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_DISCARD_BLOCK_ENGINE_H
10#define _LIBCPP___RANDOM_DISCARD_BLOCK_ENGINE_H
11
12#include <__config>
13#include <__random/is_seed_sequence.h>
14#include <__type_traits/enable_if.h>
15#include <__type_traits/is_convertible.h>
16#include <__utility/move.h>
17#include <cstddef>
18#include <iosfwd>
19#include <limits>
20
21#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
22#  pragma GCC system_header
23#endif
24
25_LIBCPP_PUSH_MACROS
26#include <__undef_macros>
27
28_LIBCPP_BEGIN_NAMESPACE_STD
29
30template <class _Engine, size_t __p, size_t __r>
31class _LIBCPP_TEMPLATE_VIS discard_block_engine {
32  _Engine __e_;
33  int __n_;
34
35  static_assert(0 < __r, "discard_block_engine invalid parameters");
36  static_assert(__r <= __p, "discard_block_engine invalid parameters");
37#ifndef _LIBCPP_CXX03_LANG // numeric_limits::max() is not constexpr in C++03
38  static_assert(__r <= numeric_limits<int>::max(), "discard_block_engine invalid parameters");
39#endif
40
41public:
42  // types
43  typedef typename _Engine::result_type result_type;
44
45  // engine characteristics
46  static _LIBCPP_CONSTEXPR const size_t block_size = __p;
47  static _LIBCPP_CONSTEXPR const size_t used_block = __r;
48
49#ifdef _LIBCPP_CXX03_LANG
50  static const result_type _Min = _Engine::_Min;
51  static const result_type _Max = _Engine::_Max;
52#else
53  static _LIBCPP_CONSTEXPR const result_type _Min = _Engine::min();
54  static _LIBCPP_CONSTEXPR const result_type _Max = _Engine::max();
55#endif
56
57  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type min() { return _Engine::min(); }
58  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type max() { return _Engine::max(); }
59
60  // constructors and seeding functions
61  _LIBCPP_HIDE_FROM_ABI discard_block_engine() : __n_(0) {}
62  _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(const _Engine& __e) : __e_(__e), __n_(0) {}
63#ifndef _LIBCPP_CXX03_LANG
64  _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(_Engine&& __e) : __e_(std::move(__e)), __n_(0) {}
65#endif // _LIBCPP_CXX03_LANG
66  _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(result_type __sd) : __e_(__sd), __n_(0) {}
67  template <
68      class _Sseq,
69      __enable_if_t<__is_seed_sequence<_Sseq, discard_block_engine>::value && !is_convertible<_Sseq, _Engine>::value,
70                    int> = 0>
71  _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(_Sseq& __q) : __e_(__q), __n_(0) {}
72  _LIBCPP_HIDE_FROM_ABI void seed() {
73    __e_.seed();
74    __n_ = 0;
75  }
76  _LIBCPP_HIDE_FROM_ABI void seed(result_type __sd) {
77    __e_.seed(__sd);
78    __n_ = 0;
79  }
80  template <class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, discard_block_engine>::value, int> = 0>
81  _LIBCPP_HIDE_FROM_ABI void seed(_Sseq& __q) {
82    __e_.seed(__q);
83    __n_ = 0;
84  }
85
86  // generating functions
87  _LIBCPP_HIDE_FROM_ABI result_type operator()();
88  _LIBCPP_HIDE_FROM_ABI void discard(unsigned long long __z) {
89    for (; __z; --__z)
90      operator()();
91  }
92
93  // property functions
94  _LIBCPP_HIDE_FROM_ABI const _Engine& base() const _NOEXCEPT { return __e_; }
95
96  template <class _Eng, size_t _Pp, size_t _Rp>
97  friend bool
98  operator==(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y);
99
100  template <class _Eng, size_t _Pp, size_t _Rp>
101  friend bool
102  operator!=(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y);
103
104  template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
105  friend basic_ostream<_CharT, _Traits>&
106  operator<<(basic_ostream<_CharT, _Traits>& __os, const discard_block_engine<_Eng, _Pp, _Rp>& __x);
107
108  template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
109  friend basic_istream<_CharT, _Traits>&
110  operator>>(basic_istream<_CharT, _Traits>& __is, discard_block_engine<_Eng, _Pp, _Rp>& __x);
111};
112
113template <class _Engine, size_t __p, size_t __r>
114_LIBCPP_CONSTEXPR const size_t discard_block_engine<_Engine, __p, __r>::block_size;
115
116template <class _Engine, size_t __p, size_t __r>
117_LIBCPP_CONSTEXPR const size_t discard_block_engine<_Engine, __p, __r>::used_block;
118
119template <class _Engine, size_t __p, size_t __r>
120typename discard_block_engine<_Engine, __p, __r>::result_type discard_block_engine<_Engine, __p, __r>::operator()() {
121  if (__n_ >= static_cast<int>(__r)) {
122    __e_.discard(__p - __r);
123    __n_ = 0;
124  }
125  ++__n_;
126  return __e_();
127}
128
129template <class _Eng, size_t _Pp, size_t _Rp>
130inline _LIBCPP_HIDE_FROM_ABI bool
131operator==(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y) {
132  return __x.__n_ == __y.__n_ && __x.__e_ == __y.__e_;
133}
134
135template <class _Eng, size_t _Pp, size_t _Rp>
136inline _LIBCPP_HIDE_FROM_ABI bool
137operator!=(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y) {
138  return !(__x == __y);
139}
140
141template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
142_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
143operator<<(basic_ostream<_CharT, _Traits>& __os, const discard_block_engine<_Eng, _Pp, _Rp>& __x) {
144  __save_flags<_CharT, _Traits> __lx(__os);
145  typedef basic_ostream<_CharT, _Traits> _Ostream;
146  __os.flags(_Ostream::dec | _Ostream::left);
147  _CharT __sp = __os.widen(' ');
148  __os.fill(__sp);
149  return __os << __x.__e_ << __sp << __x.__n_;
150}
151
152template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
153_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
154operator>>(basic_istream<_CharT, _Traits>& __is, discard_block_engine<_Eng, _Pp, _Rp>& __x) {
155  __save_flags<_CharT, _Traits> __lx(__is);
156  typedef basic_istream<_CharT, _Traits> _Istream;
157  __is.flags(_Istream::dec | _Istream::skipws);
158  _Eng __e;
159  int __n;
160  __is >> __e >> __n;
161  if (!__is.fail()) {
162    __x.__e_ = __e;
163    __x.__n_ = __n;
164  }
165  return __is;
166}
167
168_LIBCPP_END_NAMESPACE_STD
169
170_LIBCPP_POP_MACROS
171
172#endif // _LIBCPP___RANDOM_DISCARD_BLOCK_ENGINE_H
173