Crate trie_rs

trie-rs

Memory efficient trie (prefix tree) and map library based on LOUDS.

Master API Docs | Released API Docs | Benchmark Results | Changelog

Quickstart

To use trie-rs, add the following to your Cargo.toml file:

[dependencies]
trie-rs = "0.4.2"

Usage Overview

use std::str;
use trie_rs::TrieBuilder;

let mut builder = TrieBuilder::new();  // Inferred `TrieBuilder<u8>` automatically
builder.push("すし");
builder.push("すしや");
builder.push("すしだね");
builder.push("すしづめ");
builder.push("すしめし");
builder.push("すしをにぎる");
builder.push("すし");  // Word `push`ed twice is just ignored.
builder.push("🍣");

let trie = builder.build();

// exact_match(): Find a word exactly match to query.
assert_eq!(trie.exact_match("すし"), true);
assert_eq!(trie.exact_match("🍣"), true);
assert_eq!(trie.exact_match("🍜"), false);

// predictive_search(): Find words which include `query` as their prefix.
let results_in_u8s: Vec<Vec<u8>> = trie.predictive_search("すし").collect();
let results_in_str: Vec<String> = trie.predictive_search("すし").collect();
assert_eq!(
    results_in_str,
    vec![
        "すし",
        "すしだね",
        "すしづめ",
        "すしめし",
        "すしや",
        "すしをにぎる"
    ]  // Sorted by `Vec<u8>`'s order
);

// common_prefix_search(): Find words which is included in `query`'s prefix.
let results_in_u8s: Vec<Vec<u8>> = trie.common_prefix_search("すしや").collect();
let results_in_str: Vec<String> = trie.common_prefix_search("すしや").collect();
assert_eq!(
    results_in_str,
    vec![
        "すし",
        "すしや",
    ]  // Sorted by `Vec<u8>`'s order
);

Using with Various Data Types

TrieBuilder is implemented using generic type like following:

impl<Label: Ord> TrieBuilder<Label> {
    ...
    pub fn push<Arr: AsRef<[Label]>>(&mut self, word: Arr) where Label: Clone { ... }
    ...
}

In the above Usage Overview example, we used Label=u8, Arr=&str. If Label does not implement Clone, use insert().

Here shows other Label and Arr type examples.

Label=&str, Arr=Vec<&str>

Say Label is English words and Arr is English phrases.

use trie_rs::TrieBuilder;

let mut builder = TrieBuilder::new();
builder.push(vec!["a", "woman"]);
builder.push(vec!["a", "woman", "on", "the", "beach"]);
builder.push(vec!["a", "woman", "on", "the", "run"]);

let trie = builder.build();

assert_eq!(
    trie.exact_match(vec!["a", "woman", "on", "the", "beach"]),
    true
);
let r: Vec<Vec<&str>> = trie.predictive_search(vec!["a", "woman", "on"]).collect();
assert_eq!(
    r,
    vec![
        ["a", "woman", "on", "the", "beach"],
        ["a", "woman", "on", "the", "run"],
    ],
);
let s: Vec<Vec<&str>> = trie.common_prefix_search(vec!["a", "woman", "on", "the", "beach"]).collect();
assert_eq!(
    s,
    vec![vec!["a", "woman"], vec!["a", "woman", "on", "the", "beach"]],
);

Label=u8, Arr=[u8; n]

Say Label is a digit in Pi (= 3.14…) and Arr is a window to separate pi’s digit by 10.

use trie_rs::TrieBuilder;

let mut builder = TrieBuilder::<u8>::new(); // Pi = 3.14...

builder.push([1, 4, 1, 5, 9, 2, 6, 5, 3, 5]);
builder.push([8, 9, 7, 9, 3, 2, 3, 8, 4, 6]);
builder.push([2, 6, 4, 3, 3, 8, 3, 2, 7, 9]);
builder.push([6, 9, 3, 9, 9, 3, 7, 5, 1, 0]);
builder.push([5, 8, 2, 0, 9, 7, 4, 9, 4, 4]);
builder.push([5, 9, 2, 3, 0, 7, 8, 1, 6, 4]);
builder.push([0, 6, 2, 8, 6, 2, 0, 8, 9, 9]);
builder.push([8, 6, 2, 8, 0, 3, 4, 8, 2, 5]);
builder.push([3, 4, 2, 1, 1, 7, 0, 6, 7, 9]);
builder.push([8, 2, 1, 4, 8, 0, 8, 6, 5, 1]);
builder.push([3, 2, 8, 2, 3, 0, 6, 6, 4, 7]);
builder.push([0, 9, 3, 8, 4, 4, 6, 0, 9, 5]);
builder.push([5, 0, 5, 8, 2, 2, 3, 1, 7, 2]);
builder.push([5, 3, 5, 9, 4, 0, 8, 1, 2, 8]);

let trie = builder.build();

assert_eq!(trie.exact_match([5, 3, 5, 9, 4, 0, 8, 1, 2, 8]), true);

let t: Vec<Vec<u8>> = trie.predictive_search([3]).collect();
assert_eq!(
    t,
    vec![
        [3, 2, 8, 2, 3, 0, 6, 6, 4, 7],
        [3, 4, 2, 1, 1, 7, 0, 6, 7, 9],
    ],
);
let u: Vec<Vec<u8>> = trie.common_prefix_search([1, 4, 1, 5, 9, 2, 6, 5, 3, 5]).collect();
assert_eq!(
    u,
    vec![[1, 4, 1, 5, 9, 2, 6, 5, 3, 5]],
);

Trie Map Usage

To store a value with each word, use trie_rs::map::{Trie, TrieBuilder}.

use std::str;
use trie_rs::map::TrieBuilder;

let mut builder = TrieBuilder::new();  // Inferred `TrieBuilder<u8, u8>` automatically
builder.push("すし", 0);
builder.push("すしや", 1);
builder.push("すしだね", 2);
builder.push("すしづめ", 3);
builder.push("すしめし", 4);
builder.push("すしをにぎる", 5);
builder.push("すし", 6);  // Word `push`ed twice uses last value.
builder.push("🍣", 7);

let mut trie = builder.build();

// exact_match(): Find a word exactly match to query.
assert_eq!(trie.exact_match("すし"), Some(&6));
assert_eq!(trie.exact_match("🍣"), Some(&7));
assert_eq!(trie.exact_match("🍜"), None);

// Values can be modified.
let v = trie.exact_match_mut("🍣").unwrap();
*v = 8;
assert_eq!(trie.exact_match("🍣"), Some(&8));

Incremental Search

For interactive applications, one can use an incremental search to get the best performance. See IncSearch.

use std::str;
use trie_rs::{TrieBuilder, inc_search::Answer};

let mut builder = TrieBuilder::new();  // Inferred `TrieBuilder<u8, u8>` automatically
builder.push("ab");
builder.push("すし");
builder.push("すしや");
builder.push("すしだね");
builder.push("すしづめ");
builder.push("すしめし");
builder.push("すしをにぎる");
let trie = builder.build();
let mut search = trie.inc_search();

// Query by the byte.
assert_eq!(search.query(&b'a'), Some(Answer::Prefix));
assert_eq!(search.query(&b'c'), None);
assert_eq!(search.query(&b'b'), Some(Answer::Match));

// Reset the query to go again.
search.reset();

// For unicode its easier to use .query_until().
assert_eq!(search.query_until("す"), Ok(Answer::Prefix));
assert_eq!(search.query_until("し"), Ok(Answer::PrefixAndMatch));
assert_eq!(search.query_until("や"), Ok(Answer::Match));
assert_eq!(search.query(&b'a'), None);
assert_eq!(search.query_until("a"), Err(0));

search.reset();
assert_eq!(search.query_until("ab-NO-MATCH-"), Err(2)); // No match on byte at index 2.

Features

• Generic type support: As the above examples show, trie-rs can be used for searching not only UTF-8 string but also other data types.
• Based on louds-rs, which is fast, parallelized, and memory efficient.
• Latest benchmark results are always accessible: trie-rs is continuously benchmarked in Travis CI using Criterion.rs. Graphical benchmark results are published here.
• map::Trie associates a Value with each entry.
• Value does not require any traits.
• Label: Clone not required to create Trie<Label> but useful for many reifying search operations like predictive_search().
• Many search operations are implemented via iterators which are lazy, require less memory, and can be short circuited.
• Incremental search available for “online” applications, i.e., searching one Label at a time.

Cargo features

• “rayon”

Enables rayon a data parallelism library.

• “mem_dbg”

Can determine the size in bytes of nested data structures like the trie itself.

• “serde”

Can serialize and deserialize the trie.

Acknowledgments

edict.furigana is used for benchmark. This file is constructed in the following step:

1. Download edict.gz from EDICT.
2. Convert it from original EUC into UTF-8.
3. Translate it into CSV file with edict-to-csv.
4. Extract field $1 for Hiragana/Katakana words, and field $3 for other (like Kanji) words.
5. Translate Katakana into Hiragana with kana2hira.

Many thanks for these dictionaries and tools.

Versions

trie-rs uses semantic versioning.

Since current major version is 0, minor version update might involve breaking public API change (although it is carefully avoided).

Rust Version Supports

trie-rs is continuously tested with these Rust versions in with the github CI:

• 1.75.0 with all features
• 1.67.0 with no features
• Latest stable version

So it is expected to work with Rust 1.75.0 and any newer versions.

Older versions may also work but are not tested or guaranteed.

Earlier Rust Verion Supports

If support for Rust prior to 1.67.0 is required, trie-rs 0.2.0 supports Rust 1.33.0 and later.

Contributing

Any kind of pull requests are appreciated.

License

MIT OR Apache-2.0

Modules

• inc_search
  Incremental search
• iter
  Trie iterators
• map
  A trie that maps sequence of Labels to a Value.
• try_collect
  Try to collect from an iterator; operation may fail.

Structs

• Trie
  A trie for sequences of the type Label.
• TrieBuilder
  A trie builder for Trie.