. /include/boost/capy /read.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   // 3   //
4   // Distributed under the Boost Software License, Version 1.0. (See accompanying 4   // 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) 5   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6   // 6   //
7   // Official repository: https://github.com/cppalliance/capy 7   // Official repository: https://github.com/cppalliance/capy
8   // 8   //
9   9  
10   #ifndef BOOST_CAPY_READ_HPP 10   #ifndef BOOST_CAPY_READ_HPP
11   #define BOOST_CAPY_READ_HPP 11   #define BOOST_CAPY_READ_HPP
12   12  
13   #include <boost/capy/detail/config.hpp> 13   #include <boost/capy/detail/config.hpp>
14   #include <boost/capy/cond.hpp> 14   #include <boost/capy/cond.hpp>
15   #include <boost/capy/io_task.hpp> 15   #include <boost/capy/io_task.hpp>
16   #include <boost/capy/buffers.hpp> 16   #include <boost/capy/buffers.hpp>
17   #include <boost/capy/buffers/buffer_slice.hpp> 17   #include <boost/capy/buffers/buffer_slice.hpp>
18   #include <boost/capy/concept/dynamic_buffer.hpp> 18   #include <boost/capy/concept/dynamic_buffer.hpp>
19   #include <boost/capy/concept/read_source.hpp> 19   #include <boost/capy/concept/read_source.hpp>
20   #include <boost/capy/concept/read_stream.hpp> 20   #include <boost/capy/concept/read_stream.hpp>
21   #include <system_error> 21   #include <system_error>
22   22  
23   #include <cstddef> 23   #include <cstddef>
24   24  
25   namespace boost { 25   namespace boost {
26   namespace capy { 26   namespace capy {
27   27  
28   /** Read data from a stream until the buffer sequence is full. 28   /** Read data from a stream until the buffer sequence is full.
29   29  
30   @par Await-effects 30   @par Await-effects
31   31  
32   Reads data from `stream` via awaiting `stream.read_some` repeatedly 32   Reads data from `stream` via awaiting `stream.read_some` repeatedly
33   until: 33   until:
34   34  
35   @li either the entire buffer sequence @c buffers is filled, 35   @li either the entire buffer sequence @c buffers is filled,
36 - @li or a contingency occurs on `stream.read_some`. 36 + @li or a contingency occurs.
37   37  
38   If `buffer_size(buffers) == 0` then no awaiting `stream.read_some` 38   If `buffer_size(buffers) == 0` then no awaiting `stream.read_some`
39   is performed. This is not a contingency. 39   is performed. This is not a contingency.
40   40  
41   @par Await-returns 41   @par Await-returns
42   An object of type `io_result<std::size_t>` destructuring as `[ec, n]`. 42   An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
43   43  
44   Upon a contingency, `n` represents the number of bytes read so far, 44   Upon a contingency, `n` represents the number of bytes read so far,
45   inclusive of the last partial read. 45   inclusive of the last partial read.
46   46  
47   Contingencies: 47   Contingencies:
48   48  
49   @li The first contingency reported from awaiting @c stream.read_some 49   @li The first contingency reported from awaiting @c stream.read_some
50   while `buffers` is not yet filled. A contingency that accompanies 50   while `buffers` is not yet filled. A contingency that accompanies
51   the read which fills `buffers` is not reported: a completed 51   the read which fills `buffers` is not reported: a completed
52   transfer is a success. 52   transfer is a success.
53   53  
54   Notable conditions: 54   Notable conditions:
55   55  
56   @li @c cond::canceled — Operation was cancelled, 56   @li @c cond::canceled — Operation was cancelled,
57 - @li @c cond::eof — Stream reached end before @c buffers was filled. 57 + @li @c cond::eof — Stream reached end before `buffers` was filled.
58   58  
59   @par Await-postcondition 59   @par Await-postcondition
60   If `n == buffer_size(buffers)` the transfer completed and `ec` is 60   If `n == buffer_size(buffers)` the transfer completed and `ec` is
61   success; otherwise `ec` is set. 61   success; otherwise `ec` is set.
62   62  
63   @param stream The stream to read from. If the lifetime of `stream` ends 63   @param stream The stream to read from. If the lifetime of `stream` ends
64   before the coroutine finishes, the behavior is undefined. 64   before the coroutine finishes, the behavior is undefined.
65   65  
66   @param buffers The buffer sequence to fill. If the lifetime of the buffer 66   @param buffers The buffer sequence to fill. If the lifetime of the buffer
67   sequence represented by `buffers` ends before the coroutine finishes, the behavior is undefined. 67   sequence represented by `buffers` ends before the coroutine finishes, the behavior is undefined.
68   68  
69   69  
70   @par Remarks 70   @par Remarks
71   Supports _IoAwaitable cancellation_. 71   Supports _IoAwaitable cancellation_.
72   72  
73   73  
74   @par Example 74   @par Example
75   75  
76   @code 76   @code
77   capy::task<> process_message(capy::ReadStream auto& stream) 77   capy::task<> process_message(capy::ReadStream auto& stream)
78   { 78   {
79   std::vector<char> header(16); // known header size for some protocol 79   std::vector<char> header(16); // known header size for some protocol
80   auto [ec, n] = co_await capy::read(stream, capy::mutable_buffer(header)); 80   auto [ec, n] = co_await capy::read(stream, capy::mutable_buffer(header));
81   if (ec == capy::cond::eof) 81   if (ec == capy::cond::eof)
82   co_return; // Connection closed 82   co_return; // Connection closed
83   if (ec) 83   if (ec)
84   throw std::system_error(ec); 84   throw std::system_error(ec);
85   85  
86   // at this point `header` contains exactly 16 bytes 86   // at this point `header` contains exactly 16 bytes
87   } 87   }
88   @endcode 88   @endcode
89   89  
90   @see ReadStream, MutableBufferSequence 90   @see ReadStream, MutableBufferSequence
91   */ 91   */
92   template <typename S, typename MB> 92   template <typename S, typename MB>
93   requires ReadStream<S> && MutableBufferSequence<MB> 93   requires ReadStream<S> && MutableBufferSequence<MB>
94   auto 94   auto
HITCBC 95   98 read(S& stream, MB buffers) -> 95   98 read(S& stream, MB buffers) ->
96   io_task<std::size_t> 96   io_task<std::size_t>
97   { 97   {
98   auto consuming = buffer_slice(buffers); 98   auto consuming = buffer_slice(buffers);
99   std::size_t const total_size = buffer_size(buffers); 99   std::size_t const total_size = buffer_size(buffers);
100   std::size_t total_read = 0; 100   std::size_t total_read = 0;
101   101  
102   while(total_read < total_size) 102   while(total_read < total_size)
103   { 103   {
104   auto [ec, n] = co_await stream.read_some(consuming.data()); 104   auto [ec, n] = co_await stream.read_some(consuming.data());
105   consuming.remove_prefix(n); 105   consuming.remove_prefix(n);
106   total_read += n; 106   total_read += n;
107   // A contingency that still completed the transfer is a success: 107   // A contingency that still completed the transfer is a success:
108   // report it only when the buffer was not filled. 108   // report it only when the buffer was not filled.
109   if(ec && total_read < total_size) 109   if(ec && total_read < total_size)
110   co_return {ec, total_read}; 110   co_return {ec, total_read};
111   } 111   }
112   112  
113   co_return {{}, total_read}; 113   co_return {{}, total_read};
HITCBC 114   196 } 114   196 }
115   115  
116   /** Read all data from a stream into a dynamic buffer. 116   /** Read all data from a stream into a dynamic buffer.
117   117  
118   @par Await-effects 118   @par Await-effects
119   119  
120   Reads data from `stream` via awaiting `stream.read_some` repeatedly 120   Reads data from `stream` via awaiting `stream.read_some` repeatedly
121 - and appending it to `dynbuf` using prepare/commit semantics 121 + and appending the results to `dynbuf`,
122 - until: 122 + until a contingency occurs.
123 -  
124 - @li either @c dynbuf.size() == @c dynbuf.max_size() ,  
125 - @li or a contingency on @c stream.read_some occurs.  
126 -  
127 - The last, potenitally partial, read is also appended.  
128 -  
129 - The value passed in the first call to `dynbuf.prepare` is the smallest of  
130 - `initial_amount` and `dynbuf.max_size() - dynbuf.size()`. Value passed  
131 - to each subsequent call is 1.5 the value passed in the preceding call.  
132   123  
  124 + Data is appended using prepare/commit semantics.
  125 + The buffer grows with 1.5x factor when filled.
133   126  
134   @par Await-returns 127   @par Await-returns
135   128  
136   An object of type `io_result<std::size_t>` destructuring as `[ec, n]`. 129   An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
137   130  
138   `n` represents the total number of bytes read, 131   `n` represents the total number of bytes read,
139   inclusive of the last partial read. 132   inclusive of the last partial read.
140   133  
141   Contingencies: 134   Contingencies:
142   135  
143   @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some . 136   @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some .
144 -  
145   137  
146   @par Await-throws 138   @par Await-throws
147 - 139 + `std::bad_alloc` when append to `dynbuf` fails.
148 - Whatever operations on @c dunbuf throw.  
149 -  
150 - (Note: types modeling @c DynamicBufferParam provided by Capy throw  
151 - @c std::bad_alloc from member function  
152 - @c prepare .)  
153 -  
154   140  
155   @param stream The stream to read from. If the lifetime of `stream` ends 141   @param stream The stream to read from. If the lifetime of `stream` ends
156   before the coroutine finishes, the behavior is undefined. 142   before the coroutine finishes, the behavior is undefined.
157   143  
158   @param dynbuf The dynamic buffer to append data to. If the lifetime of the buffer 144   @param dynbuf The dynamic buffer to append data to. If the lifetime of the buffer
159   sequence represented by `dynbuf` ends before the coroutine finishes, the behavior is undefined. 145   sequence represented by `dynbuf` ends before the coroutine finishes, the behavior is undefined.
160   146  
161 - @param initial_amount Hint for the value to be passed in the initial call to `dynbuf.prepare()` 147 + @param initial_amount Initial bytes to prepare (default 2048).
162 - (default 2048).  
163   148  
164   149  
165   @par Remarks 150   @par Remarks
166   Supports _IoAwaitable cancellation_. 151   Supports _IoAwaitable cancellation_.
167   152  
168   @par Example 153   @par Example
169   154  
170   @code 155   @code
171   capy::task<std::string> read_body(capy::ReadStream auto& stream) 156   capy::task<std::string> read_body(capy::ReadStream auto& stream)
172   { 157   {
173   std::string body; 158   std::string body;
174   auto [ec, n] = co_await capy::read(stream, capy::dynamic_buffer(body)); 159   auto [ec, n] = co_await capy::read(stream, capy::dynamic_buffer(body));
175   if (ec) 160   if (ec)
176   throw std::system_error(ec); 161   throw std::system_error(ec);
177   return body; 162   return body;
178   } 163   }
179   @endcode 164   @endcode
180   165  
181   @see read_some, ReadStream, DynamicBufferParam 166   @see read_some, ReadStream, DynamicBufferParam
182   */ 167   */
183   template <typename S, typename DB> 168   template <typename S, typename DB>
184   requires ReadStream<S> && DynamicBufferParam<DB> 169   requires ReadStream<S> && DynamicBufferParam<DB>
185   auto 170   auto
HITCBC 186   80 read( 171   80 read(
187   S& stream, 172   S& stream,
188   DB&& dynbuf, 173   DB&& dynbuf,
189   std::size_t initial_amount = 2048) -> 174   std::size_t initial_amount = 2048) ->
190   io_task<std::size_t> 175   io_task<std::size_t>
191   { 176   {
192   std::size_t amount = initial_amount; 177   std::size_t amount = initial_amount;
193   std::size_t total_read = 0; 178   std::size_t total_read = 0;
194   for(;;) 179   for(;;)
195   { 180   {
196   auto mb = dynbuf.prepare(amount); 181   auto mb = dynbuf.prepare(amount);
197   auto const mb_size = buffer_size(mb); 182   auto const mb_size = buffer_size(mb);
198   auto [ec, n] = co_await stream.read_some(mb); 183   auto [ec, n] = co_await stream.read_some(mb);
199   dynbuf.commit(n); 184   dynbuf.commit(n);
200   total_read += n; 185   total_read += n;
201   if(ec == cond::eof) 186   if(ec == cond::eof)
202   co_return {{}, total_read}; 187   co_return {{}, total_read};
203   if(ec) 188   if(ec)
204   co_return {ec, total_read}; 189   co_return {ec, total_read};
205   if(n == mb_size) 190   if(n == mb_size)
206   amount = amount / 2 + amount; 191   amount = amount / 2 + amount;
207   } 192   }
HITCBC 208   160 } 193   160 }
209   194  
210   /** Read all data from a source into a dynamic buffer. 195   /** Read all data from a source into a dynamic buffer.
211   196  
212   @par Await-effects 197   @par Await-effects
213   198  
214   Reads data from `stream` by calling `source.read` repeatedly 199   Reads data from `stream` by calling `source.read` repeatedly
215 - and appending it to `dynbuf` using prepare/commit semantics 200 + and appending it to `dynbuf` until a contingency occurs.
216 - until:  
217 -  
218 - @li either @c dynbuf.size() == @c dynbuf.max_size() ,  
219 - @li or a contingency on @c stream.read occurs.  
220 -  
221   The last, potenitally partial, read is also appended. 201   The last, potenitally partial, read is also appended.
222   202  
223 - The value passed in the first call to `dynbuf.prepare` is the smallest of 203 + Data is appended using prepare/commit semantics.
224 - `initial_amount` and `dynbuf.max_size() - dynbuf.size()`. Value passed 204 + The buffer grows with 1.5x factor when filled.
225 - to each subsequent call is 1.5 the value passed in the preceding call.  
226 -  
227   205  
228   @par Await-returns 206   @par Await-returns
229   207  
230   An object of type `io_result<std::size_t>` destructuring as `[ec, n]`. 208   An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
231   209  
232   `n` represents the total number of bytes read, 210   `n` represents the total number of bytes read,
233   inclusive of the last partial read. 211   inclusive of the last partial read.
234   212  
235   213  
236   Contingencies: 214   Contingencies:
237   215  
238   @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some . 216   @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some .
239 -  
240   217  
241 -  
242 - Whatever operations on @c dunbuf throw.  
243   @par Await-throws 218   @par Await-throws
244   219  
245 - (Note: types modeling @c DynamicBufferParam provided by Capy throw 220 + `std::bad_alloc` when append to `dynbuf` fails.
246 - @c std::bad_alloc from member function  
247 - @c prepare .)  
248 -  
249   221  
250   @param source The source to read from. If the lifetime of `source` ends 222   @param source The source to read from. If the lifetime of `source` ends
251   before the coroutine finishes, the behavior is undefined. 223   before the coroutine finishes, the behavior is undefined.
252   224  
253   @param dynbuf The dynamic buffer to append data to. If the lifetime of the 225   @param dynbuf The dynamic buffer to append data to. If the lifetime of the
254   buffer sequence represented by `dynbuf` ends before the coroutine finishes, 226   buffer sequence represented by `dynbuf` ends before the coroutine finishes,
255   the behavior is undefined. 227   the behavior is undefined.
256   228  
257 - @param initial_amount Hint for the value to be passed in the initial call to `dynbuf.prepare()` 229 + @param initial_amount Initial bytes to prepare (default 2048).
258 - (default 2048).  
259   230  
260   @par Remarks 231   @par Remarks
261   Supports _IoAwaitable cancellation_. 232   Supports _IoAwaitable cancellation_.
262   233  
263   @par Example 234   @par Example
264   235  
265   @code 236   @code
266   capy::task<std::string> read_body(capy::ReadSource auto& source) 237   capy::task<std::string> read_body(capy::ReadSource auto& source)
267   { 238   {
268   std::string body; 239   std::string body;
269   auto [ec, n] = co_await capy::read(source, capy::dynamic_buffer(body)); 240   auto [ec, n] = co_await capy::read(source, capy::dynamic_buffer(body));
270   if (ec) 241   if (ec)
271   throw std::system_error(ec); 242   throw std::system_error(ec);
272   return body; 243   return body;
273   } 244   }
274   @endcode 245   @endcode
275   246  
276   @see ReadSource, DynamicBufferParam 247   @see ReadSource, DynamicBufferParam
277   */ 248   */
278   template <typename S, typename DB> 249   template <typename S, typename DB>
279   requires ReadSource<S> && DynamicBufferParam<DB> 250   requires ReadSource<S> && DynamicBufferParam<DB>
280   auto 251   auto
HITCBC 281   54 read( 252   54 read(
282   S& source, 253   S& source,
283   DB&& dynbuf, 254   DB&& dynbuf,
284   std::size_t initial_amount = 2048) -> 255   std::size_t initial_amount = 2048) ->
285   io_task<std::size_t> 256   io_task<std::size_t>
286   { 257   {
287   std::size_t amount = initial_amount; 258   std::size_t amount = initial_amount;
288   std::size_t total_read = 0; 259   std::size_t total_read = 0;
289   for(;;) 260   for(;;)
290   { 261   {
291   auto mb = dynbuf.prepare(amount); 262   auto mb = dynbuf.prepare(amount);
292   auto const mb_size = buffer_size(mb); 263   auto const mb_size = buffer_size(mb);
293   auto [ec, n] = co_await source.read(mb); 264   auto [ec, n] = co_await source.read(mb);
294   dynbuf.commit(n); 265   dynbuf.commit(n);
295   total_read += n; 266   total_read += n;
296   if(ec == cond::eof) 267   if(ec == cond::eof)
297   co_return {{}, total_read}; 268   co_return {{}, total_read};
298   if(ec) 269   if(ec)
299   co_return {ec, total_read}; 270   co_return {ec, total_read};
300   if(n == mb_size) 271   if(n == mb_size)
301   amount = amount / 2 + amount; // 1.5x growth 272   amount = amount / 2 + amount; // 1.5x growth
302   } 273   }
HITCBC 303   108 } 274   108 }
304   275  
305   } // namespace capy 276   } // namespace capy
306   } // namespace boost 277   } // namespace boost
307   278  
308   #endif 279   #endif