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llvm-project/libcxx/include/__random/uniform_int_distribution.h

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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___RANDOM_UNIFORM_INT_DISTRIBUTION_H
#define _LIBCPP___RANDOM_UNIFORM_INT_DISTRIBUTION_H
#include <__bits>
#include <__config>
#include <__random/log2.h>
#include <bit>
#include <cstddef>
#include <cstdint>
#include <iosfwd>
#include <limits>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
template<class _Engine, class _UIntType>
class __independent_bits_engine
{
public:
// types
typedef _UIntType result_type;
private:
typedef typename _Engine::result_type _Engine_result_type;
typedef typename conditional
<
sizeof(_Engine_result_type) <= sizeof(result_type),
result_type,
_Engine_result_type
>::type _Working_result_type;
_Engine& __e_;
size_t __w_;
size_t __w0_;
size_t __n_;
size_t __n0_;
_Working_result_type __y0_;
_Working_result_type __y1_;
_Engine_result_type __mask0_;
_Engine_result_type __mask1_;
#ifdef _LIBCPP_CXX03_LANG
static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min
+ _Working_result_type(1);
#else
static _LIBCPP_CONSTEXPR const _Working_result_type _Rp = _Engine::max() - _Engine::min()
+ _Working_result_type(1);
#endif
static _LIBCPP_CONSTEXPR const size_t __m = __log2<_Working_result_type, _Rp>::value;
static _LIBCPP_CONSTEXPR const size_t _WDt = numeric_limits<_Working_result_type>::digits;
static _LIBCPP_CONSTEXPR const size_t _EDt = numeric_limits<_Engine_result_type>::digits;
public:
// constructors and seeding functions
__independent_bits_engine(_Engine& __e, size_t __w);
// generating functions
result_type operator()() {return __eval(integral_constant<bool, _Rp != 0>());}
private:
result_type __eval(false_type);
result_type __eval(true_type);
};
template<class _Engine, class _UIntType>
__independent_bits_engine<_Engine, _UIntType>
::__independent_bits_engine(_Engine& __e, size_t __w)
: __e_(__e),
__w_(__w)
{
__n_ = __w_ / __m + (__w_ % __m != 0);
__w0_ = __w_ / __n_;
if (_Rp == 0)
__y0_ = _Rp;
else if (__w0_ < _WDt)
__y0_ = (_Rp >> __w0_) << __w0_;
else
__y0_ = 0;
if (_Rp - __y0_ > __y0_ / __n_)
{
++__n_;
__w0_ = __w_ / __n_;
if (__w0_ < _WDt)
__y0_ = (_Rp >> __w0_) << __w0_;
else
__y0_ = 0;
}
__n0_ = __n_ - __w_ % __n_;
if (__w0_ < _WDt - 1)
__y1_ = (_Rp >> (__w0_ + 1)) << (__w0_ + 1);
else
__y1_ = 0;
__mask0_ = __w0_ > 0 ? _Engine_result_type(~0) >> (_EDt - __w0_) :
_Engine_result_type(0);
__mask1_ = __w0_ < _EDt - 1 ?
_Engine_result_type(~0) >> (_EDt - (__w0_ + 1)) :
_Engine_result_type(~0);
}
template<class _Engine, class _UIntType>
inline
_UIntType
__independent_bits_engine<_Engine, _UIntType>::__eval(false_type)
{
return static_cast<result_type>(__e_() & __mask0_);
}
template<class _Engine, class _UIntType>
_UIntType
__independent_bits_engine<_Engine, _UIntType>::__eval(true_type)
{
const size_t _WRt = numeric_limits<result_type>::digits;
result_type _Sp = 0;
for (size_t __k = 0; __k < __n0_; ++__k)
{
_Engine_result_type __u;
do
{
__u = __e_() - _Engine::min();
} while (__u >= __y0_);
if (__w0_ < _WRt)
_Sp <<= __w0_;
else
_Sp = 0;
_Sp += __u & __mask0_;
}
for (size_t __k = __n0_; __k < __n_; ++__k)
{
_Engine_result_type __u;
do
{
__u = __e_() - _Engine::min();
} while (__u >= __y1_);
if (__w0_ < _WRt - 1)
_Sp <<= __w0_ + 1;
else
_Sp = 0;
_Sp += __u & __mask1_;
}
return _Sp;
}
template<class _IntType = int> // __int128_t is also supported as an extension here
class uniform_int_distribution
{
public:
// types
typedef _IntType result_type;
class param_type
{
result_type __a_;
result_type __b_;
public:
typedef uniform_int_distribution distribution_type;
explicit param_type(result_type __a = 0,
result_type __b = numeric_limits<result_type>::max())
: __a_(__a), __b_(__b) {}
result_type a() const {return __a_;}
result_type b() const {return __b_;}
friend bool operator==(const param_type& __x, const param_type& __y)
{return __x.__a_ == __y.__a_ && __x.__b_ == __y.__b_;}
friend bool operator!=(const param_type& __x, const param_type& __y)
{return !(__x == __y);}
};
private:
param_type __p_;
public:
// constructors and reset functions
#ifndef _LIBCPP_CXX03_LANG
uniform_int_distribution() : uniform_int_distribution(0) {}
explicit uniform_int_distribution(
result_type __a, result_type __b = numeric_limits<result_type>::max())
: __p_(param_type(__a, __b)) {}
#else
explicit uniform_int_distribution(
result_type __a = 0,
result_type __b = numeric_limits<result_type>::max())
: __p_(param_type(__a, __b)) {}
#endif
explicit uniform_int_distribution(const param_type& __p) : __p_(__p) {}
void reset() {}
// generating functions
template<class _URNG> result_type operator()(_URNG& __g)
{return (*this)(__g, __p_);}
template<class _URNG> result_type operator()(_URNG& __g, const param_type& __p);
// property functions
result_type a() const {return __p_.a();}
result_type b() const {return __p_.b();}
param_type param() const {return __p_;}
void param(const param_type& __p) {__p_ = __p;}
result_type min() const {return a();}
result_type max() const {return b();}
friend bool operator==(const uniform_int_distribution& __x,
const uniform_int_distribution& __y)
{return __x.__p_ == __y.__p_;}
friend bool operator!=(const uniform_int_distribution& __x,
const uniform_int_distribution& __y)
{return !(__x == __y);}
};
template<class _IntType>
template<class _URNG>
typename uniform_int_distribution<_IntType>::result_type
uniform_int_distribution<_IntType>::operator()(_URNG& __g, const param_type& __p)
_LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
{
typedef typename conditional<sizeof(result_type) <= sizeof(uint32_t), uint32_t,
typename make_unsigned<result_type>::type>::type _UIntType;
const _UIntType _Rp = _UIntType(__p.b()) - _UIntType(__p.a()) + _UIntType(1);
if (_Rp == 1)
return __p.a();
const size_t _Dt = numeric_limits<_UIntType>::digits;
typedef __independent_bits_engine<_URNG, _UIntType> _Eng;
if (_Rp == 0)
return static_cast<result_type>(_Eng(__g, _Dt)());
size_t __w = _Dt - __countl_zero(_Rp) - 1;
if ((_Rp & (numeric_limits<_UIntType>::max() >> (_Dt - __w))) != 0)
++__w;
_Eng __e(__g, __w);
_UIntType __u;
do
{
__u = __e();
} while (__u >= _Rp);
return static_cast<result_type>(__u + __p.a());
}
template <class _CharT, class _Traits, class _IT>
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const uniform_int_distribution<_IT>& __x)
{
__save_flags<_CharT, _Traits> __lx(__os);
typedef basic_ostream<_CharT, _Traits> _Ostream;
__os.flags(_Ostream::dec | _Ostream::left);
_CharT __sp = __os.widen(' ');
__os.fill(__sp);
return __os << __x.a() << __sp << __x.b();
}
template <class _CharT, class _Traits, class _IT>
basic_istream<_CharT, _Traits>&
operator>>(basic_istream<_CharT, _Traits>& __is,
uniform_int_distribution<_IT>& __x)
{
typedef uniform_int_distribution<_IT> _Eng;
typedef typename _Eng::result_type result_type;
typedef typename _Eng::param_type param_type;
__save_flags<_CharT, _Traits> __lx(__is);
typedef basic_istream<_CharT, _Traits> _Istream;
__is.flags(_Istream::dec | _Istream::skipws);
result_type __a;
result_type __b;
__is >> __a >> __b;
if (!__is.fail())
__x.param(param_type(__a, __b));
return __is;
}
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___RANDOM_UNIFORM_INT_DISTRIBUTION_H
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