tab-hash - Tabulation Hashing for Rust

This crate offers Rust implementations of simple, twisted, and mixed tabulation hashing for 32-bit and 64-bit integer values.

Instantiating Tab32Simple, Tab32Twisted, or Tab32Mixed (or their 64-bit counterparts) will initialize tables and create a random hash function from the respective hash family. The hash value of an integer key is computed by calling its hash method.

Simple tabulation example

use tab_hash::Tab32Simple;

fn main() {
    let keys = vec![0, 8, 15, 47, 11];
    let simple = Tab32Simple::new();
    for k in keys {
        println!("{}", simple.hash(k));
    }
}

Mixed tabulation example

Tab32Mixed and Tab64Mixed use the same new and hash interface as the simple and twisted variants:

use tab_hash::{Tab32Mixed, Tab64Mixed};

fn main() {
    let mixed32 = Tab32Mixed::new();
    let mixed64 = Tab64Mixed::new();

    println!("32-bit hash: {}", mixed32.hash(42_u32));
    println!("64-bit hash: {}", mixed64.hash(42_u64));
}

To reproduce hashes, save the table used by the hash function. The function can be recreated using the with_table constructor.

use tab_hash::Tab64Twisted;

fn main() {
    let key = 42;
    let twisted_1 = Tab64Twisted::new();
    let twisted_2 = Tab64Twisted::with_table(twisted_1.get_table());
    let twisted_3 = Tab64Twisted::new();
    assert_eq!(twisted_1.hash(key), twisted_2.hash(key));
    assert_ne!(twisted_1.hash(key), twisted_3.hash(key));
}

Mixed tabulation has two tables. Pass both values returned by get_table to with_table to recreate the same hash function:

use tab_hash::Tab64Mixed;

fn main() {
    let key = 42;
    let mixed_1 = Tab64Mixed::new();
    let (first_table, second_table) = mixed_1.get_table();
    let mixed_2 = Tab64Mixed::with_table(first_table, second_table);

    assert_eq!(mixed_1.hash(key), mixed_2.hash(key));
}

Note:

These hash functions do not implement the std::hash::Hasher trait, since they do not work on arbitrary length byte streams.

The 64-bit version of twisted tabulation hashing (Tab64Twisted) requires 128-bit operations (see here).

Mixed tabulation first derives additional 8-bit characters and then hashes the original and derived characters together. In the notation from the mixed tabulation papers, c is the number of input characters and d is the number of derived characters. The theory allows any fixed d >= 1; larger d reduces the failure-probability terms in the analysis, at the cost of d extra table lookups and d extra tables. This crate follows the common implementation choice d = c: Tab32Mixed performs 4 + 4 table lookups, while Tab64Mixed performs 8 + 8 table lookups.

Literature:

This implementation is based on the articles of Mihai Pătraşcu, Mikkel Thorup, Søren Dahlgaard, et al.:

Changelog

Version 0.4.0 [2026-08-03]

Add mixed tabulation hashing. Thanks @jianshu93
Updated edition
Updated dependencies

Version 0.3.0 [2020-02-12]

Made all structs serializable and deserializable.

tab-hash 0.4.0