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 
30 template<class _Engine, size_t __p, size_t __r>
31 class _LIBCPP_TEMPLATE_VIS discard_block_engine
32 {
33     _Engine __e_;
34     int     __n_;
35 
36     static_assert(  0 <  __r, "discard_block_engine invalid parameters");
37     static_assert(__r <= __p, "discard_block_engine invalid parameters");
38 #ifndef _LIBCPP_CXX03_LANG // numeric_limits::max() is not constexpr in C++03
39     static_assert(__r <= numeric_limits<int>::max(), "discard_block_engine invalid parameters");
40 #endif
41 public:
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_INLINE_VISIBILITY
58     static _LIBCPP_CONSTEXPR result_type min() { return _Engine::min(); }
59     _LIBCPP_INLINE_VISIBILITY
60     static _LIBCPP_CONSTEXPR result_type max() { return _Engine::max(); }
61 
62     // constructors and seeding functions
63     _LIBCPP_INLINE_VISIBILITY
64     discard_block_engine() : __n_(0) {}
65     _LIBCPP_INLINE_VISIBILITY
66     explicit discard_block_engine(const _Engine& __e)
67         : __e_(__e), __n_(0) {}
68 #ifndef _LIBCPP_CXX03_LANG
69     _LIBCPP_INLINE_VISIBILITY
70     explicit discard_block_engine(_Engine&& __e)
71         : __e_(_VSTD::move(__e)), __n_(0) {}
72 #endif // _LIBCPP_CXX03_LANG
73     _LIBCPP_INLINE_VISIBILITY
74     explicit discard_block_engine(result_type __sd) : __e_(__sd), __n_(0) {}
75     template<class _Sseq>
76         _LIBCPP_INLINE_VISIBILITY
77         explicit discard_block_engine(_Sseq& __q,
78         typename enable_if<__is_seed_sequence<_Sseq, discard_block_engine>::value &&
79                            !is_convertible<_Sseq, _Engine>::value>::type* = 0)
80         : __e_(__q), __n_(0) {}
81     _LIBCPP_INLINE_VISIBILITY
82     void seed() {__e_.seed(); __n_ = 0;}
83     _LIBCPP_INLINE_VISIBILITY
84     void seed(result_type __sd) {__e_.seed(__sd); __n_ = 0;}
85     template<class _Sseq>
86         _LIBCPP_INLINE_VISIBILITY
87         typename enable_if
88         <
89             __is_seed_sequence<_Sseq, discard_block_engine>::value,
90             void
91         >::type
92         seed(_Sseq& __q) {__e_.seed(__q); __n_ = 0;}
93 
94     // generating functions
95     _LIBCPP_HIDE_FROM_ABI result_type operator()();
96     _LIBCPP_INLINE_VISIBILITY
97     void discard(unsigned long long __z) {for (; __z; --__z) operator()();}
98 
99     // property functions
100     _LIBCPP_INLINE_VISIBILITY
101     const _Engine& base() const _NOEXCEPT {return __e_;}
102 
103     template<class _Eng, size_t _Pp, size_t _Rp>
104     friend
105     bool
106     operator==(
107         const discard_block_engine<_Eng, _Pp, _Rp>& __x,
108         const discard_block_engine<_Eng, _Pp, _Rp>& __y);
109 
110     template<class _Eng, size_t _Pp, size_t _Rp>
111     friend
112     bool
113     operator!=(
114         const discard_block_engine<_Eng, _Pp, _Rp>& __x,
115         const discard_block_engine<_Eng, _Pp, _Rp>& __y);
116 
117     template <class _CharT, class _Traits,
118               class _Eng, size_t _Pp, size_t _Rp>
119     friend
120     basic_ostream<_CharT, _Traits>&
121     operator<<(basic_ostream<_CharT, _Traits>& __os,
122                const discard_block_engine<_Eng, _Pp, _Rp>& __x);
123 
124     template <class _CharT, class _Traits,
125               class _Eng, size_t _Pp, size_t _Rp>
126     friend
127     basic_istream<_CharT, _Traits>&
128     operator>>(basic_istream<_CharT, _Traits>& __is,
129                discard_block_engine<_Eng, _Pp, _Rp>& __x);
130 };
131 
132 template<class _Engine, size_t __p, size_t __r>
133     _LIBCPP_CONSTEXPR const size_t discard_block_engine<_Engine, __p, __r>::block_size;
134 
135 template<class _Engine, size_t __p, size_t __r>
136     _LIBCPP_CONSTEXPR const size_t discard_block_engine<_Engine, __p, __r>::used_block;
137 
138 template<class _Engine, size_t __p, size_t __r>
139 typename discard_block_engine<_Engine, __p, __r>::result_type
140 discard_block_engine<_Engine, __p, __r>::operator()()
141 {
142     if (__n_ >= static_cast<int>(__r))
143     {
144         __e_.discard(__p - __r);
145         __n_ = 0;
146     }
147     ++__n_;
148     return __e_();
149 }
150 
151 template<class _Eng, size_t _Pp, size_t _Rp>
152 inline _LIBCPP_INLINE_VISIBILITY
153 bool
154 operator==(const discard_block_engine<_Eng, _Pp, _Rp>& __x,
155            const discard_block_engine<_Eng, _Pp, _Rp>& __y)
156 {
157     return __x.__n_ == __y.__n_ && __x.__e_ == __y.__e_;
158 }
159 
160 template<class _Eng, size_t _Pp, size_t _Rp>
161 inline _LIBCPP_INLINE_VISIBILITY
162 bool
163 operator!=(const discard_block_engine<_Eng, _Pp, _Rp>& __x,
164            const discard_block_engine<_Eng, _Pp, _Rp>& __y)
165 {
166     return !(__x == __y);
167 }
168 
169 template <class _CharT, class _Traits,
170           class _Eng, size_t _Pp, size_t _Rp>
171 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
172 operator<<(basic_ostream<_CharT, _Traits>& __os,
173            const discard_block_engine<_Eng, _Pp, _Rp>& __x)
174 {
175     __save_flags<_CharT, _Traits> __lx(__os);
176     typedef basic_ostream<_CharT, _Traits> _Ostream;
177     __os.flags(_Ostream::dec | _Ostream::left);
178     _CharT __sp = __os.widen(' ');
179     __os.fill(__sp);
180     return __os << __x.__e_ << __sp << __x.__n_;
181 }
182 
183 template <class _CharT, class _Traits,
184           class _Eng, size_t _Pp, size_t _Rp>
185 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
186 operator>>(basic_istream<_CharT, _Traits>& __is,
187            discard_block_engine<_Eng, _Pp, _Rp>& __x)
188 {
189     __save_flags<_CharT, _Traits> __lx(__is);
190     typedef basic_istream<_CharT, _Traits> _Istream;
191     __is.flags(_Istream::dec | _Istream::skipws);
192     _Eng __e;
193     int __n;
194     __is >> __e >> __n;
195     if (!__is.fail())
196     {
197         __x.__e_ = __e;
198         __x.__n_ = __n;
199     }
200     return __is;
201 }
202 
203 _LIBCPP_END_NAMESPACE_STD
204 
205 _LIBCPP_POP_MACROS
206 
207 #endif // _LIBCPP___RANDOM_DISCARD_BLOCK_ENGINE_H
208