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Created May 28, 2018 02:40
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A C++ Implementation of Bob Jenkins's Small Fast Noncryptographic PRNG (JSF)
#ifndef JSF_HPP_INCLUDED
#define JSF_HPP_INCLUDED 1
/*
* A C++ implementation of a Bob Jenkins Small Fast (Noncryptographic) PRNGs
*
* The MIT License (MIT)
*
* Copyright (c) 2018 Melissa E. O'Neill
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
/* Based on code published by Bob Jenkins in 2007, adapted for C++ */
#include <cstdint>
namespace jsf_detail {
template <typename itype, typename rtype,
unsigned int p, unsigned int q, unsigned int r>
class jsf {
protected:
itype a_, b_, c_, d_;
static constexpr unsigned int ITYPE_BITS = 8*sizeof(itype);
static constexpr unsigned int RTYPE_BITS = 8*sizeof(rtype);
static itype rotate(itype x, unsigned int k)
{
return (x << k) | (x >> (ITYPE_BITS - k));
}
public:
using result_type = rtype;
using state_type = itype;
static constexpr result_type min() { return 0; }
static constexpr result_type max() { return ~ result_type(0); }
jsf(itype seed = itype(0xcafe5eed00000001ULL))
: a_(0xf1ea5eed), b_(seed), c_(seed), d_(seed)
{
for (unsigned int i=0; i<20; ++i)
advance();
}
void advance()
{
itype e = a_ - rotate(b_, p);
a_ = b_ ^ rotate(c_, q);
b_ = c_ + (r ? rotate(d_, r) : d_);
c_ = d_ + e;
d_ = e + a_;
}
rtype operator()()
{
advance();
return rtype(d_);
}
bool operator==(const jsf& rhs)
{
return (a_ == rhs.a_) && (b_ == rhs.b_)
&& (c_ == rhs.c_) && (d_ == rhs.d_);
}
bool operator!=(const jsf& rhs)
{
return !operator==(rhs);
}
// Not (yet) implemented:
// - arbitrary jumpahead (doable, but annoying to write).
// - I/O
// - Seeding from a seed_seq.
};
} // end namespace
///// ---- Specific JSF Generators ---- ////
//
// Each size has variations corresponding to different parameter sets.
// Each variant will create a distinct (and hopefully statistically
// independent) sequence.
//
// - 128 state bits, 32-bit output
//
// The constants are all those suggested by Bob Jenkins. The n variants
// perform only two rotations, the r variants perform three.
using jsf32na = jsf_detail::jsf<uint32_t, uint32_t, 27, 17, 0>;
using jsf32nb = jsf_detail::jsf<uint32_t, uint32_t, 9, 16, 0>;
using jsf32nc = jsf_detail::jsf<uint32_t, uint32_t, 9, 24, 0>;
using jsf32nd = jsf_detail::jsf<uint32_t, uint32_t, 10, 16, 0>;
using jsf32ne = jsf_detail::jsf<uint32_t, uint32_t, 10, 24, 0>;
using jsf32nf = jsf_detail::jsf<uint32_t, uint32_t, 11, 16, 0>;
using jsf32ng = jsf_detail::jsf<uint32_t, uint32_t, 11, 24, 0>;
using jsf32nh = jsf_detail::jsf<uint32_t, uint32_t, 25, 8, 0>;
using jsf32ni = jsf_detail::jsf<uint32_t, uint32_t, 25, 16, 0>;
using jsf32nj = jsf_detail::jsf<uint32_t, uint32_t, 26, 8, 0>;
using jsf32nk = jsf_detail::jsf<uint32_t, uint32_t, 26, 16, 0>;
using jsf32nl = jsf_detail::jsf<uint32_t, uint32_t, 26, 17, 0>;
using jsf32nm = jsf_detail::jsf<uint32_t, uint32_t, 27, 16, 0>;
using jsf32ra = jsf_detail::jsf<uint32_t, uint32_t, 3, 14, 24>;
using jsf32rb = jsf_detail::jsf<uint32_t, uint32_t, 3, 25, 15>;
using jsf32rc = jsf_detail::jsf<uint32_t, uint32_t, 4, 15, 24>;
using jsf32rd = jsf_detail::jsf<uint32_t, uint32_t, 6, 16, 28>;
using jsf32re = jsf_detail::jsf<uint32_t, uint32_t, 7, 16, 27>;
using jsf32rf = jsf_detail::jsf<uint32_t, uint32_t, 8, 14, 3>;
using jsf32rg = jsf_detail::jsf<uint32_t, uint32_t, 11, 16, 23>;
using jsf32rh = jsf_detail::jsf<uint32_t, uint32_t, 12, 16, 22>;
using jsf32ri = jsf_detail::jsf<uint32_t, uint32_t, 12, 17, 23>;
using jsf32rj = jsf_detail::jsf<uint32_t, uint32_t, 13, 16, 22>;
using jsf32rk = jsf_detail::jsf<uint32_t, uint32_t, 15, 25, 3>;
using jsf32rl = jsf_detail::jsf<uint32_t, uint32_t, 16, 9, 3>;
using jsf32rm = jsf_detail::jsf<uint32_t, uint32_t, 17, 9, 3>;
using jsf32rn = jsf_detail::jsf<uint32_t, uint32_t, 17, 27, 7>;
using jsf32ro = jsf_detail::jsf<uint32_t, uint32_t, 19, 7, 3>;
using jsf32rp = jsf_detail::jsf<uint32_t, uint32_t, 23, 15, 11>;
using jsf32rq = jsf_detail::jsf<uint32_t, uint32_t, 23, 16, 11>;
using jsf32rr = jsf_detail::jsf<uint32_t, uint32_t, 23, 17, 11>;
using jsf32rs = jsf_detail::jsf<uint32_t, uint32_t, 24, 3, 16>;
using jsf32rt = jsf_detail::jsf<uint32_t, uint32_t, 24, 4, 16>;
using jsf32ru = jsf_detail::jsf<uint32_t, uint32_t, 25, 14, 3>;
using jsf32rv = jsf_detail::jsf<uint32_t, uint32_t, 27, 16, 6>;
using jsf32rw = jsf_detail::jsf<uint32_t, uint32_t, 27, 16, 7>;
using jsf32n = jsf32na;
using jsf32r = jsf32rq;
using jsf32 = jsf32n;
// - 256 state bits, uint64_t output
using jsf64na = jsf_detail::jsf<uint64_t, uint64_t, 39, 11, 0>;
using jsf64ra = jsf_detail::jsf<uint64_t, uint64_t, 7, 13, 37>;
using jsf64n = jsf64na;
using jsf64r = jsf64ra;
using jsf64 = jsf64r;
// TINY VERSIONS FOR TESTING AND SPECIALIZED USES ONLY
//
// Parameters derived using a variant of rngav.c, originally written by
// Bob Jenkins.
// - 64 state bits, uint16_t output
using jsf16na = jsf_detail::jsf<uint16_t, uint16_t, 13, 8, 0>;
using jsf16 = jsf16na;
// - 32 state bits, uint8_t output
using jsf8na = jsf_detail::jsf<uint8_t, uint8_t, 1, 4, 0>;
using jsf8 = jsf8na;
#endif // JSF_HPP_INCLUDED
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