A modified version of Fletcher & Adler checksums plus an optional iterative hash function, by Lucy Havok.
Fletcher's Checksum algorithm is way overengineered. Adler had the right idea with many of the tweaks he made to simplify and solidify the algorithm. However, I liked the idea of having a user-defined arbitrary checksum bitdepth, but also make sure that the modulo is always prime so as to reduce checksum collision.
| Fletcher | Adler | Havok | |
|---|---|---|---|
| Word Size | 8b | 16b | 32b | 8b | 8b |
| Bits | 16 | 32 | 64 | 32 | arbitrary |
| Modulo | 28 | 216 | 232 | 65,521 | nearest prime under 2Bits |
| Shift | 8 | 16 | 32 | 16 | Bits/2 |
| Iterative Hash | no | no | optional, arbitrary |
composer require luhav/havok-nuse Luhav\HavokN;
$havokN = new HavokN();
$data = "Toast"; // This is the data you want a sum of. Can be of any type.
$bitdepth = 16; // This is sort of like the length of the checksum, but it's not directly proportionate. If you wanted to pretend this is Adler-32, you would put 32 here. Should be an integer.
$iterations = 0; // Optional. This is the number of iterations over the iterative hash function (defaults to 0).
$havokN->sum($data, $bitdepth, $iterations);Havok-N is part of the EmojiHash project at Peepee Party, of which I am the creator, maintainer, and current sole contributor. The upstream version of havokn.php can be seen at https://fossil.peepee.party/emojihash/file?name=php/havokn.php.
Havok-N is licensed under The 3-Clause BSD License with the explicit military disclaimer (SPDX: BSD-3-Clause-No-Military-License). See LICENSE for the full text.