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38 lines
1.1 KiB
C++
38 lines
1.1 KiB
C++
#pragma once
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// TODO: replace with llarp
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#include <algorithm>
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#include <random>
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#include <cstring>
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#include <cstddef>
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template <typename Gen>
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void
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random_bytes(void* dest, size_t length, Gen&& rng)
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{
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using RNG = std::remove_reference_t<Gen>;
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using UInt = typename RNG::result_type;
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static_assert(std::is_same_v<UInt, uint32_t> || std::is_same_v<UInt, uint64_t>);
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static_assert(RNG::min() == 0 && RNG::max() == std::numeric_limits<UInt>::max());
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auto* d = reinterpret_cast<std::byte*>(dest);
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for (size_t o = 0; o < length; o += sizeof(UInt))
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{
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UInt x = rng();
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std::memcpy(d + o, &x, std::min(sizeof(UInt), length - o));
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}
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}
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// Returns an RNG with a fully seeded state from std::random_device
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template <typename RNG>
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RNG
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seeded()
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{
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constexpr size_t rd_draws =
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((RNG::state_size * sizeof(typename RNG::result_type) - 1) / sizeof(unsigned int) + 1);
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std::array<unsigned int, rd_draws> seed_data;
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std::generate(seed_data.begin(), seed_data.end(), std::random_device{});
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std::seed_seq seed(seed_data.begin(), seed_data.end());
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return RNG{seed};
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}
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