@platformatic/kafka/dist/protocol/murmur2.js

Modern and performant client for Apache Kafka

import { LRUCache } from 'mnemonist';
// This is a Javascript port of
// https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/common/utils/Utils.java#L492
// 'm' and 'r' are mixing constants generated offline. They're not really 'magic', they just happen to work well.
const seed = 0x9747b28cn;
const m = 0x5bd1e995n;
const r = 24;
const cache = new LRUCache(1000);
const tail = Buffer.alloc(4);
function tripleRightShift(num, bits) {
    return BigInt(Number(BigInt.asIntN(32, num)) >>> bits);
}
export function murmur2(data, useCache = false) {
    let key;
    if (typeof data === 'string') {
        if (useCache) {
            key = data;
            const existing = key ? cache.get(key) : undefined;
            if (existing) {
                return existing;
            }
        }
        data = Buffer.from(data);
    }
    const length = data.length;
    // Initialize the hash to a random value
    let h = seed ^ BigInt(length);
    let i = 0;
    while (i < length - 3) {
        let k = BigInt(data.readInt32LE(i));
        i += 4;
        k *= m;
        k ^= tripleRightShift(k, r);
        k *= m;
        h *= m;
        h ^= k;
    }
    // Read the last few bytes of the input array
    // If this becomes an hot-path, consider to optimize it further and avoid copying
    if (length % 4 > 0) {
        data.copy(tail, 0, length - (length % 4));
        h ^= BigInt(tail.readInt32LE(0));
        tail.fill(0);
        h *= m;
    }
    // Perform the final mixing
    h ^= tripleRightShift(h, 13);
    h *= m;
    h ^= tripleRightShift(h, 15);
    const hash = Number(BigInt.asIntN(32, h));
    if (key !== undefined) {
        cache.set(key, hash);
    }
    return hash;
}