141 lines
3.4 KiB
C++
141 lines
3.4 KiB
C++
/*
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* mptRandom.h
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* -----------
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* Purpose: PRNG
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* Notes : (currently none)
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* Authors: OpenMPT Devs
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* The OpenMPT source code is released under the BSD license. Read LICENSE for more details.
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*/
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#pragma once
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#include "openmpt/all/BuildSettings.hpp"
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#include "mpt/base/bit.hpp"
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#include "mpt/mutex/mutex.hpp"
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#ifdef MODPLUG_TRACKER
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#include "mpt/random/crand.hpp"
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#endif // MODPLUG_TRACKER
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#include "mpt/random/default_engines.hpp"
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#include "mpt/random/device.hpp"
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#include "mpt/random/engine.hpp"
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#include "mpt/random/engine_lcg.hpp"
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#include "mpt/random/seed.hpp"
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#include <limits>
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#include <random>
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OPENMPT_NAMESPACE_BEGIN
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// NOTE:
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// We implement our own PRNG and distribution functions as the implementations
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// of std::uniform_int_distribution is either wrong (not uniform in MSVC2010) or
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// not guaranteed to be livelock-free for bad PRNGs (in GCC, Clang, boost).
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// We resort to a simpler implementation with only power-of-2 result ranges for
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// both the underlying PRNG and our interface function. This saves us from
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// complicated code having to deal with partial bits of entropy.
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// Our interface still somewhat follows the mindset of C++11 <random> (with the
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// addition of a simple wrapper function mpt::random which saves the caller from
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// instantiating distribution objects for the common uniform distribution case.
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// We are still using std::random_device for initial seeding when avalable and
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// after working around its set of problems.
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namespace mpt
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{
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template <typename Trng>
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class thread_safe_prng
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: private Trng
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{
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private:
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mpt::mutex m;
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public:
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typedef typename Trng::result_type result_type;
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public:
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template <typename Trd>
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explicit thread_safe_prng(Trd & rd)
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: Trng(mpt::make_prng<Trng>(rd))
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{
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return;
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}
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thread_safe_prng(Trng rng)
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: Trng(rng)
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{
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return;
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}
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public:
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static MPT_CONSTEXPRINLINE typename engine_traits<Trng>::result_type min()
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{
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return Trng::min();
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}
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static MPT_CONSTEXPRINLINE typename engine_traits<Trng>::result_type max()
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{
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return Trng::max();
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}
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static MPT_CONSTEXPRINLINE int result_bits()
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{
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return engine_traits<Trng>::result_bits();
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}
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public:
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typename engine_traits<Trng>::result_type operator()()
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{
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mpt::lock_guard<mpt::mutex> l(m);
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return Trng::operator()();
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}
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};
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#ifdef MPT_BUILD_FUZZER
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// Use deterministic seeding
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using random_device = deterministc_random_device;
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#else // !MPT_BUILD_FUZZER
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// mpt::random_device always generates 32 bits of entropy
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using random_device = mpt::sane_random_device;
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#endif // MPT_BUILD_FUZZER
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#ifdef MPT_BUILD_FUZZER
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// Use fast PRNGs in order to not waste time fuzzing more complex PRNG
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// implementations.
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using fast_prng = deterministic_fast_engine;
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using good_prng = deterministic_good_engine;
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#else // !MPT_BUILD_FUZZER
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// We cannot use std::minstd_rand here because it has not a power-of-2 sized
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// output domain which we rely upon.
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using fast_prng = fast_engine; // about 3 ALU operations, ~32bit of state, suited for inner loops
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using good_prng = good_engine;
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#endif // MPT_BUILD_FUZZER
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using default_prng = mpt::good_prng;
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mpt::random_device & global_random_device();
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mpt::thread_safe_prng<mpt::default_prng> & global_prng();
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#if defined(MODPLUG_TRACKER) && !defined(MPT_BUILD_WINESUPPORT)
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void set_global_random_device(mpt::random_device *rd);
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void set_global_prng(mpt::thread_safe_prng<mpt::default_prng> *rng);
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#endif // MODPLUG_TRACKER && !MPT_BUILD_WINESUPPORT
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} // namespace mpt
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OPENMPT_NAMESPACE_END
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