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Performance optimization for bloom filters.

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This reduces a peer's ability to attack network resources by
 using a full bloom filter, but without reducing the usability
 of bloom filters.  It sets a default match everything filter
 for peers and it generalizes a prior optimization to
 cover more cases.
This commit is contained in:
Gregory Maxwell
2013-08-18 20:21:06 -07:00
parent 4bc9a19269
commit 37c6389c5a
4 changed files with 33 additions and 7 deletions
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26
src/bloom.cpp
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@@ -23,6 +23,8 @@ 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
isFull(false),
isEmpty(false),
nHashFuncs(min((unsigned int)(vData.size() * 8 / nElements * LN2), MAX_HASH_FUNCS)),
nTweak(nTweakIn),
nFlags(nFlagsIn)
@@ -37,7 +39,7 @@ inline unsigned int CBloomFilter::Hash(unsigned int nHashNum, const std::vector<
void CBloomFilter::insert(const vector<unsigned char>& vKey)
{
if (vData.size() == 1 && vData[0] == 0xff)
if (isFull)
return;
for (unsigned int i = 0; i < nHashFuncs; i++)
{
@@ -45,6 +47,7 @@ void CBloomFilter::insert(const vector<unsigned char>& vKey)
// Sets bit nIndex of vData
vData[nIndex >> 3] |= bit_mask[7 & nIndex];
}
isEmpty = false;
}
void CBloomFilter::insert(const COutPoint& outpoint)
@@ -63,8 +66,10 @@ void CBloomFilter::insert(const uint256& hash)
bool CBloomFilter::contains(const vector<unsigned char>& vKey) const
{
if (vData.size() == 1 && vData[0] == 0xff)
if (isFull)
return true;
if (isEmpty)
return false;
for (unsigned int i = 0; i < nHashFuncs; i++)
{
unsigned int nIndex = Hash(i, vKey);
@@ -99,6 +104,10 @@ bool CBloomFilter::IsRelevantAndUpdate(const CTransaction& tx, const uint256& ha
bool fFound = false;
// Match if the filter contains the hash of tx
// for finding tx when they appear in a block
if (isFull)
return true;
if (isEmpty)
return false;
if (contains(hash))
fFound = true;
@@ -158,3 +167,16 @@ bool CBloomFilter::IsRelevantAndUpdate(const CTransaction& tx, const uint256& ha
return false;
}
void CBloomFilter::UpdateEmptyFull()
{
bool full = true;
bool empty = true;
for (unsigned int i = 0; i < vData.size(); i++)
{
full &= vData[i] == 0xff;
empty &= vData[i] == 0;
}
isFull = full;
isEmpty = empty;
}