mdietrichstein / objc-murmur3-bloomfilter

Bloom filter implementation using murmur3 hashing written in Objective-C

Objective-C Bloom Filter implementation

An Objective-C Bloom Filter implementation using 128 Bit (x64) Murmur3 Hashing. Hashes are generated using the Double Hashing Methond described in Less Hashing, Same Performance: Building a Better Bloom Filter.

Usage

NSUInteger expectedNumberOfItems = 10000;
double falsePositiveRate = 0.01;
uint32_t seed = 1234;
    
BloomFilter *bloomFilter = [[BloomFilter alloc] initWithExceptedNumberOfItems:expectedNumberOfItems falsePositiveRate:falsePositiveRate seed:seed];

// Containment
NSString *containedId = [[NSUUID UUID] UUIDString];
NSData *containedData = [containedId dataUsingEncoding:NSUTF8StringEncoding];
 
[bloomFilter add:containedData];
NSAssert([bloomFilter contains:containedData] == YES);

NSString *invalidId = [[NSUUID UUID] UUIDString];
NSData *invalidData = [containedId dataUsingEncoding:NSUTF8StringEncoding];
NSAssert([bloomFilter contains:invalidData] == NO);

// Serialization

BloomFilter *deserializedBloomFilter = [[BloomFilter alloc] initWithData:bloomFilter.data exceptedNumberOfItems:expectedNumberOfItems falsePositivePercentage:falsePositiveRate seed:seed];

NSAssert([deserializedBloomFilter contains:containedData] == YES);
NSAssert([deserializedBloomFilter contains:invalidData] == NO);

Resources

• Bloom Filter (Wikipedia)
• Murmur3 hash implementation (C++)
• Less Hashing, Same Performance: Building a Better Bloom Filter (pdf)