bloom_filter.cpp

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#include <cassert>           
#include <functional>        
#include <initializer_list>  
#include <string>            
#include <vector>            
#include <iostream>          
 
namespace data_structures {
class Bitset {
 private:
    std::vector<std::size_t> data;  
    static const std::size_t blockSize =
        sizeof(std::size_t);  
 public:
    explicit Bitset(std::size_t);
    std::size_t size();
    void add(std::size_t);
    bool contains(std::size_t);
};
 
std::size_t Bitset::size() { return data.size(); }
 
Bitset::Bitset(std::size_t initSize) : data(initSize) {}
 
void Bitset::add(std::size_t x) {
    std::size_t blockIndex = x / blockSize;
    if (blockIndex >= data.size()) {
        data.resize(blockIndex + 1);
    }
    data[blockIndex] |= 1 << (x % blockSize);
}
 
bool Bitset::contains(std::size_t x) {
    std::size_t blockIndex = x / blockSize;
    if (blockIndex >= data.size()) {
        return false;
    }
    return data[blockIndex] & (1 << (x % blockSize));
}
 
template <typename T>
class BloomFilter {
 private:
    Bitset set;  
    std::vector<std::function<std::size_t(T)>>
        hashFunks;  
 
 public:
    BloomFilter(std::size_t,
                std::initializer_list<std::function<std::size_t(T)>>);
    void add(T);
    bool contains(T);
};
 
template <typename T>
BloomFilter<T>::BloomFilter(
    std::size_t size,
    std::initializer_list<std::function<std::size_t(T)>> funks)
    : set(size), hashFunks(funks) {}
 
template <typename T>
void BloomFilter<T>::add(T x) {
    for (std::size_t i = 0; i < hashFunks.size(); i++) {
        set.add(hashFunks[i](x) % (sizeof(std::size_t) * set.size()));
    }
}
 
template <typename T>
bool BloomFilter<T>::contains(T x) {
    for (std::size_t i = 0; i < hashFunks.size(); i++) {
        if (set.contains(hashFunks[i](x) %
                         (sizeof(std::size_t) * set.size())) == false) {
            return false;
        }
    }
    return true;
}
 
static std::size_t hashDJB2(std::string const& s) {
    std::size_t hash = 5381;
    for (char c : s) {
        hash = ((hash << 5) + hash) + c;
    }
    return hash;
}
 
static std::size_t hashStr(std::string const& s) {
    std::size_t hash = 37;
    std::size_t primeNum1 = 54059;
    std::size_t primeNum2 = 76963;
    for (char c : s) {
        hash = (hash * primeNum1) ^ (c * primeNum2);
    }
    return hash;
}
 
std::size_t hashInt_1(int x) {
    x = ((x >> 16) ^ x) * 0x45d9f3b;
    x = ((x >> 16) ^ x) * 0x45d9f3b;
    x = (x >> 16) ^ x;
    return x;
}
 
std::size_t hashInt_2(int x) {
    auto y = static_cast<std::size_t>(x);
    y = (y ^ (y >> 30)) * static_cast<std::size_t>(0xbf58476d1ce4e5b9);
    y = (y ^ (y >> 27)) * static_cast<std::size_t>(0x94d049bb133111eb);
    y = y ^ (y >> 31);
    return y;
}
}  // namespace data_structures
 
static void test_bloom_filter_string() {
    data_structures::BloomFilter<std::string> filter(
        10, {data_structures::hashDJB2, data_structures::hashStr});
    std::vector<std::string> toCheck{"hello", "world", "!"};
    std::vector<std::string> toFalse{"false", "world2", "!!!"};
    for (const auto& x : toCheck) {
        filter.add(x);
    }
    for (const auto& x : toFalse) {
        assert(filter.contains(x) == false);
    }
    for (const auto& x : toCheck) {
        assert(filter.contains(x));
    }
}
 
static void test_bloom_filter_int() {
    data_structures::BloomFilter<int> filter(
        20, {data_structures::hashInt_1, data_structures::hashInt_2});
    std::vector<int> toCheck{100, 200, 300, 50};
    std::vector<int> toFalse{1, 2, 3, 4, 5, 6, 7, 8};
    for (int x : toCheck) {
        filter.add(x);
    }
    for (int x : toFalse) {
        assert(filter.contains(x) == false);
    }
    for (int x : toCheck) {
        assert(filter.contains(x));
    }
}
 
static void test_bitset() {
    data_structures::Bitset set(2);
    std::vector<std::size_t> toCheck{0, 1, 5, 8, 63, 64, 67, 127};
    for (auto x : toCheck) {
        set.add(x);
        assert(set.contains(x));
    }
    assert(set.contains(128) == false);
    assert(set.contains(256) == false);
}
 
int main() {
    // run self-test implementations
 
    test_bitset();  // run test for bitset, because bloom filter is depending on it
    test_bloom_filter_string();
    test_bloom_filter_int();
    
    std::cout << "All tests have successfully passed!\n";
    return 0;
}