prelude:

use icu_provider::prelude::*;

Concrete Implementations of Data Providers

Any object implementing DataProvider can be used to supply ICU4X with locale data. ICU4X ships with some pre-built data providers:

  • CldrJsonDataProvider reads structured data directly from CLDR source files.
  • FsDataProvider reads structured data from the filesystem. It can also write out that filesystem structure. More efficient than CldrJsonDataProvider.

This crate also contains some concrete implementations for testing purposes:

Types and Lifetimes

Types compatible with Yokeable can be passed through the data provider, so long as they are associated with a marker type implementing [DataMarker].

Most DataProvider traits take one lifetime argument: 'data. This lifetime allows data structs to borrow zero-copy data. In practice, it also represents the lifetime of data that the Cart of the Yoke of the DataPayload borrows; for more information on carts and yokes, see [yoke].

Additional Traits


Data providers can implement IterableDataProvider, allowing iteration over all ResourceOptions instances supported for a certain key in the data provider.

For more information, see the [iter] module.


Enabled with the "provider_serde" feature

The trait SerdeDeDataProvider removes the type argument from DataProvider and requires that all data structs be deserializable via Serde. This allows for a Serde-enabled provider to be saved as a trait object without being specific to a data struct type.

DataProvider<dyn SerdeSeDataStruct>

Enabled with the "provider_serde" feature

Data providers capable of returning opaque SerdeSeDataStruct trait objects can be used as input to a data exporter, such as when writing data to the filesystem.

This trait is normally implemented using the impl_dyn_provider! macro.

DataProvider<dyn ErasedDataStruct>

The trait ErasedDataProvider removes the type argument from DataProvider and requires that all data structs be convertible to the Any type. This enables the processing of data without the caller knowing the underlying data struct.

Since ErasedDataProvider is not specific to a single type, it can be useful for caches or other bulk data operations.

This trait is normally implemented using the impl_dyn_provider! macro.

More Information

For more information on development, authorship, contributing etc. please visit ICU4X home page.


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