/**
* Core impl.
*
* @param n The expected #of index entries (this value is ignored for {@link IndexSegment}s).
* @param p The desired error rate for the bloom filter at that #of index entries (or at the
* actual #of index entries for an {@link IndexSegment}).
* @param maxP The maximum error rate for the bloom filter for a {@link BTree} (it will be
* disabled for a {@link BTree} once the bloom filter can be expected to realize this error
* rate).
* @throws IllegalArgumentException if <i>n</i> is non-positive.
* @throws IllegalArgumentException unless <i>p</i> lies in (0:1].
* @throws IllegalArgumentException
* @throws IllegalArgumentException unless <i>maxP</i> lies in (<i>p</i>:1].
*/
public BloomFilterFactory(final int n, final double p, final double maxP) {
if (n <= 0) throw new IllegalArgumentException();
if (p <= 0d || p > 1d) throw new IllegalArgumentException();
if (maxP <= p || maxP > 1d) throw new IllegalArgumentException();
this.n = n;
this.p = p;
this.maxP = maxP;
// #of hash functions.
final int k = BloomFilter.getHashFunctionCount(p);
// bit length of the filter.
final long m = BloomFilter.getBitLength(k, n);
/*
* The maximum #of index entries before we disable the filter because
* the expected performance will be worse than the specified maximum
* error rate.
*/
this.maxN = BloomFilter.getEntryCountForErrorRate(k, m, maxP);
}
