Add a nTweak to bloom filters to tweak the seed.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/bloom.cpp b/src/bloom.cpp
index e773bbbbdb..65f9b021bf 100644
--- a/src/bloom.cpp
+++ b/src/bloom.cpp
@@ -15,7 +15,7 @@ using namespace std;
 
 static const unsigned char bit_mask[8] = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80};
 
-CBloomFilter::CBloomFilter(unsigned int nElements, double nFPRate) :
+CBloomFilter::CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweakIn) :
 // The ideal size for a bloom filter with a given number of elements and false positive rate is:
 // - nElements * log(fp rate) / ln(2)^2
 // We ignore filter parameters which will create a bloom filter larger than the protocol limits
@@ -23,14 +23,15 @@ vData(min((unsigned int)(-1  / LN2SQUARED * nElements * log(nFPRate)), MAX_BLOOM
 // The ideal number of hash functions is filter size * ln(2) / number of elements
 // Again, we ignore filter parameters which will create a bloom filter with more hash functions than the protocol limits
 // See http://en.wikipedia.org/wiki/Bloom_filter for an explanation of these formulas
-nHashFuncs(min((unsigned int)(vData.size() * 8 / nElements * LN2), MAX_HASH_FUNCS))
+nHashFuncs(min((unsigned int)(vData.size() * 8 / nElements * LN2), MAX_HASH_FUNCS)),
+nTweak(nTweakIn)
 {
 }
 
 inline unsigned int CBloomFilter::Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const
 {
     // 0xFBA4C795 chosen as it guarantees a reasonable bit difference between nHashNum values.
-    return MurmurHash3(nHashNum * 0xFBA4C795, vDataToHash) % (vData.size() * 8);
+    return MurmurHash3(nHashNum * 0xFBA4C795 + nTweak, vDataToHash) % (vData.size() * 8);
 }
 
 void CBloomFilter::insert(const vector<unsigned char>& vKey)