JS and WASM implementations of https://github.com/srijs/rust-gearhash

Using AssemblyScript to generate a lean WASM.

Usage

import { nextMatch } from '@huggingface/gearhash-wasm';

// Create a Uint8Array of data to search through
const data = new Uint8Array(1000000); // Example: 1MB of data
// ... fill data with your content ...

const mask = 0x0000d90003530000n; // Example mask as a BigInt, more 1s in binary repr => bigger chunks
//^ it has 11 1s in binary, so chunks will be ~2048 long
const match = nextMatch(data, mask);
const allMatches = nextMatches(data, mask).matches;

The nextMatch function takes two parameters:

• data: A Uint8Array containing the data to search through
• mask: A BigInt, the more 1s it has in its binary representation, the bigger the chunk

The function returns an object with the position (i32) and hash (u64) properties

You can continuously feed data like this:

let hash = 0n;
const mask = 0x0000d90003530000n;

let length = 0; // extra length not processed
for await (const chunk of dataSource) {
  let index = 0;
  while (1) {
    let match = nextMatch(chunk.subArray(index), mask, hash);

    if (match.position !== -1) {
      console.log({
        length: match.position + length,
        hash: match.hash
      })

      index += match.position;
      length = 0;
      hash = 0n;
    } else {
      length += chunk.length - index;
      break;
    }
  }
}

console.log(length, "bytes without a match, ending hash: ", hash);

or, more performant with nextMatches:

let hash = 0n;
const mask = 0x0000d90003530000n;

let length = 0;
for await (const chunk of dataSource) {
  const result = nextMatches(chunk, mask, hash);
  let lastPosition = 0;
  for (const match of result.matches) {
    console.log({
      length: match.position - lastPosition + length,
      hash: match.hash
    });

    length = 0;
    lastPosition = match.position;
  }
  length = result.remaining;
  hash = result.hash;
}

console.log(length, "bytes without a match, ending hash: ", hash);

Possible improvements

SIMD