Bloom Filter

This is an updated version of Brian Madden's rust-bloom-filter to compile for Rust 1.0+.

Bloom filter library implemented in Rust -- includes MurmurHash3 implementation, and simple bit vector library.

Only builds with nightly!

Still early implementation. Currently includes: working bloom filter library, working 32-bit murmurhash3 implementation, as well as a working bit vector library that can set, unset, flip bits.

Building

Libraries were built and tested using the master branch of Rust pulled on Feb 18, 2014. Libraries can be built using the included Makefile.

Use

bloom

The bloom crate exports one module, bloom_filter. The bloom_filter module exports a single object, BloomFilter with three public methods, new, insert, and maybe_present. The new method is static and can be used to create a new BloomFilter with specified expected number of insertions, and desired false positive rate. Example:

// Create new BloomFilter with 1000 expected elements, and false positive rate of 3%
let mut bf = BloomFilter::new(1000, 0.03);

insert will insert a string value into the bloom filter, and maybe_present will return true if queried value might be present, or false if it is definitely not present.

murmur3

The murmur library exports two public functions, murmur3_32_seeded and murmur3_32. The murmur3_32 function is simply a convenience function that calls murmur3_32_seeded with a seed value of 0. Both functions take a &str to be hashed and return a u32 value.

bit_vec

The bit_vec library contains a struct, Bit_vec that stores an vector of u8 bytes, and the desired size of the bit vector as an uint. Bounds checking is provided by checking against the size value.

A Bit_vec can be created with the constructor function new with a single uint size parameter. let my_bv: Bit_vec = Bit_vec::new(24);

The struct has four public methods available, set, unset, flip, and is_set. set will set a bit at the specified index position to 1, unset will set a bit at the specified index position to 0. flip will invert a bit at the specified index position, e.g. a 0 becomes a 1 and a 1 becomes a 0. is_set will return true if the bit at the specified index position is a 1, and false otherwise.

Examples

extern mod bloom_filter;

use bloom_filter::BloomFilter;

fn main() {

   let mut bv = BloomFilter::new("example", 0.03);
   bv.set("example");
   test_for_5(&bv);
   bv.unset(5);
   test_for_5(&bv);

}

fn test_for_5(bv: &BloomFilter) {
   if bv.is_set("example") == true { println!("Hooray!"); } else { println!("Boo!"); }
}

Should result in the following output:

Hooray!
Boo!

jonalmeida / bloom-filter