# icu_provider [![crates.io](https://img.shields.io/crates/v/icu_provider)](https://crates.io/crates/icu_provider) `icu_provider` is one of the [`ICU4X`] components. Unicode's experience with ICU4X's parent projects, ICU4C and ICU4J, led the team to realize that data management is the most critical aspect of deploying internationalization, and that it requires a high level of customization for the needs of the platform it is embedded in. As a result ICU4X comes with a selection of providers that should allow for ICU4X to naturally fit into different business and technological needs of customers. `icu_provider` defines traits and structs for transmitting data through the ICU4X locale data pipeline. The primary trait is [`DataProvider`]. It is parameterized by a [`KeyedDataMarker`], which contains the data type and a [`DataKey`]. It has one method, [`DataProvider::load`], which transforms a [`DataRequest`] into a [`DataResponse`]. - [`DataKey`] is a fixed identifier for the data type, such as `"plurals/cardinal@1"`. - [`DataRequest`] contains additional annotations to choose a specific variant of the key, such as a locale. - [`DataResponse`] contains the data if the request was successful. In addition, there are three other traits which are widely implemented: - [`AnyProvider`] returns data as `dyn Any` trait objects. - [`BufferProvider`] returns data as `[u8]` buffers. - [`DynamicDataProvider`] returns structured data but is not specific to a key. The most common types required for this crate are included via the prelude: ```rust use icu_provider::prelude::*; ``` ### Types of Data Providers All nontrivial data providers can fit into one of two classes. 1. [`AnyProvider`]: Those whose data originates as structured Rust objects 2. [`BufferProvider`]: Those whose data originates as unstructured `[u8]` buffers **✨ Key Insight:** A given data provider is generally *either* an [`AnyProvider`] *or* a [`BufferProvider`]. Which type depends on the data source, and it is not generally possible to convert one to the other. See also [crate::constructors]. #### AnyProvider These providers are able to return structured data cast into `dyn Any` trait objects. Users can call [`as_downcasting()`] to get an object implementing [`DataProvider`] by downcasting the trait objects. Examples of AnyProviders: - [`DatagenProvider`] reads structured data from CLDR source files and returns ICU4X data structs. - [`AnyPayloadProvider`] wraps a specific data struct and returns it. - The `BakedDataProvider` which encodes structured data directly in Rust source #### BufferProvider These providers are able to return unstructured data typically represented as [`serde`]-serialized buffers. Users can call [`as_deserializing()`] to get an object implementing [`DataProvider`] by invoking Serde Deserialize. Examples of BufferProviders: - [`FsDataProvider`] reads individual buffers from the filesystem. - [`BlobDataProvider`] reads buffers from a large in-memory blob. ### Provider Adapters ICU4X offers several built-in modules to combine providers in interesting ways. These can be found in the [`icu_provider_adapters`] crate. ### Testing Provider This crate also contains a concrete provider for demonstration purposes: - [`HelloWorldProvider`] returns "hello world" strings in several languages. If you need a testing provider that contains the actual resource keys used by ICU4X features, see the [`icu_testdata`] crate. ### 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`]. Data structs should generally have one lifetime argument: `'data`. This lifetime allows data structs to borrow zero-copy data. ### Data generation API *This functionality is enabled with the "datagen" Cargo feature* The [`datagen`] module contains several APIs for data generation. See [`icu_datagen`] for the reference data generation implementation. [`ICU4X`]: ../icu/index.html [`DataProvider`]: data_provider::DataProvider [`DataKey`]: key::DataKey [`DataLocale`]: request::DataLocale [`IterableDynamicDataProvider`]: datagen::IterableDynamicDataProvider [`IterableDataProvider`]: datagen::IterableDataProvider [`AnyPayloadProvider`]: ../icu_provider_adapters/any_payload/struct.AnyPayloadProvider.html [`HelloWorldProvider`]: hello_world::HelloWorldProvider [`AnyProvider`]: any::AnyProvider [`Yokeable`]: yoke::Yokeable [`impl_dynamic_data_provider!`]: impl_dynamic_data_provider [`icu_provider_adapters`]: ../icu_provider_adapters/index.html [`DatagenProvider`]: ../icu_datagen/struct.DatagenProvider.html [`as_downcasting()`]: AsDowncastingAnyProvider::as_downcasting [`as_deserializing()`]: AsDeserializingBufferProvider::as_deserializing [`CldrJsonDataProvider`]: ../icu_datagen/cldr/struct.CldrJsonDataProvider.html [`FsDataProvider`]: ../icu_provider_fs/struct.FsDataProvider.html [`BlobDataProvider`]: ../icu_provider_blob/struct.BlobDataProvider.html [`icu_testdata`]: ../icu_testdata/index.html [`icu_datagen`]: ../icu_datagen/index.html ## More Information For more information on development, authorship, contributing etc. please visit [`ICU4X home page`](https://github.com/unicode-org/icu4x).