bloom-filters/test/compatibility-test.js

JS implementation of probabilistic data structures: Bloom Filter (and its derived), HyperLogLog, Count-Min Sketch, Top-K and MinHash

/*
MIT License

Copyright (c) 2022 Arnaud Grall

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*/

require('chai').should()
const {expect} = require('chai')
const {BloomFilter, DeprecatedHashing} = require('../dist/api.js')

describe('BloomFilter Compatibility (only) between versions', () => {
  it('1.3.4 compatibility (issue #49)', () => {
    const bl = BloomFilter.create(15, 0.1)
    bl.seed = 1
    bl._hashing = new DeprecatedHashing()
    bl.add('alice')
    bl.add('bob')
    // compatibility with the current version
    expect(bl.saveAsJSON()).to.deep.equal({
      type: 'BloomFilter',
      _size: 72,
      _nbHashes: 4,
      _filter: {size: 72, content: 'AEkCAACCIAgA'},
      _seed: 1,
    })
    // these indexes are generated using the 1.3.4 version
    let indexes = bl._hashing.getDistinctIndexes(
      'alice',
      bl._size,
      bl._nbHashes,
      1
    )
    expect(indexes).to.deep.equal([59, 53, 47, 41])
    indexes = bl._hashing.getDistinctIndexes('bob', bl._size, bl._nbHashes, 1)
    expect(indexes).deep.equal([17, 14, 11, 8])

    // try to import an old 1.3.4 filter to the new format
    const filter = {
      type: 'BloomFilter',
      _seed: 1,
      _size: 72,
      _nbHashes: 4,
      _filter: [
        0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1,
        0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      ],
    }
    const importedBl = BloomFilter.fromJSON(filter)
    importedBl._hashing = new DeprecatedHashing() // dont forget this line or the .has() wont work correctly
    bl.equals(importedBl).should.be.true
    importedBl.has('alice').should.be.true
    importedBl.has('bob').should.be.true
  })
})