. /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. 36 + @li or a contingency occurs on `stream.read_some`.
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 `buffers` was filled. 57 + @li @c cond::eof — Stream reached end before @c 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 the results to `dynbuf`, 121 + and appending it to `dynbuf` using prepare/commit semantics
122 - until a contingency occurs. 122 + until:
  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.
123 - Data is appended using prepare/commit semantics.  
124 - The buffer grows with 1.5x factor when filled.  
125   132  
126   133  
127   @par Await-returns 134   @par Await-returns
128   135  
129   An object of type `io_result<std::size_t>` destructuring as `[ec, n]`. 136   An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
130   137  
131   `n` represents the total number of bytes read, 138   `n` represents the total number of bytes read,
132   inclusive of the last partial read. 139   inclusive of the last partial read.
133   140  
134   Contingencies: 141   Contingencies:
135   142  
136   @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some . 143   @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some .
137   144  
  145 +
138   @par Await-throws 146   @par Await-throws
139 - `std::bad_alloc` when append to `dynbuf` fails. 147 +
  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 +
140   154  
141   @param stream The stream to read from. If the lifetime of `stream` ends 155   @param stream The stream to read from. If the lifetime of `stream` ends
142   before the coroutine finishes, the behavior is undefined. 156   before the coroutine finishes, the behavior is undefined.
143   157  
144   @param dynbuf The dynamic buffer to append data to. If the lifetime of the buffer 158   @param dynbuf The dynamic buffer to append data to. If the lifetime of the buffer
145   sequence represented by `dynbuf` ends before the coroutine finishes, the behavior is undefined. 159   sequence represented by `dynbuf` ends before the coroutine finishes, the behavior is undefined.
146   160  
147 - @param initial_amount Initial bytes to prepare (default 2048). 161 + @param initial_amount Hint for the value to be passed in the initial call to `dynbuf.prepare()`
  162 + (default 2048).
148   163  
149   164  
150   @par Remarks 165   @par Remarks
151   Supports _IoAwaitable cancellation_. 166   Supports _IoAwaitable cancellation_.
152   167  
153   @par Example 168   @par Example
154   169  
155   @code 170   @code
156   capy::task<std::string> read_body(capy::ReadStream auto& stream) 171   capy::task<std::string> read_body(capy::ReadStream auto& stream)
157   { 172   {
158   std::string body; 173   std::string body;
159   auto [ec, n] = co_await capy::read(stream, capy::dynamic_buffer(body)); 174   auto [ec, n] = co_await capy::read(stream, capy::dynamic_buffer(body));
160   if (ec) 175   if (ec)
161   throw std::system_error(ec); 176   throw std::system_error(ec);
162   return body; 177   return body;
163   } 178   }
164   @endcode 179   @endcode
165   180  
166   @see read_some, ReadStream, DynamicBufferParam 181   @see read_some, ReadStream, DynamicBufferParam
167   */ 182   */
168   template <typename S, typename DB> 183   template <typename S, typename DB>
169   requires ReadStream<S> && DynamicBufferParam<DB> 184   requires ReadStream<S> && DynamicBufferParam<DB>
170   auto 185   auto
HITCBC 171   80 read( 186   80 read(
172   S& stream, 187   S& stream,
173   DB&& dynbuf, 188   DB&& dynbuf,
174   std::size_t initial_amount = 2048) -> 189   std::size_t initial_amount = 2048) ->
175   io_task<std::size_t> 190   io_task<std::size_t>
176   { 191   {
177   std::size_t amount = initial_amount; 192   std::size_t amount = initial_amount;
178   std::size_t total_read = 0; 193   std::size_t total_read = 0;
179   for(;;) 194   for(;;)
180   { 195   {
181   auto mb = dynbuf.prepare(amount); 196   auto mb = dynbuf.prepare(amount);
182   auto const mb_size = buffer_size(mb); 197   auto const mb_size = buffer_size(mb);
183   auto [ec, n] = co_await stream.read_some(mb); 198   auto [ec, n] = co_await stream.read_some(mb);
184   dynbuf.commit(n); 199   dynbuf.commit(n);
185   total_read += n; 200   total_read += n;
186   if(ec == cond::eof) 201   if(ec == cond::eof)
187   co_return {{}, total_read}; 202   co_return {{}, total_read};
188   if(ec) 203   if(ec)
189   co_return {ec, total_read}; 204   co_return {ec, total_read};
190   if(n == mb_size) 205   if(n == mb_size)
191   amount = amount / 2 + amount; 206   amount = amount / 2 + amount;
192   } 207   }
HITCBC 193   160 } 208   160 }
194   209  
195   /** Read all data from a source into a dynamic buffer. 210   /** Read all data from a source into a dynamic buffer.
196   211  
197   @par Await-effects 212   @par Await-effects
198   213  
199   Reads data from `stream` by calling `source.read` repeatedly 214   Reads data from `stream` by calling `source.read` repeatedly
200 - and appending it to `dynbuf` until a contingency occurs. 215 + and appending it to `dynbuf` using prepare/commit semantics
  216 + until:
  217 +
  218 + @li either @c dynbuf.size() == @c dynbuf.max_size() ,
  219 + @li or a contingency on @c stream.read occurs.
  220 +
201   The last, potenitally partial, read is also appended. 221   The last, potenitally partial, read is also appended.
202   222  
203 - Data is appended using prepare/commit semantics. 223 + The value passed in the first call to `dynbuf.prepare` is the smallest of
204 - The buffer grows with 1.5x factor when filled. 224 + `initial_amount` and `dynbuf.max_size() - dynbuf.size()`. Value passed
  225 + to each subsequent call is 1.5 the value passed in the preceding call.
  226 +
205   227  
206   @par Await-returns 228   @par Await-returns
207   229  
208   An object of type `io_result<std::size_t>` destructuring as `[ec, n]`. 230   An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
209   231  
210   `n` represents the total number of bytes read, 232   `n` represents the total number of bytes read,
211   inclusive of the last partial read. 233   inclusive of the last partial read.
212   234  
213   235  
214   Contingencies: 236   Contingencies:
215   237  
216   @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some . 238   @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some .
217   239  
  240 +
218   @par Await-throws 241   @par Await-throws
  242 +
  243 + Whatever operations on @c dunbuf throw.
219   244  
220 - `std::bad_alloc` when append to `dynbuf` fails. 245 + (Note: types modeling @c DynamicBufferParam provided by Capy throw
  246 + @c std::bad_alloc from member function
  247 + @c prepare .)
  248 +
221   249  
222   @param source The source to read from. If the lifetime of `source` ends 250   @param source The source to read from. If the lifetime of `source` ends
223   before the coroutine finishes, the behavior is undefined. 251   before the coroutine finishes, the behavior is undefined.
224   252  
225   @param dynbuf The dynamic buffer to append data to. If the lifetime of the 253   @param dynbuf The dynamic buffer to append data to. If the lifetime of the
226   buffer sequence represented by `dynbuf` ends before the coroutine finishes, 254   buffer sequence represented by `dynbuf` ends before the coroutine finishes,
227   the behavior is undefined. 255   the behavior is undefined.
228   256  
229 - @param initial_amount Initial bytes to prepare (default 2048). 257 + @param initial_amount Hint for the value to be passed in the initial call to `dynbuf.prepare()`
  258 + (default 2048).
230   259  
231   @par Remarks 260   @par Remarks
232   Supports _IoAwaitable cancellation_. 261   Supports _IoAwaitable cancellation_.
233   262  
234   @par Example 263   @par Example
235   264  
236   @code 265   @code
237   capy::task<std::string> read_body(capy::ReadSource auto& source) 266   capy::task<std::string> read_body(capy::ReadSource auto& source)
238   { 267   {
239   std::string body; 268   std::string body;
240   auto [ec, n] = co_await capy::read(source, capy::dynamic_buffer(body)); 269   auto [ec, n] = co_await capy::read(source, capy::dynamic_buffer(body));
241   if (ec) 270   if (ec)
242   throw std::system_error(ec); 271   throw std::system_error(ec);
243   return body; 272   return body;
244   } 273   }
245   @endcode 274   @endcode
246   275  
247   @see ReadSource, DynamicBufferParam 276   @see ReadSource, DynamicBufferParam
248   */ 277   */
249   template <typename S, typename DB> 278   template <typename S, typename DB>
250   requires ReadSource<S> && DynamicBufferParam<DB> 279   requires ReadSource<S> && DynamicBufferParam<DB>
251   auto 280   auto
HITCBC 252   54 read( 281   54 read(
253   S& source, 282   S& source,
254   DB&& dynbuf, 283   DB&& dynbuf,
255   std::size_t initial_amount = 2048) -> 284   std::size_t initial_amount = 2048) ->
256   io_task<std::size_t> 285   io_task<std::size_t>
257   { 286   {
258   std::size_t amount = initial_amount; 287   std::size_t amount = initial_amount;
259   std::size_t total_read = 0; 288   std::size_t total_read = 0;
260   for(;;) 289   for(;;)
261   { 290   {
262   auto mb = dynbuf.prepare(amount); 291   auto mb = dynbuf.prepare(amount);
263   auto const mb_size = buffer_size(mb); 292   auto const mb_size = buffer_size(mb);
264   auto [ec, n] = co_await source.read(mb); 293   auto [ec, n] = co_await source.read(mb);
265   dynbuf.commit(n); 294   dynbuf.commit(n);
266   total_read += n; 295   total_read += n;
267   if(ec == cond::eof) 296   if(ec == cond::eof)
268   co_return {{}, total_read}; 297   co_return {{}, total_read};
269   if(ec) 298   if(ec)
270   co_return {ec, total_read}; 299   co_return {ec, total_read};
271   if(n == mb_size) 300   if(n == mb_size)
272   amount = amount / 2 + amount; // 1.5x growth 301   amount = amount / 2 + amount; // 1.5x growth
273   } 302   }
HITCBC 274   108 } 303   108 }
275   304  
276   } // namespace capy 305   } // namespace capy
277   } // namespace boost 306   } // namespace boost
278   307  
279   #endif 308   #endif