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___RANDOM_GENERATE_CANONICAL_H
10 #define _LIBCPP___RANDOM_GENERATE_CANONICAL_H
11 
12 #include <__config>
13 #include <__random/log2.h>
14 #include <cstdint>
15 #include <initializer_list>
16 #include <limits>
17 
18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19 #  pragma GCC system_header
20 #endif
21 
22 _LIBCPP_PUSH_MACROS
23 #include <__undef_macros>
24 
25 _LIBCPP_BEGIN_NAMESPACE_STD
26 
27 // generate_canonical
28 
29 template<class _RealType, size_t __bits, class _URNG>
30 _RealType
31 generate_canonical(_URNG& __g)
32 {
33     const size_t _Dt = numeric_limits<_RealType>::digits;
34     const size_t __b = _Dt < __bits ? _Dt : __bits;
35 #ifdef _LIBCPP_CXX03_LANG
36     const size_t __logR = __log2<uint64_t, _URNG::_Max - _URNG::_Min + uint64_t(1)>::value;
37 #else
38     const size_t __logR = __log2<uint64_t, _URNG::max() - _URNG::min() + uint64_t(1)>::value;
39 #endif
40     const size_t __k = __b / __logR + (__b % __logR != 0) + (__b == 0);
41     const _RealType _Rp = static_cast<_RealType>(_URNG::max() - _URNG::min()) + _RealType(1);
42     _RealType __base = _Rp;
43     _RealType _Sp = __g() - _URNG::min();
44     for (size_t __i = 1; __i < __k; ++__i, __base *= _Rp)
45         _Sp += (__g() - _URNG::min()) * __base;
46     return _Sp / __base;
47 }
48 
49 _LIBCPP_END_NAMESPACE_STD
50 
51 _LIBCPP_POP_MACROS
52 
53 #endif // _LIBCPP___RANDOM_GENERATE_CANONICAL_H
54