Note: This is a fork of github.com/willf/bloom that provides a read only bloom filter and a concurrent read only bloom filter that can both be instantiated from a mmap'd bytes ref and also limits the scope of the API.
A Bloom filter is a representation of a set of n items, where the main requirement is to make membership queries; i.e., whether an item is a member of a set.
A Bloom filter has two parameters: m, a maximum size (typically a reasonably large multiple of the cardinality of the set to represent) and k, the number of hashing functions on elements of the set. (The actual hashing functions are important, too, but this is not a parameter for this implementation). A Bloom filter is backed by a BitSet; a key is represented in the filter by setting the bits at each value of the hashing functions (modulo m). Set membership is done by testing whether the bits at each value of the hashing functions (again, modulo m) are set. If so, the item is in the set. If the item is actually in the set, a Bloom filter will never fail (the true positive rate is 1.0); but it is susceptible to false positives. The art is to choose k and m correctly.
In this implementation, the hashing functions used is murmurhash, a non-cryptographic hashing function.
This implementation accepts keys for setting and testing as []byte. Thus, to
add a string item, "Love":
n := uint(1000)
filter := bloom.NewBloomFilter(20*n, 5) // load of 20, 5 keys
filter.Add([]byte("Love"))
Similarly, to test if "Love" is in bloom:
if filter.Test([]byte("Love"))
Godoc documentation: https://godoc.org/github.com/m3db/bloom
go get -u github.com/m3db/bloomBefore committing the code, please check if it passes all tests using (note: this will install some dependencies):
make deps
make qa