. /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   // 4   //
4   // Distributed under the Boost Software License, Version 1.0. (See accompanying 5   // Distributed under the Boost Software License, Version 1.0. (See accompanying
5   // 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)
6   // 7   //
7   // Official repository: https://github.com/cppalliance/capy 8   // Official repository: https://github.com/cppalliance/capy
8   // 9   //
9   10  
10   #ifndef BOOST_CAPY_TEST_BUFGRIND_HPP 11   #ifndef BOOST_CAPY_TEST_BUFGRIND_HPP
11   #define BOOST_CAPY_TEST_BUFGRIND_HPP 12   #define BOOST_CAPY_TEST_BUFGRIND_HPP
12   13  
13   #include <boost/capy/detail/config.hpp> 14   #include <boost/capy/detail/config.hpp>
14   #include <boost/capy/buffers.hpp> 15   #include <boost/capy/buffers.hpp>
15   #include <boost/capy/buffers/buffer_slice.hpp> 16   #include <boost/capy/buffers/buffer_slice.hpp>
16   #include <coroutine> 17   #include <coroutine>
17   #include <boost/capy/ex/io_env.hpp> 18   #include <boost/capy/ex/io_env.hpp>
18   19  
19   #include <algorithm> 20   #include <algorithm>
20   #include <cstddef> 21   #include <cstddef>
21   #include <type_traits> 22   #include <type_traits>
22   #include <utility> 23   #include <utility>
23   24  
24   namespace boost { 25   namespace boost {
25   namespace capy { 26   namespace capy {
26   namespace test { 27   namespace test {
27   28  
28 - /** A test utility for iterating buffer sequence split points. 29 + /** Iterates split points of a buffer sequence into two adjacent halves.
29   30  
30   This class iterates through all possible ways to split a buffer 31   This class iterates through all possible ways to split a buffer
31   sequence into two parts (b1, b2) where concatenating them yields 32   sequence into two parts (b1, b2) where concatenating them yields
32   the original sequence. It uses an async-generator-like pattern 33   the original sequence. It uses an async-generator-like pattern
33   that allows `co_await` between iterations. 34   that allows `co_await` between iterations.
34   35  
35   The split type automatically preserves mutability: passing a 36   The split type automatically preserves mutability: passing a
36   `MutableBufferSequence` yields halves that model 37   `MutableBufferSequence` yields halves that model
37   @ref MutableBufferSequence, while passing a `ConstBufferSequence` 38   @ref MutableBufferSequence, while passing a `ConstBufferSequence`
38   yields halves that model @ref ConstBufferSequence. Each half is 39   yields halves that model @ref ConstBufferSequence. Each half is
39   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
40   corresponding byte range, and can be passed directly to 41   corresponding byte range, and can be passed directly to
41   `read_some`, `write_some`, `buffer_size`, etc. 42   `read_some`, `write_some`, `buffer_size`, etc.
42   43  
43   @par Thread Safety 44   @par Thread Safety
44   Not thread-safe. 45   Not thread-safe.
45   46  
46   @par Example 47   @par Example
47   @code 48   @code
48   // Test all split points of a buffer 49   // Test all split points of a buffer
49   std::string data = "hello world"; 50   std::string data = "hello world";
50   auto cb = make_buffer( data ); 51   auto cb = make_buffer( data );
51   52  
52   fuse f; 53   fuse f;
53   auto r = f.inert( [&]( fuse& ) -> task<> { 54   auto r = f.inert( [&]( fuse& ) -> task<> {
54   bufgrind bg( cb ); 55   bufgrind bg( cb );
55   while( bg ) { 56   while( bg ) {
56   auto [b1, b2] = co_await bg.next(); 57   auto [b1, b2] = co_await bg.next();
57   // b1 contains first N bytes (as a buffer sequence) 58   // b1 contains first N bytes (as a buffer sequence)
58   // b2 contains remaining bytes (as a buffer sequence) 59   // b2 contains remaining bytes (as a buffer sequence)
59   // concatenating b1 + b2 equals original 60   // concatenating b1 + b2 equals original
60   co_await some_async_operation( b1, b2 ); 61   co_await some_async_operation( b1, b2 );
61   } 62   }
62   } ); 63   } );
63   @endcode 64   @endcode
64   65  
65   @par Mutable Buffer Example 66   @par Mutable Buffer Example
66   @code 67   @code
67   // Mutable buffers preserve mutability 68   // Mutable buffers preserve mutability
68   char data[100]; 69   char data[100];
69   mutable_buffer mb( data, sizeof( data ) ); 70   mutable_buffer mb( data, sizeof( data ) );
70   71  
71   bufgrind bg( mb ); 72   bufgrind bg( mb );
72   while( bg ) { 73   while( bg ) {
73   auto [b1, b2] = co_await bg.next(); 74   auto [b1, b2] = co_await bg.next();
74   // b1, b2 yield mutable_buffer when iterated 75   // b1, b2 yield mutable_buffer when iterated
75   } 76   }
76   @endcode 77   @endcode
77   78  
78   @par Step Size Example 79   @par Step Size Example
79   @code 80   @code
80   // Skip by 10 bytes for faster iteration 81   // Skip by 10 bytes for faster iteration
81   bufgrind bg( cb, 10 ); 82   bufgrind bg( cb, 10 );
82   while( bg ) { 83   while( bg ) {
83   auto [b1, b2] = co_await bg.next(); 84   auto [b1, b2] = co_await bg.next();
84   // Visits positions 0, 10, 20, ..., and always size 85   // Visits positions 0, 10, 20, ..., and always size
85   } 86   }
86   @endcode 87   @endcode
87   88  
88   @see buffer_slice 89   @see buffer_slice
89   */ 90   */
90   template<ConstBufferSequence BS> 91   template<ConstBufferSequence BS>
91   class bufgrind 92   class bufgrind
92   { 93   {
93   BS const& bs_; 94   BS const& bs_;
94   std::size_t size_; 95   std::size_t size_;
95   std::size_t step_; 96   std::size_t step_;
96   std::size_t pos_ = 0; 97   std::size_t pos_ = 0;
97   98  
98   public: 99   public:
99 - /// The buffer-sequence type produced for each half of a split. 100 + /// Names the buffer-sequence type `buffer_slice` yields for each half.
100   using slice_type = std::decay_t< 101   using slice_type = std::decay_t<
101   decltype(buffer_slice(std::declval<BS const&>()))>; 102   decltype(buffer_slice(std::declval<BS const&>()))>;
102   103  
103 - /// The type returned by @ref next. Each half is itself a buffer 104 + /// Pairs the two `slice_type` halves that @ref next yields together.
104 - /// sequence (the value returned by `buffer_slice`).  
105   using split_type = std::pair<slice_type, slice_type>; 105   using split_type = std::pair<slice_type, slice_type>;
106   106  
107   /** Construct a buffer grinder. 107   /** Construct a buffer grinder.
108   108  
109   @param bs The buffer sequence to iterate over. 109   @param bs The buffer sequence to iterate over.
110   110  
111   @param step The number of bytes to advance on each call to 111   @param step The number of bytes to advance on each call to
112   @ref next. A value of 0 is treated as 1. The final split 112   @ref next. A value of 0 is treated as 1. The final split
113   at `buffer_size( bs )` is always included regardless of 113   at `buffer_size( bs )` is always included regardless of
114   step alignment. 114   step alignment.
115   */ 115   */
116   explicit 116   explicit
HITCBC 117   39 bufgrind( 117   39 bufgrind(
118   BS const& bs, 118   BS const& bs,
119   std::size_t step = 1) noexcept 119   std::size_t step = 1) noexcept
HITCBC 120   39 : bs_(bs) 120   39 : bs_(bs)
HITCBC 121   39 , size_(buffer_size(bs)) 121   39 , size_(buffer_size(bs))
HITCBC 122   39 , step_(step > 0 ? step : 1) 122   39 , step_(step > 0 ? step : 1)
123   { 123   {
HITCBC 124   39 } 124   39 }
125   125  
126   /** Check if more split points remain. 126   /** Check if more split points remain.
127   127  
128   @return `true` if @ref next can be called, `false` otherwise. 128   @return `true` if @ref next can be called, `false` otherwise.
129   */ 129   */
HITCBC 130   237 explicit operator bool() const noexcept 130   237 explicit operator bool() const noexcept
131   { 131   {
HITCBC 132   237 return pos_ <= size_; 132   237 return pos_ <= size_;
133   } 133   }
134   134  
135 - /** Awaitable returned by @ref next. 135 + /** Computes the current split synchronously, so awaiting it never suspends the caller.
136   */ 136   */
137   struct next_awaitable 137   struct next_awaitable
138   { 138   {
  139 + /// The grinder that produced this awaitable.
139   bufgrind* self_; 140   bufgrind* self_;
140   141  
  142 + /** Report whether the awaitable is ready.
  143 +
  144 + @return `true` always; the split is available without suspending.
  145 + */
HITCBC 141   198 bool await_ready() const noexcept { return true; } 146   198 bool await_ready() const noexcept { return true; }
  147 +
  148 + /** Resume the caller inline without suspending.
  149 +
  150 + @param h The awaiting coroutine handle.
  151 +
  152 + @return @p h, so the caller resumes immediately.
  153 + */
MISUBC 142   ✗ std::coroutine_handle<> await_suspend(std::coroutine_handle<> h, io_env const*) const noexcept { return h; } 154   ✗ std::coroutine_handle<> await_suspend(std::coroutine_handle<> h, io_env const*) const noexcept { return h; }
143   155  
  156 + /** Return the current split and advance to the next.
  157 +
  158 + @return The `(b1, b2)` split at the current position.
  159 + */
144   split_type 160   split_type
HITCBC 145   198 await_resume() 161   198 await_resume()
146   { 162   {
HITCBC 147   198 split_type result{ 163   198 split_type result{
HITCBC 148   198 buffer_slice(self_->bs_, 0, self_->pos_), 164   198 buffer_slice(self_->bs_, 0, self_->pos_),
HITCBC 149   198 buffer_slice(self_->bs_, self_->pos_) 165   198 buffer_slice(self_->bs_, self_->pos_)
150   }; 166   };
HITCBC 151   198 if(self_->pos_ < self_->size_) 167   198 if(self_->pos_ < self_->size_)
HITCBC 152   161 self_->pos_ = (std::min)(self_->pos_ + self_->step_, self_->size_); 168   161 self_->pos_ = (std::min)(self_->pos_ + self_->step_, self_->size_);
153   else 169   else
HITCBC 154   37 ++self_->pos_; 170   37 ++self_->pos_;
HITCBC 155   198 return result; 171   198 return result;
156   } 172   }
157   }; 173   };
158   174  
159   /** Return the next split point. 175   /** Return the next split point.
160   176  
161   Returns an awaitable that yields the current (b1, b2) pair 177   Returns an awaitable that yields the current (b1, b2) pair
162   and advances to the next split point. 178   and advances to the next split point.
163   179  
164   @par Preconditions 180   @par Preconditions
165   `static_cast<bool>( *this )` is `true`. 181   `static_cast<bool>( *this )` is `true`.
166   182  
167   @return An awaitable that await-returns `split_type`. 183   @return An awaitable that await-returns `split_type`.
168   */ 184   */
169   next_awaitable 185   next_awaitable
HITCBC 170   198 next() noexcept 186   198 next() noexcept
171   { 187   {
HITCBC 172   198 return {this}; 188   198 return {this};
173   } 189   }
174   }; 190   };
175   191  
176   } // test 192   } // test
177   } // capy 193   } // capy
178   } // boost 194   } // boost
179   195  
180   #endif 196   #endif