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#pragma once
#include <nall/serializer.hpp>
#include <nall/stdint.hpp>
namespace nall {
struct RandomNumberGenerator {
virtual auto seed(uint64_t) -> void = 0;
virtual auto operator()() -> uint64_t = 0;
virtual auto serialize(serializer&) -> void = 0;
};
//Galois LFSR using CRC64 polynomials
struct LinearFeedbackShiftRegisterGenerator : RandomNumberGenerator {
auto seed(uint64_t seed) -> void {
lfsr = seed;
for(unsigned n = 0; n < 8; n++) operator()();
}
auto operator()() -> uint64_t {
return lfsr = (lfsr >> 1) ^ (-(lfsr & 1) & crc64jones);
}
auto serialize(serializer& s) -> void {
s.integer(lfsr);
}
private:
static const uint64_t crc64ecma = 0x42f0e1eba9ea3693;
static const uint64_t crc64jones = 0xad93d23594c935a9;
uint64_t lfsr = crc64ecma;
};
inline auto random() -> uint64_t {
static LinearFeedbackShiftRegisterGenerator lfsr;
return lfsr();
}
}
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