import xxhash from "xxhash-wasm";
const { h32 } = await xxhash();
/**
* BloomFilter Class
* Represents a BloomFilter Object
*/
class BloomFilter {
/**
* BloomFilter Constructor
* @param {number} [size=512] - Number of elements in the Bloom Filter, default 512
* @param {number} [size=3] - Number of rounds of hashing, default 3
*/
constructor(size = 512, hash = 3) {
if (size <= 1) throw new Error("Size should be bigger than 1");
if (hash < 1) throw new Error("Hash should be bigger than 1");
this.size = size;
this.hash = hash;
// Create ArrayBuffer
this.view = new DataView(new ArrayBuffer(this.size));
}
/**
* Add a new element to the Bloom Filter
* @param {string} input - Element to add - If array is provided all the elements will be added
*/
add(input) {
if (!Array.isArray(input)) input = [input];
for (let value of input) {
for (let i = 0; i < this.hash; i++) {
value = h32(value);
this.view.setInt8(parseInt(value, 16) % this.size, 1);
}
}
}
/**
* Returns if element may be present in the Bloom Filter
* @param {string} input - Element to check - If array is provided all the elements will be checked
* @returns {boolean} - True - If element may be present, False if element is definitely not present, if array was provided an boolean array will be returned
*/
has(input) {
if (!Array.isArray(input)) {
let value = input;
for (let i = 0; i < this.hash; i++) {
value = h32(value);
if (!this.view.getInt8(parseInt(value, 16) % this.size)) return false;
}
return true;
} else {
const output = [];
for (let value of input) output.push(this.has(value));
return output;
}
}
}
export { BloomFilter };