Class CascadingBloomFilter

src/rnabloom/bloom/CascadingBloomFilter.java:25–143

@author Ka Ming Nip

 * @author Ka Ming Nip
 */
public class CascadingBloomFilter implements BloomFilterInterface {
    protected final BloomFilter[] bfs;
    protected final BloomFilter topLevelBf;
    protected final int numLevels;
    protected final long size; // number of bits
    protected final long partitionSize;
    protected final int numHash;
    protected final HashFunction hashFunction;
    
    public CascadingBloomFilter(long size, int numHash, HashFunction hashFunction, int numLevels) {
        this.numLevels = numLevels;
        bfs = new BloomFilter[numLevels];
        this.size = size;
        this.partitionSize = size/numLevels;
        this.numHash = numHash;
        this.hashFunction = hashFunction;
        for (int i=0; i<numLevels; ++i) {
            bfs[i] = new BloomFilter(partitionSize, numHash, hashFunction);
        }
        topLevelBf = bfs[numLevels-1];
    }
    
    public int getNumLevels() {
        return numLevels;
    }
    
    public BloomFilter getBloomFilter(int level) {
        return bfs[level];
    }
    
    @Override
    public void add(String key) {
        long[] hashVals = new long[numHash];
        this.hashFunction.getHashValues(key, numHash, hashVals);
        add(hashVals);
    }

    public void add(long hashVal) {
        add(this.hashFunction.getHashValues(hashVal, numHash));
    }
    
    public void add(long[] hashVals) {
        for (BloomFilter bf : bfs) {
            if (!bf.lookupThenAdd(hashVals)) {
                break;
            }
        }
    }
    
    @Override
    public boolean lookup(String key) {
        long[] hashVals = new long[numHash];
        this.hashFunction.getHashValues(key, numHash, hashVals);
        return lookup(hashVals);
    }

    public boolean lookup(long hashVal) {
        return topLevelBf.lookup(hashVal);