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54 lines
2.2 KiB
54 lines
2.2 KiB
#pragma once
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#include <bit>
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#include <array>
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#include <cstdint>
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#include "util.hh"
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#include "exopt.h"
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namespace exopt::rng {
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[[gnu::visibility("internal")]]
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constexpr inline auto COMPILED_ENTROPY{
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#if __has_include("compiled_entropy.dat")
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#embed "compiled_entropy.dat"
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#else
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nullptr
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#endif
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};
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constexpr inline auto has_compiled_entropy_v = !std::is_same_v<std::nullptr_t, decltype(COMPILED_ENTROPY)>;
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// XXX: The usage of __COUNTER__ *might* work as wanted if we wrap it in _EO_CONSTANT_VALUE() and take `util::comptime<uint64_t> auto = _EO_CONSTANT_VALUE(__COUNTER__)` as default argument instead. Maybe... I don't know..
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template<typename T = unsigned char>
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consteval decltype(auto) comptime_rand_next() noexcept {
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std::array<unsigned char, sizeof(T)> v;
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for(int i=0;i<v.size();i++) v[i] = comptime_rand_next<unsigned char>();
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return util::comptime_value(std::bit_cast<T>(std::move(v)));
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}
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template<>
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consteval decltype(auto) comptime_rand_next<unsigned char>(uint64_t counter = __COUNTER__) noexcept {
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return _EO_CONSTANT_VALUE(COMPILED_ENTROPY[counter % sizeof(COMPILED_ENTROPY)]);
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}
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consteval uint64_t seed_linear(uint64_t counter = __COUNTER__) noexcept { return uint64_t(counter); } //XXX: This is kinda a dumb experiment, the __TIME__ TU-specific seed should be fine, but __COUNTER__ is a token evaluated regardless of calling context, so... Unless it's used before the #include<>, it'll always be the same.
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consteval uint64_t seed_translation() noexcept { return uint64_t(__TIME__); }
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// Seed: __TIME__ or __COUNTER__
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[[gnu::const]]
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constexpr uint64_t splitmix64_once(uint64_t x) noexcept {
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//TODO: implement splitmix64 here for constexpr/consteval contexts
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}
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constexpr inline uint64_t translation_unit_fixed_seed = splitmit64_once(seed_translation());
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constexpr inline uint64_t linear_fixed_seed = splitmit64_once(seed_linear()); // ODR dependant?? When is __COUNTER__ evaluated? In preprocessing, right? So, before any compilation?
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constexpr inline auto translation_unit_rolling_seed = ([] () {
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struct {
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constexpr operator uint64_t() const noexcept { return splitmix64_once(translation_unit_fixed_seed ^ seed_linear()) ^ _EO_CONSTANT_VALUE(splitmix64_once(__COUNTER__)); }
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} inner;
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return inner;
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})();
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}
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