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
29template <class _RealType, size_t __bits, class _URNG>
30_LIBCPP_HIDE_FROM_ABI _RealType generate_canonical(_URNG& __g) {
31  const size_t __dt = numeric_limits<_RealType>::digits;
32  const size_t __b  = __dt < __bits ? __dt : __bits;
33#ifdef _LIBCPP_CXX03_LANG
34  const size_t __log_r = __log2<uint64_t, _URNG::_Max - _URNG::_Min + uint64_t(1)>::value;
35#else
36  const size_t __log_r = __log2<uint64_t, _URNG::max() - _URNG::min() + uint64_t(1)>::value;
37#endif
38  const size_t __k     = __b / __log_r + (__b % __log_r != 0) + (__b == 0);
39  const _RealType __rp = static_cast<_RealType>(_URNG::max() - _URNG::min()) + _RealType(1);
40  _RealType __base     = __rp;
41  _RealType __sp       = __g() - _URNG::min();
42  for (size_t __i = 1; __i < __k; ++__i, __base *= __rp)
43    __sp += (__g() - _URNG::min()) * __base;
44  return __sp / __base;
45}
46
47_LIBCPP_END_NAMESPACE_STD
48
49_LIBCPP_POP_MACROS
50
51#endif // _LIBCPP___RANDOM_GENERATE_CANONICAL_H
52