1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef _LIBCPP___CXX03___RANDOM_GENERATE_CANONICAL_H 10 #define _LIBCPP___CXX03___RANDOM_GENERATE_CANONICAL_H 11 12 #include <__cxx03/__config> 13 #include <__cxx03/__random/log2.h> 14 #include <__cxx03/cstdint> 15 #include <__cxx03/limits> 16 17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 18 # pragma GCC system_header 19 #endif 20 21 _LIBCPP_PUSH_MACROS 22 #include <__cxx03/__undef_macros> 23 24 _LIBCPP_BEGIN_NAMESPACE_STD 25 26 // generate_canonical 27 28 template <class _RealType, size_t __bits, class _URNG> generate_canonical(_URNG & __g)29_LIBCPP_HIDE_FROM_ABI _RealType generate_canonical(_URNG& __g) { 30 const size_t __dt = numeric_limits<_RealType>::digits; 31 const size_t __b = __dt < __bits ? __dt : __bits; 32 const size_t __log_r = __log2<uint64_t, _URNG::_Max - _URNG::_Min + uint64_t(1)>::value; 33 const size_t __k = __b / __log_r + (__b % __log_r != 0) + (__b == 0); 34 const _RealType __rp = static_cast<_RealType>(_URNG::max() - _URNG::min()) + _RealType(1); 35 _RealType __base = __rp; 36 _RealType __sp = __g() - _URNG::min(); 37 for (size_t __i = 1; __i < __k; ++__i, __base *= __rp) 38 __sp += (__g() - _URNG::min()) * __base; 39 return __sp / __base; 40 } 41 42 _LIBCPP_END_NAMESPACE_STD 43 44 _LIBCPP_POP_MACROS 45 46 #endif // _LIBCPP___CXX03___RANDOM_GENERATE_CANONICAL_H 47