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 <__cstddef/size_t.h>
14#include <__random/is_seed_sequence.h>
15#include <__type_traits/enable_if.h>
16#include <__type_traits/is_convertible.h>
17#include <__utility/move.h>
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 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 inline _LIBCPP_CONSTEXPR const size_t block_size = __p;
47 static inline _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 constexpr result_type _Min = _Engine::min();
54 static constexpr result_type _Max = _Engine::max();
55#endif
56
57 [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type min() { return _Engine::min(); }
58 [[__nodiscard__]] _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 <class _Sseq,
68 __enable_if_t<__is_seed_sequence_v<_Sseq, discard_block_engine> && !is_convertible<_Sseq, _Engine>::value,
69 int> = 0>
70 _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(_Sseq& __q) : __e_(__q), __n_(0) {}
71 _LIBCPP_HIDE_FROM_ABI void seed() {
72 __e_.seed();
73 __n_ = 0;
74 }
75 _LIBCPP_HIDE_FROM_ABI void seed(result_type __sd) {
76 __e_.seed(__sd);
77 __n_ = 0;
78 }
79 template <class _Sseq, __enable_if_t<__is_seed_sequence_v<_Sseq, discard_block_engine>, int> = 0>
80 _LIBCPP_HIDE_FROM_ABI void seed(_Sseq& __q) {
81 __e_.seed(__q);
82 __n_ = 0;
83 }
84
85 // generating functions
86 [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI result_type operator()();
87 _LIBCPP_HIDE_FROM_ABI void discard(unsigned long long __z) {
88 for (; __z; --__z)
89 (void)operator()();
90 }
91
92 // property functions
93 [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const _Engine& base() const _NOEXCEPT { return __e_; }
94
95 template <class _Eng, size_t _Pp, size_t _Rp>
96 friend bool
97 operator==(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y);
98
99 template <class _Eng, size_t _Pp, size_t _Rp>
100 friend bool
101 operator!=(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y);
102
103 template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
104 friend basic_ostream<_CharT, _Traits>&
105 operator<<(basic_ostream<_CharT, _Traits>& __os, const discard_block_engine<_Eng, _Pp, _Rp>& __x);
106
107 template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
108 friend basic_istream<_CharT, _Traits>&
109 operator>>(basic_istream<_CharT, _Traits>& __is, discard_block_engine<_Eng, _Pp, _Rp>& __x);
110};
111
112template <class _Engine, size_t __p, size_t __r>
113typename discard_block_engine<_Engine, __p, __r>::result_type discard_block_engine<_Engine, __p, __r>::operator()() {
114 if (__n_ >= static_cast<int>(__r)) {
115 __e_.discard(__p - __r);
116 __n_ = 0;
117 }
118 ++__n_;
119 return __e_();
120}
121
122template <class _Eng, size_t _Pp, size_t _Rp>
123inline _LIBCPP_HIDE_FROM_ABI bool
124operator==(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y) {
125 return __x.__n_ == __y.__n_ && __x.__e_ == __y.__e_;
126}
127
128template <class _Eng, size_t _Pp, size_t _Rp>
129inline _LIBCPP_HIDE_FROM_ABI bool
130operator!=(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y) {
131 return !(__x == __y);
132}
133
134template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
135_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
136operator<<(basic_ostream<_CharT, _Traits>& __os, const discard_block_engine<_Eng, _Pp, _Rp>& __x) {
137 __save_flags<_CharT, _Traits> __lx(__os);
138 typedef basic_ostream<_CharT, _Traits> _Ostream;
139 __os.flags(_Ostream::dec | _Ostream::left);
140 _CharT __sp = __os.widen(' ');
141 __os.fill(__sp);
142 return __os << __x.__e_ << __sp << __x.__n_;
143}
144
145template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
146_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
147operator>>(basic_istream<_CharT, _Traits>& __is, discard_block_engine<_Eng, _Pp, _Rp>& __x) {
148 __save_flags<_CharT, _Traits> __lx(__is);
149 typedef basic_istream<_CharT, _Traits> _Istream;
150 __is.flags(_Istream::dec | _Istream::skipws);
151 _Eng __e;
152 int __n;
153 __is >> __e >> __n;
154 if (!__is.fail()) {
155 __x.__e_ = __e;
156 __x.__n_ = __n;
157 }
158 return __is;
159}
160
161_LIBCPP_END_NAMESPACE_STD
162
163_LIBCPP_POP_MACROS
164
165#endif // _LIBCPP___RANDOM_DISCARD_BLOCK_ENGINE_H
166