icu_provider

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]:

rust 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.

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

rust 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:

• [InvariantDataProvider] returns fixed data that does not vary by locale.
• [StructProvider] wraps a particular instance of a struct and returns it.
• [HelloWorldProvider] returns "hello world" strings in several languages.

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

IterableDataProvider

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.

SerdeDeDataProvider

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.