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construct/include/ircd/rand.h
2021-02-27 13:01:02 -08:00

149 lines
2.9 KiB
C++

// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.
#pragma once
#define HAVE_IRCD_RAND_H
/// Some character set dictionaries
namespace ircd::rand::dict
{
extern const std::string alnum;
extern const std::string alpha;
extern const std::string upper;
extern const std::string lower;
extern const std::string numeric;
}
/// Tools for randomization
namespace ircd::rand
{
struct xoshiro256p;
// Interface state.
extern std::random_device device;
extern std::mt19937_64 mt;
// Random integer
uint64_t integer() noexcept;
uint64_t integer(const uint64_t &min, const uint64_t &max) noexcept; // inclusive
uint64_t integer(xoshiro256p &);
// Random vector
template<class T> T vector() noexcept = delete;
template<> u128x1 vector() noexcept;
template<> u256x1 vector() noexcept;
template<> u512x1 vector() noexcept;
// Random vector over distribution
template<class T,
class distribution>
T vector(distribution &);
// Random fill of buffer
const_buffer fill(const mutable_buffer &out) noexcept;
// Random fill of array
template<class T,
size_t S>
decltype(auto) fill(T (&buf)[S]);
// Random character from dictionary
char character(const std::string &dict = dict::alnum);
// Random string from dictionary, fills buffer
string_view string(const mutable_buffer &out, const std::string &dict) noexcept;
}
struct ircd::rand::xoshiro256p
{
uint64_t s[4];
xoshiro256p();
};
template<class T,
size_t S>
inline decltype(auto)
ircd::rand::fill(T (&buf)[S])
{
static_assert
(
sizeof(buf) == sizeof(T) * S
);
const mutable_buffer mb
{
reinterpret_cast<char *>(buf), sizeof(buf)
};
fill(mb);
return buf;
}
/// Random character from dictionary
inline char
ircd::rand::character(const std::string &dict)
{
assert(!dict.empty());
const auto pos
{
integer(0, dict.size() - 1)
};
assert(pos < dict.size());
return dict[pos];
}
template<class T,
class distribution>
inline T
ircd::rand::vector(distribution &dist)
{
constexpr auto lanes
{
simd::lanes<T>()
};
T ret;
for(unsigned i(0); i < lanes; ++i)
ret[i] = dist(mt);
return ret;
}
inline
ircd::rand::xoshiro256p::xoshiro256p()
{
fill(s);
}
inline uint64_t
ircd::rand::integer(xoshiro256p &state)
{
auto &s(state.s);
const u64
ret(s[0] + s[3]),
t(s[1] << 17);
s[2] ^= s[0];
s[3] ^= s[1];
s[1] ^= s[2];
s[0] ^= s[3];
s[2] ^= t;
#if __has_builtin(__builtin_rotateleft64)
s[3] = __builtin_rotateleft64(s[3], 45);
#else
s[3] = (s[3] << 45) | (s[3] >> (64 - 45));
#endif
return ret;
}