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1d42c4f6de
Per XLS-0095, we are taking steps to rename ripple(d) to xrpl(d). This change specifically removes all copyright notices referencing Ripple, XRPLF, and certain affiliated contributors upon mutual agreement, so the notice in the LICENSE.md file applies throughout. Copyright notices referencing external contributions remain as-is. Duplicate verbiage is also removed.
100 lines
1.9 KiB
C++
100 lines
1.9 KiB
C++
#ifndef BEAST_RANDOM_XOR_SHIFT_ENGINE_H_INCLUDED
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#define BEAST_RANDOM_XOR_SHIFT_ENGINE_H_INCLUDED
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#include <cstdint>
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#include <limits>
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#include <stdexcept>
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namespace beast {
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namespace detail {
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template <class = void>
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class xor_shift_engine
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{
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public:
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using result_type = std::uint64_t;
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xor_shift_engine(xor_shift_engine const&) = default;
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xor_shift_engine&
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operator=(xor_shift_engine const&) = default;
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explicit xor_shift_engine(result_type val = 1977u);
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void
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seed(result_type seed);
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result_type
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operator()();
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static result_type constexpr min()
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{
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return std::numeric_limits<result_type>::min();
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}
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static result_type constexpr max()
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{
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return std::numeric_limits<result_type>::max();
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}
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private:
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result_type s_[2];
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static result_type
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murmurhash3(result_type x);
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};
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template <class _>
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xor_shift_engine<_>::xor_shift_engine(result_type val)
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{
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seed(val);
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}
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template <class _>
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void
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xor_shift_engine<_>::seed(result_type seed)
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{
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if (seed == 0)
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throw std::domain_error("invalid seed");
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s_[0] = murmurhash3(seed);
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s_[1] = murmurhash3(s_[0]);
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}
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template <class _>
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auto
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xor_shift_engine<_>::operator()() -> result_type
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{
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result_type s1 = s_[0];
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result_type const s0 = s_[1];
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s_[0] = s0;
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s1 ^= s1 << 23;
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return (s_[1] = (s1 ^ s0 ^ (s1 >> 17) ^ (s0 >> 26))) + s0;
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}
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template <class _>
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auto
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xor_shift_engine<_>::murmurhash3(result_type x) -> result_type
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{
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x ^= x >> 33;
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x *= 0xff51afd7ed558ccdULL;
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x ^= x >> 33;
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x *= 0xc4ceb9fe1a85ec53ULL;
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return x ^= x >> 33;
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}
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} // namespace detail
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/** XOR-shift Generator.
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Meets the requirements of UniformRandomNumberGenerator.
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Simple and fast RNG based on:
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http://xorshift.di.unimi.it/xorshift128plus.c
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does not accept seed==0
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*/
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using xor_shift_engine = detail::xor_shift_engine<>;
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} // namespace beast
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#endif
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