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#pragma once
#include <cstdlib>
#include <memory>
#include "Vector3.h"
#include "SHA256.h"
namespace math
{
namespace detail
{
// Delivers 10.0^significantDigits
constexpr double RoundingFactor(std::size_t significantDigits)
{
return significantDigits == 1 ? 10.0 : 10.0 * RoundingFactor(significantDigits - 1);
}
}
// A hash combination function based on the one used in boost and found on stackoverflow
inline void combineHash(std::size_t& seed, std::size_t hash)
{
seed ^= hash + 0x9e3779b9 + (seed << 6) + (seed >> 2);
}
inline std::size_t hashDouble(double value, std::size_t significantDigits)
{
return static_cast<std::size_t>(value * detail::RoundingFactor(significantDigits));
}
template<typename ElementType>
inline std::size_t hashVector3(const BasicVector3<ElementType>& v, std::size_t significantDigits)
{
auto xHash = math::hashDouble(v.x(), significantDigits);
auto yHash = math::hashDouble(v.y(), significantDigits);
auto zHash = math::hashDouble(v.z(), significantDigits);
math::combineHash(xHash, yHash);
math::combineHash(xHash, zHash);
return xHash;
}
// Convenience wrapper around the C-style functions in the SHA256.h header
class Hash
{
private:
std::unique_ptr<SHA256_CTX> _context;
public:
Hash() :
_context(new SHA256_CTX)
{
sha256_init(_context.get());
}
void addSizet(std::size_t value)
{
sha256_update(_context.get(), reinterpret_cast<const uint8_t*>(&value), sizeof(value));
}
void addDouble(double value, std::size_t significantDigits)
{
auto intValue = static_cast<std::size_t>(value * detail::RoundingFactor(significantDigits));
addSizet(intValue);
}
template<typename ElementType>
void addVector3(const BasicVector3<ElementType>& v, std::size_t significantDigits)
{
std::size_t components[3] =
{
static_cast<std::size_t>(v.x() * detail::RoundingFactor(significantDigits)),
static_cast<std::size_t>(v.y() * detail::RoundingFactor(significantDigits)),
static_cast<std::size_t>(v.z() * detail::RoundingFactor(significantDigits)),
};
sha256_update(_context.get(), reinterpret_cast<const uint8_t*>(&components), sizeof(components));
}
void addString(const std::string& str)
{
if (str.length() == 0) return;
sha256_update(_context.get(), reinterpret_cast<const uint8_t*>(str.data()), str.length());
}
operator std::string() const
{
uint8_t digest[SHA256_BLOCK_SIZE];
sha256_final(_context.get(), digest);
constexpr char hexChars[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
std::string hexString(sizeof(digest) * 2, '\0');
for (auto i = 0; i < sizeof(digest); ++i)
{
hexString[i*2] = hexChars[(digest[i] & 0xF0) >> 4];
hexString[i*2 + 1] = hexChars[digest[i] & 0x0F];
}
return hexString;
}
};
}
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