. /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/buffers/buffer_slice.hpp> 16   #include <boost/capy/buffers/buffer_slice.hpp>
17   #include <coroutine> 17   #include <coroutine>
18   #include <boost/capy/ex/io_env.hpp> 18   #include <boost/capy/ex/io_env.hpp>
19   19  
20   #include <algorithm> 20   #include <algorithm>
21   #include <cstddef> 21   #include <cstddef>
22   #include <type_traits> 22   #include <type_traits>
23   #include <utility> 23   #include <utility>
24   24  
25   namespace boost { 25   namespace boost {
26   namespace capy { 26   namespace capy {
27   namespace test { 27   namespace test {
28   28  
29   /** Iterates split points of a buffer sequence into two adjacent halves. 29   /** Iterates split points of a buffer sequence into two adjacent halves.
30   30  
31   This class iterates through all possible ways to split a buffer 31   This class iterates through all possible ways to split a buffer
32   sequence into two parts (b1, b2) where concatenating them yields 32   sequence into two parts (b1, b2) where concatenating them yields
33   the original sequence. It uses an async-generator-like pattern 33   the original sequence. It uses an async-generator-like pattern
34   that allows `co_await` between iterations. 34   that allows `co_await` between iterations.
35   35  
36   The split type automatically preserves mutability: passing a 36   The split type automatically preserves mutability: passing a
37   `MutableBufferSequence` yields halves that model 37   `MutableBufferSequence` yields halves that model
38   @ref MutableBufferSequence, while passing a `ConstBufferSequence` 38   @ref MutableBufferSequence, while passing a `ConstBufferSequence`
39   yields halves that model @ref ConstBufferSequence. Each half is 39   yields halves that model @ref ConstBufferSequence. Each half is
40   the buffer-sequence view exposed by a @ref buffer_slice over the 40   the buffer-sequence view exposed by a @ref buffer_slice over the
41   corresponding byte range, and can be passed directly to 41   corresponding byte range, and can be passed directly to
42   `read_some`, `write_some`, `buffer_size`, etc. 42   `read_some`, `write_some`, `buffer_size`, etc.
43   43  
44   @par Thread Safety 44   @par Thread Safety
45   Not thread-safe. 45   Not thread-safe.
46   46  
47   @par Example 47   @par Example
48   @par !example example_1 48   @par !example example_1
49   49  
50   50  
51   @par Mutable Buffer Example 51   @par Mutable Buffer Example
52   @par !example example_2 52   @par !example example_2
53   53  
54   54  
55   @par Step Size Example 55   @par Step Size Example
56   @par !example example_3 56   @par !example example_3
57   57  
58   58  
59   @see buffer_slice 59   @see buffer_slice
60   */ 60   */
61   template<ConstBufferSequence BS> 61   template<ConstBufferSequence BS>
62   class bufgrind 62   class bufgrind
63   { 63   {
64   BS const& bs_; 64   BS const& bs_;
65   std::size_t size_; 65   std::size_t size_;
66   std::size_t step_; 66   std::size_t step_;
67   std::size_t pos_ = 0; 67   std::size_t pos_ = 0;
68   68  
69   public: 69   public:
70   /// Names the buffer-sequence type `buffer_slice` yields for each half. 70   /// Names the buffer-sequence type `buffer_slice` yields for each half.
71   using slice_type = std::decay_t< 71   using slice_type = std::decay_t<
72   decltype(buffer_slice(std::declval<BS const&>()))>; 72   decltype(buffer_slice(std::declval<BS const&>()))>;
73   73  
74   /// Pairs the two `slice_type` halves that @ref next yields together. 74   /// Pairs the two `slice_type` halves that @ref next yields together.
75   using split_type = std::pair<slice_type, slice_type>; 75   using split_type = std::pair<slice_type, slice_type>;
76   76  
77   /** Construct a buffer grinder. 77   /** Construct a buffer grinder.
78   78  
79   @param bs The buffer sequence to iterate over. 79   @param bs The buffer sequence to iterate over.
80   80  
81   @param step The number of bytes to advance on each call to 81   @param step The number of bytes to advance on each call to
82   @ref next. A value of 0 is treated as 1. The final split 82   @ref next. A value of 0 is treated as 1. The final split
83   at `buffer_size( bs )` is always included regardless of 83   at `buffer_size( bs )` is always included regardless of
84   step alignment. 84   step alignment.
85   */ 85   */
86   explicit 86   explicit
HITCBC 87   39 bufgrind( 87   39 bufgrind(
88   BS const& bs, 88   BS const& bs,
89   std::size_t step = 1) noexcept 89   std::size_t step = 1) noexcept
HITCBC 90   39 : bs_(bs) 90   39 : bs_(bs)
HITCBC 91   39 , size_(buffer_size(bs)) 91   39 , size_(buffer_size(bs))
HITCBC 92   39 , step_(step > 0 ? step : 1) 92   39 , step_(step > 0 ? step : 1)
93   { 93   {
HITCBC 94   39 } 94   39 }
95   95  
96   /** Check if more split points remain. 96   /** Check if more split points remain.
97   97  
98   @return `true` if @ref next can be called, `false` otherwise. 98   @return `true` if @ref next can be called, `false` otherwise.
99   */ 99   */
HITCBC 100   237 explicit operator bool() const noexcept 100   237 explicit operator bool() const noexcept
101   { 101   {
HITCBC 102   237 return pos_ <= size_; 102   237 return pos_ <= size_;
103   } 103   }
104   104  
105   /** Computes the current split synchronously, so awaiting it never suspends the caller. 105   /** Computes the current split synchronously, so awaiting it never suspends the caller.
106   */ 106   */
107   struct next_awaitable 107   struct next_awaitable
108   { 108   {
109   /// The grinder that produced this awaitable. 109   /// The grinder that produced this awaitable.
110   bufgrind* self_; 110   bufgrind* self_;
111   111  
112   /** Report whether the awaitable is ready. 112   /** Report whether the awaitable is ready.
113   113  
114   @return `true` always; the split is available without suspending. 114   @return `true` always; the split is available without suspending.
115   */ 115   */
HITCBC 116   198 bool await_ready() const noexcept { return true; } 116   198 bool await_ready() const noexcept { return true; }
117   117  
118   /** Resume the caller inline without suspending. 118   /** Resume the caller inline without suspending.
119   119  
120   @param h The awaiting coroutine handle. 120   @param h The awaiting coroutine handle.
121   121  
122   @return @p h, so the caller resumes immediately. 122   @return @p h, so the caller resumes immediately.
123   */ 123   */
MISUBC 124   ✗ std::coroutine_handle<> await_suspend(std::coroutine_handle<> h, io_env const*) const noexcept { return h; } 124   ✗ std::coroutine_handle<> await_suspend(std::coroutine_handle<> h, io_env const*) const noexcept { return h; }
125   125  
126   /** Return the current split and advance to the next. 126   /** Return the current split and advance to the next.
127   127  
128   @return The `(b1, b2)` split at the current position. 128   @return The `(b1, b2)` split at the current position.
129   */ 129   */
130   split_type 130   split_type
HITCBC 131   198 await_resume() 131   198 await_resume()
132   { 132   {
HITCBC 133   198 split_type result{ 133   198 split_type result{
HITCBC 134   198 buffer_slice(self_->bs_, 0, self_->pos_), 134   198 buffer_slice(self_->bs_, 0, self_->pos_),
HITCBC 135   198 buffer_slice(self_->bs_, self_->pos_) 135   198 buffer_slice(self_->bs_, self_->pos_)
136   }; 136   };
HITCBC 137   198 if(self_->pos_ < self_->size_) 137   198 if(self_->pos_ < self_->size_)
HITCBC 138   161 self_->pos_ = (std::min)(self_->pos_ + self_->step_, self_->size_); 138   161 self_->pos_ = (std::min)(self_->pos_ + self_->step_, self_->size_);
139   else 139   else
HITCBC 140   37 ++self_->pos_; 140   37 ++self_->pos_;
HITCBC 141   198 return result; 141   198 return result;
142   } 142   }
143   }; 143   };
144   144  
145   /** Return the next split point. 145   /** Return the next split point.
146   146  
147   Returns an awaitable that yields the current (b1, b2) pair 147   Returns an awaitable that yields the current (b1, b2) pair
148   and advances to the next split point. 148   and advances to the next split point.
149   149  
150   @par Preconditions 150   @par Preconditions
151   `static_cast<bool>( *this )` is `true`. 151   `static_cast<bool>( *this )` is `true`.
152   152  
153   @return An awaitable that await-returns `split_type`. 153   @return An awaitable that await-returns `split_type`.
154   */ 154   */
155   next_awaitable 155   next_awaitable
HITCBC 156   198 next() noexcept 156   198 next() noexcept
157   { 157   {
HITCBC 158   198 return {this}; 158   198 return {this};
159   } 159   }
160   }; 160   };
161   161  
162   } // test 162   } // test
163   } // capy 163   } // capy
164   } // boost 164   } // boost
165   165  
166   #endif 166   #endif