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 _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>
114typename discard_block_engine<_Engine, __p, __r>::result_type discard_block_engine<_Engine, __p, __r>::operator()() {
115 if (__n_ >= static_cast<int>(__r)) {
116 __e_.discard(__p - __r);
117 __n_ = 0;
118 }
119 ++__n_;
120 return __e_();
121}
122
123template <class _Eng, size_t _Pp, size_t _Rp>
124inline _LIBCPP_HIDE_FROM_ABI bool
125operator==(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y) {
126 return __x.__n_ == __y.__n_ && __x.__e_ == __y.__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 == __y);
133}
134
135template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
136_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
137operator<<(basic_ostream<_CharT, _Traits>& __os, const discard_block_engine<_Eng, _Pp, _Rp>& __x) {
138 __save_flags<_CharT, _Traits> __lx(__os);
139 typedef basic_ostream<_CharT, _Traits> _Ostream;
140 __os.flags(_Ostream::dec | _Ostream::left);
141 _CharT __sp = __os.widen(' ');
142 __os.fill(__sp);
143 return __os << __x.__e_ << __sp << __x.__n_;
144}
145
146template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
147_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
148operator>>(basic_istream<_CharT, _Traits>& __is, discard_block_engine<_Eng, _Pp, _Rp>& __x) {
149 __save_flags<_CharT, _Traits> __lx(__is);
150 typedef basic_istream<_CharT, _Traits> _Istream;
151 __is.flags(_Istream::dec | _Istream::skipws);
152 _Eng __e;
153 int __n;
154 __is >> __e >> __n;
155 if (!__is.fail()) {
156 __x.__e_ = __e;
157 __x.__n_ = __n;
158 }
159 return __is;
160}
161
162_LIBCPP_END_NAMESPACE_STD
163
164_LIBCPP_POP_MACROS
165
166#endif // _LIBCPP___RANDOM_DISCARD_BLOCK_ENGINE_H
167