. /include/boost/capy /test /bufgrind.hpp
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1   // 1   //
2   // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com) 2   // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3   // Copyright (c) 2026 Michael Vandeberg 3   // Copyright (c) 2026 Michael Vandeberg
4   // 4   //
5   // Distributed under the Boost Software License, Version 1.0. (See accompanying 5   // Distributed under the Boost Software License, Version 1.0. (See accompanying
6   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 6   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7   // 7   //
8   // Official repository: https://github.com/cppalliance/capy 8   // Official repository: https://github.com/cppalliance/capy
9   // 9   //
10   10  
11   #ifndef BOOST_CAPY_TEST_BUFGRIND_HPP 11   #ifndef BOOST_CAPY_TEST_BUFGRIND_HPP
12   #define BOOST_CAPY_TEST_BUFGRIND_HPP 12   #define BOOST_CAPY_TEST_BUFGRIND_HPP
13   13  
14   #include <boost/capy/detail/config.hpp> 14   #include <boost/capy/detail/config.hpp>
15   #include <boost/capy/buffers.hpp> 15   #include <boost/capy/buffers.hpp>
16   #include <boost/capy/detail/slice_of.hpp> 16   #include <boost/capy/detail/slice_of.hpp>
17   #include <coroutine> 17   #include <coroutine>
18   #include <boost/capy/ex/await_context.hpp> 18   #include <boost/capy/ex/await_context.hpp>
19   19  
20   #include <algorithm> 20   #include <algorithm>
21   #include <cstddef> 21   #include <cstddef>
22   #include <limits> 22   #include <limits>
23   #include <type_traits> 23   #include <type_traits>
24   #include <utility> 24   #include <utility>
25   25  
26   namespace boost { 26   namespace boost {
27   namespace capy { 27   namespace capy {
28   namespace test { 28   namespace test {
29   29  
30   /** Iterates split points of a buffer sequence into two adjacent halves. 30   /** Iterates split points of a buffer sequence into two adjacent halves.
31   31  
32   This class iterates through all possible ways to split a buffer 32   This class iterates through all possible ways to split a buffer
33   sequence into two parts (b1, b2) where concatenating them yields 33   sequence into two parts (b1, b2) where concatenating them yields
34   the original sequence. It uses an async-generator-like pattern 34   the original sequence. It uses an async-generator-like pattern
35   that allows `co_await` between iterations. 35   that allows `co_await` between iterations.
36   36  
37   The split type automatically preserves mutability: passing a 37   The split type automatically preserves mutability: passing a
38   `MutableBufferSequence` yields halves that model 38   `MutableBufferSequence` yields halves that model
39   @ref MutableBufferSequence, while passing a `ConstBufferSequence` 39   @ref MutableBufferSequence, while passing a `ConstBufferSequence`
40   yields halves that model @ref ConstBufferSequence. A single buffer 40   yields halves that model @ref ConstBufferSequence. A single buffer
41   splits into two `mutable_buffer` or `const_buffer` values; any other 41   splits into two `mutable_buffer` or `const_buffer` values; any other
42   sequence splits into two borrowed views. Either way each half can be 42   sequence splits into two borrowed views. Either way each half can be
43   passed directly to `read_some`, `write_some`, `buffer_size`, etc. 43   passed directly to `read_some`, `write_some`, `buffer_size`, etc.
44   44  
45   @par Thread Safety 45   @par Thread Safety
46   Not thread-safe. 46   Not thread-safe.
47   47  
48   @par Example 48   @par Example
49   @par !example example_1 49   @par !example example_1
50   50  
51   51  
52   @par Mutable Buffer Example 52   @par Mutable Buffer Example
53   @par !example example_2 53   @par !example example_2
54   54  
55   55  
56   @par Step Size Example 56   @par Step Size Example
57   @par !example example_3 57   @par !example example_3
58   58  
59   */ 59   */
60   template<ConstBufferSequence BS> 60   template<ConstBufferSequence BS>
61   class bufgrind 61   class bufgrind
62   { 62   {
63   BS const& bs_; 63   BS const& bs_;
64   std::size_t size_; 64   std::size_t size_;
65   std::size_t step_; 65   std::size_t step_;
66   std::size_t pos_ = 0; 66   std::size_t pos_ = 0;
67   67  
68   public: 68   public:
69   /// Names the buffer-sequence type of each half. 69   /// Names the buffer-sequence type of each half.
70   using slice_type = std::conditional_t< 70   using slice_type = std::conditional_t<
71   ConstBuffer<BS>, 71   ConstBuffer<BS>,
72   buffer_type<BS>, 72   buffer_type<BS>,
73   detail::slice_of<BS>>; 73   detail::slice_of<BS>>;
74   74  
75   /// Pairs the two `slice_type` halves that @ref next yields together. 75   /// Pairs the two `slice_type` halves that @ref next yields together.
76   using split_type = std::pair<slice_type, slice_type>; 76   using split_type = std::pair<slice_type, slice_type>;
77   77  
78   private: 78   private:
79   static slice_type 79   static slice_type
HITCBC 80   396 slice( 80   396 slice(
81   BS const& bs, 81   BS const& bs,
82   std::size_t offset, 82   std::size_t offset,
83   std::size_t length = 83   std::size_t length =
84   (std::numeric_limits<std::size_t>::max)()) noexcept 84   (std::numeric_limits<std::size_t>::max)()) noexcept
85   { 85   {
86   if constexpr (ConstBuffer<BS>) 86   if constexpr (ConstBuffer<BS>)
87   { 87   {
HITCBC 88   382 slice_type b = bs; 88   382 slice_type b = bs;
HITCBC 89   382 b += offset; 89   382 b += offset;
HITCBC 90   382 if(length < b.size()) 90   382 if(length < b.size())
HITCBC 91   155 b = slice_type(b.data(), length); 91   155 b = slice_type(b.data(), length);
HITCBC 92   382 return b; 92   382 return b;
93   } 93   }
94   else 94   else
95   { 95   {
HITCBC 96   14 return slice_type(bs, offset, length); 96   14 return slice_type(bs, offset, length);
97   } 97   }
98   } 98   }
99   99  
100   public: 100   public:
101   101  
102   /** Construct a buffer grinder. 102   /** Construct a buffer grinder.
103   103  
104   @param bs The buffer sequence to iterate over. 104   @param bs The buffer sequence to iterate over.
105   105  
106   @param step The number of bytes to advance on each call to 106   @param step The number of bytes to advance on each call to
107   @ref next. A value of 0 is treated as 1. The final split 107   @ref next. A value of 0 is treated as 1. The final split
108   at `buffer_size( bs )` is always included regardless of 108   at `buffer_size( bs )` is always included regardless of
109   step alignment. 109   step alignment.
110   */ 110   */
111   explicit 111   explicit
HITCBC 112   39 bufgrind( 112   39 bufgrind(
113   BS const& bs, 113   BS const& bs,
114   std::size_t step = 1) noexcept 114   std::size_t step = 1) noexcept
HITCBC 115   39 : bs_(bs) 115   39 : bs_(bs)
HITCBC 116   39 , size_(buffer_size(bs)) 116   39 , size_(buffer_size(bs))
HITCBC 117   39 , step_(step > 0 ? step : 1) 117   39 , step_(step > 0 ? step : 1)
118   { 118   {
HITCBC 119   39 } 119   39 }
120   120  
121   /** Check if more split points remain. 121   /** Check if more split points remain.
122   122  
123   @return `true` if @ref next can be called, `false` otherwise. 123   @return `true` if @ref next can be called, `false` otherwise.
124   */ 124   */
HITCBC 125   237 explicit operator bool() const noexcept 125   237 explicit operator bool() const noexcept
126   { 126   {
HITCBC 127   237 return pos_ <= size_; 127   237 return pos_ <= size_;
128   } 128   }
129   129  
130   /** Computes the current split synchronously, so awaiting it never suspends the caller. 130   /** Computes the current split synchronously, so awaiting it never suspends the caller.
131   */ 131   */
132   struct next_awaitable 132   struct next_awaitable
133   { 133   {
134   /// The grinder that produced this awaitable. 134   /// The grinder that produced this awaitable.
135   bufgrind* self_; 135   bufgrind* self_;
136   136  
137   /** Report whether the awaitable is ready. 137   /** Report whether the awaitable is ready.
138   138  
139   @return `true` always; the split is available without suspending. 139   @return `true` always; the split is available without suspending.
140   */ 140   */
HITCBC 141   198 bool await_ready() const noexcept { return true; } 141   198 bool await_ready() const noexcept { return true; }
142   142  
143   /** Resume the caller inline without suspending. 143   /** Resume the caller inline without suspending.
144   144  
145   @param h The awaiting coroutine handle. 145   @param h The awaiting coroutine handle.
146   146  
147   @return @p h, so the caller resumes immediately. 147   @return @p h, so the caller resumes immediately.
148   */ 148   */
MISUBC 149   ✗ std::coroutine_handle<> await_suspend(std::coroutine_handle<> h, await_context const*) const noexcept { return h; } 149   ✗ std::coroutine_handle<> await_suspend(std::coroutine_handle<> h, await_context const*) const noexcept { return h; }
150   150  
151   /** Return the current split and advance to the next. 151   /** Return the current split and advance to the next.
152   152  
153   @return The `(b1, b2)` split at the current position. 153   @return The `(b1, b2)` split at the current position.
154   */ 154   */
155   split_type 155   split_type
HITCBC 156   198 await_resume() 156   198 await_resume()
157   { 157   {
HITCBC 158   198 split_type result{ 158   198 split_type result{
HITCBC 159   198 slice(self_->bs_, 0, self_->pos_), 159   198 slice(self_->bs_, 0, self_->pos_),
HITCBC 160   198 slice(self_->bs_, self_->pos_) 160   198 slice(self_->bs_, self_->pos_)
161   }; 161   };
HITCBC 162   198 if(self_->pos_ < self_->size_) 162   198 if(self_->pos_ < self_->size_)
HITCBC 163   161 self_->pos_ = (std::min)(self_->pos_ + self_->step_, self_->size_); 163   161 self_->pos_ = (std::min)(self_->pos_ + self_->step_, self_->size_);
164   else 164   else
HITCBC 165   37 ++self_->pos_; 165   37 ++self_->pos_;
HITCBC 166   198 return result; 166   198 return result;
167   } 167   }
168   }; 168   };
169   169  
170   /** Return the next split point. 170   /** Return the next split point.
171   171  
172   Returns an awaitable that yields the current (b1, b2) pair 172   Returns an awaitable that yields the current (b1, b2) pair
173   and advances to the next split point. 173   and advances to the next split point.
174   174  
175   @par Preconditions 175   @par Preconditions
176   `static_cast<bool>( *this )` is `true`. 176   `static_cast<bool>( *this )` is `true`.
177   177  
178   @return An awaitable that await-returns `split_type`. 178   @return An awaitable that await-returns `split_type`.
179   */ 179   */
180   next_awaitable 180   next_awaitable
HITCBC 181   198 next() noexcept 181   198 next() noexcept
182   { 182   {
HITCBC 183   198 return {this}; 183   198 return {this};
184   } 184   }
185   }; 185   };
186   186  
187   } // test 187   } // test
188   } // capy 188   } // capy
189   } // boost 189   } // boost
190   190  
191   #endif 191   #endif