Yet another Bloom filter implementation for node.js. Everybody has to write one, as you know. Backed by FarmHash.
To install: npm install farmfilter
To create a filter, pass an options hash to the constructor:
const Filter = require('farmfilter');
const options =
{
bits: 1024,
hashes: 7,
seeds: [1, 2, 3, 4, 5, 6, 7]
};
const filter = new BloomFilter(options);
You can pass in seeds for the hash functions if you like, or they'll be randomly generated. Seeds must be integers.
You may also pass in a buffer as generated by filter.toBuffer()
.
To create a filter optimized for the number of items you'll be storing and a desired error rate:
filter = Filter.createOptimal(estimatedItemCount, errorRate);
The error rate parameter is optional. It defaults to 0.005, or a 0.5% rate. This is probably the constructor you want to use.
filter.add('cat');
Adds the given item to the filter. Can also accept buffers and arrays containing strings or buffers:
filter.add(['cat', 'dog', 'coati', 'red panda']);
To test for membership:
filter.has('dog');
To clear the filter:
filter.clear();
Returns a buffer with seeds and filter data.
Reconstitutes a filter from a freeze-dried buffer.
ISC.