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 <__utility/move.h>
15 #include <iosfwd>
16 #include <limits>
17 #include <type_traits>
18 
19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20 #  pragma GCC system_header
21 #endif
22 
23 _LIBCPP_PUSH_MACROS
24 #include <__undef_macros>
25 
26 _LIBCPP_BEGIN_NAMESPACE_STD
27 
28 template<class _Engine, size_t __p, size_t __r>
29 class _LIBCPP_TEMPLATE_VIS discard_block_engine
30 {
31     _Engine __e_;
32     int     __n_;
33 
34     static_assert(  0 <  __r, "discard_block_engine invalid parameters");
35     static_assert(__r <= __p, "discard_block_engine invalid parameters");
36 #ifndef _LIBCPP_CXX03_LANG // numeric_limits::max() is not constexpr in C++03
37     static_assert(__r <= numeric_limits<int>::max(), "discard_block_engine invalid parameters");
38 #endif
39 public:
40     // types
41     typedef typename _Engine::result_type result_type;
42 
43     // engine characteristics
44     static _LIBCPP_CONSTEXPR const size_t block_size = __p;
45     static _LIBCPP_CONSTEXPR const size_t used_block = __r;
46 
47 #ifdef _LIBCPP_CXX03_LANG
48     static const result_type _Min = _Engine::_Min;
49     static const result_type _Max = _Engine::_Max;
50 #else
51     static _LIBCPP_CONSTEXPR const result_type _Min = _Engine::min();
52     static _LIBCPP_CONSTEXPR const result_type _Max = _Engine::max();
53 #endif
54 
55     _LIBCPP_INLINE_VISIBILITY
56     static _LIBCPP_CONSTEXPR result_type min() { return _Engine::min(); }
57     _LIBCPP_INLINE_VISIBILITY
58     static _LIBCPP_CONSTEXPR result_type max() { return _Engine::max(); }
59 
60     // constructors and seeding functions
61     _LIBCPP_INLINE_VISIBILITY
62     discard_block_engine() : __n_(0) {}
63     _LIBCPP_INLINE_VISIBILITY
64     explicit discard_block_engine(const _Engine& __e)
65         : __e_(__e), __n_(0) {}
66 #ifndef _LIBCPP_CXX03_LANG
67     _LIBCPP_INLINE_VISIBILITY
68     explicit discard_block_engine(_Engine&& __e)
69         : __e_(_VSTD::move(__e)), __n_(0) {}
70 #endif // _LIBCPP_CXX03_LANG
71     _LIBCPP_INLINE_VISIBILITY
72     explicit discard_block_engine(result_type __sd) : __e_(__sd), __n_(0) {}
73     template<class _Sseq>
74         _LIBCPP_INLINE_VISIBILITY
75         explicit discard_block_engine(_Sseq& __q,
76         typename enable_if<__is_seed_sequence<_Sseq, discard_block_engine>::value &&
77                            !is_convertible<_Sseq, _Engine>::value>::type* = 0)
78         : __e_(__q), __n_(0) {}
79     _LIBCPP_INLINE_VISIBILITY
80     void seed() {__e_.seed(); __n_ = 0;}
81     _LIBCPP_INLINE_VISIBILITY
82     void seed(result_type __sd) {__e_.seed(__sd); __n_ = 0;}
83     template<class _Sseq>
84         _LIBCPP_INLINE_VISIBILITY
85         typename enable_if
86         <
87             __is_seed_sequence<_Sseq, discard_block_engine>::value,
88             void
89         >::type
90         seed(_Sseq& __q) {__e_.seed(__q); __n_ = 0;}
91 
92     // generating functions
93     result_type operator()();
94     _LIBCPP_INLINE_VISIBILITY
95     void discard(unsigned long long __z) {for (; __z; --__z) operator()();}
96 
97     // property functions
98     _LIBCPP_INLINE_VISIBILITY
99     const _Engine& base() const _NOEXCEPT {return __e_;}
100 
101     template<class _Eng, size_t _Pp, size_t _Rp>
102     friend
103     bool
104     operator==(
105         const discard_block_engine<_Eng, _Pp, _Rp>& __x,
106         const discard_block_engine<_Eng, _Pp, _Rp>& __y);
107 
108     template<class _Eng, size_t _Pp, size_t _Rp>
109     friend
110     bool
111     operator!=(
112         const discard_block_engine<_Eng, _Pp, _Rp>& __x,
113         const discard_block_engine<_Eng, _Pp, _Rp>& __y);
114 
115     template <class _CharT, class _Traits,
116               class _Eng, size_t _Pp, size_t _Rp>
117     friend
118     basic_ostream<_CharT, _Traits>&
119     operator<<(basic_ostream<_CharT, _Traits>& __os,
120                const discard_block_engine<_Eng, _Pp, _Rp>& __x);
121 
122     template <class _CharT, class _Traits,
123               class _Eng, size_t _Pp, size_t _Rp>
124     friend
125     basic_istream<_CharT, _Traits>&
126     operator>>(basic_istream<_CharT, _Traits>& __is,
127                discard_block_engine<_Eng, _Pp, _Rp>& __x);
128 };
129 
130 template<class _Engine, size_t __p, size_t __r>
131     _LIBCPP_CONSTEXPR const size_t discard_block_engine<_Engine, __p, __r>::block_size;
132 
133 template<class _Engine, size_t __p, size_t __r>
134     _LIBCPP_CONSTEXPR const size_t discard_block_engine<_Engine, __p, __r>::used_block;
135 
136 template<class _Engine, size_t __p, size_t __r>
137 typename discard_block_engine<_Engine, __p, __r>::result_type
138 discard_block_engine<_Engine, __p, __r>::operator()()
139 {
140     if (__n_ >= static_cast<int>(__r))
141     {
142         __e_.discard(__p - __r);
143         __n_ = 0;
144     }
145     ++__n_;
146     return __e_();
147 }
148 
149 template<class _Eng, size_t _Pp, size_t _Rp>
150 inline _LIBCPP_INLINE_VISIBILITY
151 bool
152 operator==(const discard_block_engine<_Eng, _Pp, _Rp>& __x,
153            const discard_block_engine<_Eng, _Pp, _Rp>& __y)
154 {
155     return __x.__n_ == __y.__n_ && __x.__e_ == __y.__e_;
156 }
157 
158 template<class _Eng, size_t _Pp, size_t _Rp>
159 inline _LIBCPP_INLINE_VISIBILITY
160 bool
161 operator!=(const discard_block_engine<_Eng, _Pp, _Rp>& __x,
162            const discard_block_engine<_Eng, _Pp, _Rp>& __y)
163 {
164     return !(__x == __y);
165 }
166 
167 template <class _CharT, class _Traits,
168           class _Eng, size_t _Pp, size_t _Rp>
169 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
170 operator<<(basic_ostream<_CharT, _Traits>& __os,
171            const discard_block_engine<_Eng, _Pp, _Rp>& __x)
172 {
173     __save_flags<_CharT, _Traits> __lx(__os);
174     typedef basic_ostream<_CharT, _Traits> _Ostream;
175     __os.flags(_Ostream::dec | _Ostream::left);
176     _CharT __sp = __os.widen(' ');
177     __os.fill(__sp);
178     return __os << __x.__e_ << __sp << __x.__n_;
179 }
180 
181 template <class _CharT, class _Traits,
182           class _Eng, size_t _Pp, size_t _Rp>
183 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
184 operator>>(basic_istream<_CharT, _Traits>& __is,
185            discard_block_engine<_Eng, _Pp, _Rp>& __x)
186 {
187     __save_flags<_CharT, _Traits> __lx(__is);
188     typedef basic_istream<_CharT, _Traits> _Istream;
189     __is.flags(_Istream::dec | _Istream::skipws);
190     _Eng __e;
191     int __n;
192     __is >> __e >> __n;
193     if (!__is.fail())
194     {
195         __x.__e_ = __e;
196         __x.__n_ = __n;
197     }
198     return __is;
199 }
200 
201 _LIBCPP_END_NAMESPACE_STD
202 
203 _LIBCPP_POP_MACROS
204 
205 #endif // _LIBCPP___RANDOM_DISCARD_BLOCK_ENGINE_H
206