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Add a nTweak to bloom filters to tweak the seed.

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This commit is contained in:
Matt Corallo
2012-11-02 18:33:50 -04:00
parent 4c8fc1a588
commit b1f99bed6f
3 changed files with 57 additions and 24 deletions
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6
src/bloom.h
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@@ -33,6 +33,7 @@ class CBloomFilter
private:
std::vector<unsigned char> vData;
unsigned int nHashFuncs;
unsigned int nTweak;
unsigned int Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const;
@@ -41,7 +42,9 @@ public:
// Note that if the given parameters will result in a filter outside the bounds of the protocol limits,
// the filter created will be as close to the given parameters as possible within the protocol limits.
// This will apply if nFPRate is very low or nElements is unreasonably high.
CBloomFilter(unsigned int nElements, double nFPRate);
// nTweak is a constant which is added to the seed value passed to the hash function
// It should generally always be a random value (and is largely only exposed for unit testing)
CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweak);
// Using a filter initialized with this results in undefined behavior
// Should only be used for deserialization
CBloomFilter() {}
@@ -50,6 +53,7 @@ public:
(
READWRITE(vData);
READWRITE(nHashFuncs);
READWRITE(nTweak);
)
void insert(const std::vector<unsigned char>& vKey);