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// xorshift64star.h
// this file is part of Context Free
// ---------------------
// Copyright (C) 2015 John Horigan - john@glyphic.com
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
// John Horigan can be contacted at john@glyphic.com or at
// John Horigan, 1209 Villa St., Mountain View, CA 94041-1123, USA
//
//
#ifndef INCLUDE_XORSHIFT64STAR_H
#define INCLUDE_XORSHIFT64STAR_H
#include <cstdint>
#include <limits>
#include <random>
#include <istream>
#include <ostream>
#if defined(_MSC_VER) && _MSC_VER < 1900
#define myConstExpr
#else
#define myConstExpr constexpr
#endif
// This class implements the xorshift64* PRNG.
class XORshift64star {
public:
using result_type = std::uint64_t;
enum e_consts : result_type {
RAND64_MULT = 2685821657736338717ULL,
RAND64_SEED = 0x3DF41234ABCD330EULL
};
result_type mSeed;
explicit XORshift64star(result_type _s = RAND64_SEED) : mSeed(_s ? _s : RAND64_SEED) { }
template <class SSeq>
explicit XORshift64star(SSeq& q) { seed(q); }
void seed(result_type _s = RAND64_SEED) { mSeed = _s ? _s : RAND64_SEED; }
template <class SSeq>
void seed(SSeq& q)
{
std::uint32_t seeds[2];
q.generate(seeds, seeds+2);
mSeed = static_cast<result_type>(seeds[0]) << 32 |
static_cast<result_type>(seeds[1]);
if (mSeed == 0)
mSeed = RAND64_SEED;
}
void discard(unsigned long long z)
{
for (unsigned long long i = 0; i < z; ++i) {
// This is the xorshift64* PRNG.
mSeed ^= mSeed >> 12;
mSeed ^= mSeed << 25;
mSeed ^= mSeed >> 27;
}
}
result_type operator()()
{
result_type result = mSeed * RAND64_MULT;
discard(1);
return result;
}
static myConstExpr result_type min() { return 1; }
static myConstExpr result_type max() { return static_cast<result_type>(-1LL); }
bool operator==(const XORshift64star& rhs) const { return mSeed == rhs.mSeed; }
bool operator!=(const XORshift64star& rhs) const { return mSeed != rhs.mSeed; }
template <class CharT, class Traits>
friend std::basic_ostream<CharT,Traits>& operator<<(std::basic_ostream<CharT,Traits>& ost, const XORshift64star& rhs);
template <class CharT, class Traits>
friend std::basic_istream<CharT,Traits>& operator>>(std::basic_istream<CharT,Traits>& ist, XORshift64star& rhs);
private:
template <class _CharT, class _Traits>
class _save_flags
{
using _stream_type = std::basic_ios<_CharT, _Traits>;
using fmtflags = typename _stream_type::fmtflags;
_stream_type& _stream_;
fmtflags _fmtflags_;
_CharT _fill_;
_save_flags(const _save_flags&);
_save_flags& operator=(const _save_flags&);
public:
explicit _save_flags(_stream_type& _stream)
: _stream_(_stream),
_fmtflags_(_stream.flags()),
_fill_(_stream.fill())
{}
~_save_flags()
{
_stream_.flags(_fmtflags_);
_stream_.fill(_fill_);
}
};
};
template <class CharT, class Traits>
std::basic_ostream<CharT,Traits>& operator<<(std::basic_ostream<CharT,Traits>& ost, const XORshift64star& rhs)
{
XORshift64star::_save_flags<CharT, Traits> lx(ost);
ost.flags(std::ios_base::dec | std::ios_base::left);
ost.fill(ost.widen(' '));
return ost << rhs.mSeed;
}
template <class CharT, class Traits>
std::basic_istream<CharT,Traits>& operator>>(std::basic_istream<CharT,Traits>& ist, XORshift64star& rhs)
{
XORshift64star::_save_flags<CharT, Traits> lx(ist);
ist.flags(std::ios_base::dec | std::ios_base::skipws);
XORshift64star::result_type tmp;
ist >> tmp;
if (!ist.fail())
rhs.mSeed = tmp;
return ist;
}
#endif // INCLUDE_XORSHIFT64STAR_H
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