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   _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 
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 
min()57   _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type min() { return _Engine::min(); }
max()58   _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type max() { return _Engine::max(); }
59 
60   // constructors and seeding functions
discard_block_engine()61   _LIBCPP_HIDE_FROM_ABI discard_block_engine() : __n_(0) {}
discard_block_engine(const _Engine & __e)62   _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(const _Engine& __e) : __e_(__e), __n_(0) {}
63 #ifndef _LIBCPP_CXX03_LANG
discard_block_engine(_Engine && __e)64   _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(_Engine&& __e) : __e_(std::move(__e)), __n_(0) {}
65 #endif // _LIBCPP_CXX03_LANG
discard_block_engine(result_type __sd)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>
discard_block_engine(_Sseq & __q)71   _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(_Sseq& __q) : __e_(__q), __n_(0) {}
seed()72   _LIBCPP_HIDE_FROM_ABI void seed() {
73     __e_.seed();
74     __n_ = 0;
75   }
seed(result_type __sd)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>
seed(_Sseq & __q)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()();
discard(unsigned long long __z)88   _LIBCPP_HIDE_FROM_ABI void discard(unsigned long long __z) {
89     for (; __z; --__z)
90       operator()();
91   }
92 
93   // property functions
base()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 
113 template <class _Engine, size_t __p, size_t __r>
114 _LIBCPP_CONSTEXPR const size_t discard_block_engine<_Engine, __p, __r>::block_size;
115 
116 template <class _Engine, size_t __p, size_t __r>
117 _LIBCPP_CONSTEXPR const size_t discard_block_engine<_Engine, __p, __r>::used_block;
118 
119 template <class _Engine, size_t __p, size_t __r>
operator()120 typename 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 
129 template <class _Eng, size_t _Pp, size_t _Rp>
130 inline _LIBCPP_HIDE_FROM_ABI bool
131 operator==(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 
135 template <class _Eng, size_t _Pp, size_t _Rp>
136 inline _LIBCPP_HIDE_FROM_ABI bool
137 operator!=(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y) {
138   return !(__x == __y);
139 }
140 
141 template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
142 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
143 operator<<(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 
152 template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
153 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
154 operator>>(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