/home/palakars/workspace-inprogress/code-in-progress/aitools3/aitools3-aq-invertedindex-cpp/src/util/Checksum.cpp

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#include "Checksum.hpp"
#include <iostream>
#include <cmath>

namespace aitools{
namespace invertedindex {

bool
Checksum::is_prime(uint32_t number)
{
        if (number == 2) return true;
        if (number < 2 || number % 2 == 0) return false;
        for (unsigned i(3); i <= std::sqrt(number); ++++i)
        {
                if (number % i == 0) return false;
        }
        return true;
}

uint32_t
Checksum::next_prime(uint32_t number)
{
        while (!is_prime(number)) ++number;
        return number;
}

uint16_t
Checksum::hash16(const std::string& key)
{
        return hash32(key) % uint16_max;
}

uint32_t
Checksum::hash32(const std::string& key)
{
        return hash32(key.data(), key.length());
}

uint32_t
Checksum::hash32(const char* key, size_t length)
{
        // Included from ../tr1_impl/functional_hash.h
        uint32_t result(static_cast<uint32_t>(2166136261UL));
        for (; length > 0; --length)
        {
                result ^= static_cast<uint32_t>(*key++);
                result *= static_cast<uint32_t>(16777619UL);
        }
        return result;
}

} // namespace invertedindex
} // namespace aitools

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