icu_codepointtrie_builder

icu_codepointtrie_builder is a utility crate of the ICU4X project.

This crate exposes functionality to build a CodePointTrie from values provided at runtime. Because it is normally expected for CodePointTrie data to be pre-compiled, this crate is not optimized for speed; it should be used during a build phase.

Under the hood, this crate uses the CodePointTrie builder code from ICU4C, UMutableCPTrie. For more context, see https://github.com/unicode-org/icu4x/issues/1837.

Unlike most of ICU4X, due in large part to the native dependency, this crate is not guaranteed to be panic-free.

Build configuration

This crate has two primary modes it can be used in: "wasm" and "icu4c", exposed as Cargo features. If both are enabled, the code will internally use the wasm codepath.

The "wasm" mode uses a Wasm module packaged into this Rust crate that contains pre-compiled ICU4C CodePointTrie builder code. It evaluates the Wasm module using the Wasmer runtime, which "just works", but it requires a large number of Rust/Cargo dependencies.

The "icu4c" mode reduces the number of Rust dependencies, but it requires having a local copy of ICU4C available. To configure "icu4c" mode in Cargo, set the following environment variables:

• Set ICU4C_LIB_PATH to a directory full of ICU4C static or shared libraries.
• Set ICU4C_LINK_STATICALLY to any value to use the static libraries.
• Set ICU4C_RENAME_VERSION to the integer ICU4C version if ICU4C has renaming enabled. By default, we attempt to link non-renamed symbols.

If using dynamic linking, at runtime, you may need to set [DY]LD_LIBRARY_PATH to the ICU4C_LIB_PATH.

If not using Cargo, make sure to pass ICU4C_LIB_PATH to the linker via -L, link against icuuc, icui18n and icudata via -l flags, and set --cfg icu4c_enable_renaming if you need renamed ICU4C symbols.

Examples

use icu::collections::codepointtrie::CodePointTrie;
use icu::collections::codepointtrie::TrieType;
use icu_codepointtrie_builder::CodePointTrieBuilder;
use icu_codepointtrie_builder::CodePointTrieBuilderData;

let default_value = 1;
let error_value = 2;
let values_by_code_point = &[3, 4, 5, 6];

let cpt: CodePointTrie<u8> = CodePointTrieBuilder {
    data: CodePointTrieBuilderData::ValuesByCodePoint(values_by_code_point),
    default_value,
    error_value,
    trie_type: TrieType::Small,
}
.build();

assert_eq!(cpt.get32(0), 3);
assert_eq!(cpt.get32(1), 4);
assert_eq!(cpt.get32(2), 5);
assert_eq!(cpt.get32(3), 6);
assert_eq!(cpt.get32(4), 1); // default value
assert_eq!(cpt.get32(u32::MAX), 2); // error value

More Information

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