bloom: use Span instead of std::vector for insert and contains

We can avoid many unnecessary std::vector allocations by changing
CBloomFilter to take Spans instead of std::vector's for the `insert`
and `contains` operations.

CBloomFilter currently converts types such as CDataStream and uint256
to std::vector on `insert` and `contains`. This is unnecessary because
CDataStreams and uint256 are already std::vectors internally. We just
need a way to point to the right data within those types. Span gives
us this ability.

Signed-off-by: William Casarin <jb55@jb55.com>

src/bloom.cpp

@@ -37,13 +37,13 @@ CBloomFilter::CBloomFilter(const unsigned int nElements, const double nFPRate, c
 {
 }
 
-inline unsigned int CBloomFilter::Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const
+inline unsigned int CBloomFilter::Hash(unsigned int nHashNum, Span<const unsigned char> vDataToHash) const
 {
     // 0xFBA4C795 chosen as it guarantees a reasonable bit difference between nHashNum values.
     return MurmurHash3(nHashNum * 0xFBA4C795 + nTweak, vDataToHash) % (vData.size() * 8);
 }
 
-void CBloomFilter::insert(const std::vector<unsigned char>& vKey)
+void CBloomFilter::insert(Span<const unsigned char> vKey)
 {
     if (vData.empty()) // Avoid divide-by-zero (CVE-2013-5700)
         return;
@@ -59,17 +59,10 @@ void CBloomFilter::insert(const COutPoint& outpoint)
 {
     CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
     stream << outpoint;
-    std::vector<unsigned char> data(stream.begin(), stream.end());
-    insert(data);
+    insert(stream);
 }
 
-void CBloomFilter::insert(const uint256& hash)
-{
-    std::vector<unsigned char> data(hash.begin(), hash.end());
-    insert(data);
-}
-
-bool CBloomFilter::contains(const std::vector<unsigned char>& vKey) const
+bool CBloomFilter::contains(Span<const unsigned char> vKey) const
 {
     if (vData.empty()) // Avoid divide-by-zero (CVE-2013-5700)
         return true;
@@ -87,14 +80,7 @@ bool CBloomFilter::contains(const COutPoint& outpoint) const
 {
     CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
     stream << outpoint;
-    std::vector<unsigned char> data(stream.begin(), stream.end());
-    return contains(data);
-}
-
-bool CBloomFilter::contains(const uint256& hash) const
-{
-    std::vector<unsigned char> data(hash.begin(), hash.end());
-    return contains(data);
+    return contains(MakeUCharSpan(stream));
 }
 
 bool CBloomFilter::IsWithinSizeConstraints() const
@@ -198,7 +184,8 @@ CRollingBloomFilter::CRollingBloomFilter(const unsigned int nElements, const dou
 }
 
 /* Similar to CBloomFilter::Hash */
-static inline uint32_t RollingBloomHash(unsigned int nHashNum, uint32_t nTweak, const std::vector<unsigned char>& vDataToHash) {
+static inline uint32_t RollingBloomHash(unsigned int nHashNum, uint32_t nTweak, Span<const unsigned char> vDataToHash)
+{
     return MurmurHash3(nHashNum * 0xFBA4C795 + nTweak, vDataToHash);
 }
 
@@ -210,7 +197,7 @@ static inline uint32_t FastMod(uint32_t x, size_t n) {
     return ((uint64_t)x * (uint64_t)n) >> 32;
 }
 
-void CRollingBloomFilter::insert(const std::vector<unsigned char>& vKey)
+void CRollingBloomFilter::insert(Span<const unsigned char> vKey)
 {
     if (nEntriesThisGeneration == nEntriesPerGeneration) {
         nEntriesThisGeneration = 0;
@@ -241,13 +228,7 @@ void CRollingBloomFilter::insert(const std::vector<unsigned char>& vKey)
     }
 }
 
-void CRollingBloomFilter::insert(const uint256& hash)
-{
-    std::vector<unsigned char> vData(hash.begin(), hash.end());
-    insert(vData);
-}
-
-bool CRollingBloomFilter::contains(const std::vector<unsigned char>& vKey) const
+bool CRollingBloomFilter::contains(Span<const unsigned char> vKey) const
 {
     for (int n = 0; n < nHashFuncs; n++) {
         uint32_t h = RollingBloomHash(n, nTweak, vKey);
@@ -261,12 +242,6 @@ bool CRollingBloomFilter::contains(const std::vector<unsigned char>& vKey) const
     return true;
 }
 
-bool CRollingBloomFilter::contains(const uint256& hash) const
-{
-    std::vector<unsigned char> vData(hash.begin(), hash.end());
-    return contains(vData);
-}
-
 void CRollingBloomFilter::reset()
 {
     nTweak = GetRand(std::numeric_limits<unsigned int>::max());

src/bloom.h

@@ -11,7 +11,6 @@
 
 class COutPoint;
 class CTransaction;
-class uint256;
 
 //! 20,000 items with fp rate < 0.1% or 10,000 items and <0.0001%
 static const unsigned int MAX_BLOOM_FILTER_SIZE = 36000; // bytes
@@ -49,7 +48,7 @@ private:
     unsigned int nTweak;
     unsigned char nFlags;
 
-    unsigned int Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const;
+    unsigned int Hash(unsigned int nHashNum, Span<const unsigned char> vDataToHash) const;
 
 public:
     /**
@@ -66,13 +65,11 @@ public:
 
     SERIALIZE_METHODS(CBloomFilter, obj) { READWRITE(obj.vData, obj.nHashFuncs, obj.nTweak, obj.nFlags); }
 
-    void insert(const std::vector<unsigned char>& vKey);
+    void insert(Span<const unsigned char> vKey);
     void insert(const COutPoint& outpoint);
-    void insert(const uint256& hash);
 
-    bool contains(const std::vector<unsigned char>& vKey) const;
+    bool contains(Span<const unsigned char> vKey) const;
     bool contains(const COutPoint& outpoint) const;
-    bool contains(const uint256& hash) const;
 
     //! True if the size is <= MAX_BLOOM_FILTER_SIZE and the number of hash functions is <= MAX_HASH_FUNCS
     //! (catch a filter which was just deserialized which was too big)
@@ -112,10 +109,8 @@ class CRollingBloomFilter
 public:
     CRollingBloomFilter(const unsigned int nElements, const double nFPRate);
 
-    void insert(const std::vector<unsigned char>& vKey);
-    void insert(const uint256& hash);
-    bool contains(const std::vector<unsigned char>& vKey) const;
-    bool contains(const uint256& hash) const;
+    void insert(Span<const unsigned char> vKey);
+    bool contains(Span<const unsigned char> vKey) const;
 
     void reset();
 

src/hash.cpp

@@ -3,6 +3,7 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <hash.h>
+#include <span.h>
 #include <crypto/common.h>
 #include <crypto/hmac_sha512.h>
 

src/test/bloom_tests.cpp

@@ -83,7 +83,7 @@ BOOST_AUTO_TEST_CASE(bloom_create_insert_key)
     CBloomFilter filter(2, 0.001, 0, BLOOM_UPDATE_ALL);
     filter.insert(vchPubKey);
     uint160 hash = pubkey.GetID();
-    filter.insert(std::vector<unsigned char>(hash.begin(), hash.end()));
+    filter.insert(hash);
 
     CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
     stream << filter;