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include/boost/capy/read.hpp

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read.hpp
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boost::capy::task<boost::capy::io_result<unsigned long> > boost::capy::read<boost::capy::contingent_read_stream, boost::capy::mutable_buffer>(boost::capy::contingent_read_stream&, boost::capy::mutable_buffer) :95 4x 100.0% 44.0% boost::capy::task<boost::capy::io_result<unsigned long> > boost::capy::read<boost::capy::test::read_stream, boost::capy::mutable_buffer>(boost::capy::test::read_stream&, boost::capy::mutable_buffer) :95 22x 100.0% 44.0% boost::capy::task<boost::capy::io_result<unsigned long> > boost::capy::read<boost::capy::test::read_stream, std::array<boost::capy::mutable_buffer, 2ul> >(boost::capy::test::read_stream&, std::array<boost::capy::mutable_buffer, 2ul>) :95 34x 100.0% 44.0% boost::capy::task<boost::capy::io_result<unsigned long> > boost::capy::read<boost::capy::test::stream, boost::capy::mutable_buffer>(boost::capy::test::stream&, boost::capy::mutable_buffer) :95 38x 100.0% 44.0% boost::capy::task<boost::capy::io_result<unsigned long> > boost::capy::read<boost::capy::test::read_stream, boost::capy::basic_string_dynamic_buffer<char, std::char_traits<char>, std::allocator<char> >&>(boost::capy::test::read_stream&, boost::capy::basic_string_dynamic_buffer<char, std::char_traits<char>, std::allocator<char> >&, unsigned long) :186 50x 100.0% 44.0% boost::capy::task<boost::capy::io_result<unsigned long> > boost::capy::read<boost::capy::test::read_stream, boost::capy::circular_dynamic_buffer&>(boost::capy::test::read_stream&, boost::capy::circular_dynamic_buffer&, unsigned long) :186 30x 100.0% 44.0% boost::capy::task<boost::capy::io_result<unsigned long> > boost::capy::read<boost::capy::test::read_source, boost::capy::basic_string_dynamic_buffer<char, std::char_traits<char>, std::allocator<char> >&>(boost::capy::test::read_source&, boost::capy::basic_string_dynamic_buffer<char, std::char_traits<char>, std::allocator<char> >&, unsigned long) :281 30x 100.0% 44.0% boost::capy::task<boost::capy::io_result<unsigned long> > boost::capy::read<boost::capy::test::read_source, boost::capy::circular_dynamic_buffer&>(boost::capy::test::read_source&, boost::capy::circular_dynamic_buffer&, unsigned long) :281 24x 100.0% 44.0%
Line TLA Hits Source Code
1 //
2 // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3 //
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)
6 //
7 // Official repository: https://github.com/cppalliance/capy
8 //
9
10 #ifndef BOOST_CAPY_READ_HPP
11 #define BOOST_CAPY_READ_HPP
12
13 #include <boost/capy/detail/config.hpp>
14 #include <boost/capy/cond.hpp>
15 #include <boost/capy/io_task.hpp>
16 #include <boost/capy/buffers.hpp>
17 #include <boost/capy/buffers/buffer_slice.hpp>
18 #include <boost/capy/concept/dynamic_buffer.hpp>
19 #include <boost/capy/concept/read_source.hpp>
20 #include <boost/capy/concept/read_stream.hpp>
21 #include <system_error>
22
23 #include <cstddef>
24
25 namespace boost {
26 namespace capy {
27
28 /** Read data from a stream until the buffer sequence is full.
29
30 @par Await-effects
31
32 Reads data from `stream` via awaiting `stream.read_some` repeatedly
33 until:
34
35 @li either the entire buffer sequence @c buffers is filled,
36 @li or a contingency occurs on `stream.read_some`.
37
38 If `buffer_size(buffers) == 0` then no awaiting `stream.read_some`
39 is performed. This is not a contingency.
40
41 @par Await-returns
42 An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
43
44 Upon a contingency, `n` represents the number of bytes read so far,
45 inclusive of the last partial read.
46
47 Contingencies:
48
49 @li The first contingency reported from awaiting @c stream.read_some
50 while `buffers` is not yet filled. A contingency that accompanies
51 the read which fills `buffers` is not reported: a completed
52 transfer is a success.
53
54 Notable conditions:
55
56 @li @c cond::canceled — Operation was cancelled,
57 @li @c cond::eof — Stream reached end before @c buffers was filled.
58
59 @par Await-postcondition
60 If `n == buffer_size(buffers)` the transfer completed and `ec` is
61 success; otherwise `ec` is set.
62
63 @param stream The stream to read from. If the lifetime of `stream` ends
64 before the coroutine finishes, the behavior is undefined.
65
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.
68
69
70 @par Remarks
71 Supports _IoAwaitable cancellation_.
72
73
74 @par Example
75
76 @code
77 capy::task<> process_message(capy::ReadStream auto& stream)
78 {
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));
81 if (ec == capy::cond::eof)
82 co_return; // Connection closed
83 if (ec)
84 throw std::system_error(ec);
85
86 // at this point `header` contains exactly 16 bytes
87 }
88 @endcode
89
90 @see ReadStream, MutableBufferSequence
91 */
92 template <typename S, typename MB>
93 requires ReadStream<S> && MutableBufferSequence<MB>
94 auto
95 98x read(S& stream, MB buffers) ->
96 io_task<std::size_t>
97 {
98 auto consuming = buffer_slice(buffers);
99 std::size_t const total_size = buffer_size(buffers);
100 std::size_t total_read = 0;
101
102 while(total_read < total_size)
103 {
104 auto [ec, n] = co_await stream.read_some(consuming.data());
105 consuming.remove_prefix(n);
106 total_read += n;
107 // A contingency that still completed the transfer is a success:
108 // report it only when the buffer was not filled.
109 if(ec && total_read < total_size)
110 co_return {ec, total_read};
111 }
112
113 co_return {{}, total_read};
114 196x }
115
116 /** Read all data from a stream into a dynamic buffer.
117
118 @par Await-effects
119
120 Reads data from `stream` via awaiting `stream.read_some` repeatedly
121 and appending it to `dynbuf` using prepare/commit semantics
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.
132
133
134 @par Await-returns
135
136 An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
137
138 `n` represents the total number of bytes read,
139 inclusive of the last partial read.
140
141 Contingencies:
142
143 @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some .
144
145
146 @par Await-throws
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
154
155 @param stream The stream to read from. If the lifetime of `stream` ends
156 before the coroutine finishes, the behavior is undefined.
157
158 @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.
160
161 @param initial_amount Hint for the value to be passed in the initial call to `dynbuf.prepare()`
162 (default 2048).
163
164
165 @par Remarks
166 Supports _IoAwaitable cancellation_.
167
168 @par Example
169
170 @code
171 capy::task<std::string> read_body(capy::ReadStream auto& stream)
172 {
173 std::string body;
174 auto [ec, n] = co_await capy::read(stream, capy::dynamic_buffer(body));
175 if (ec)
176 throw std::system_error(ec);
177 return body;
178 }
179 @endcode
180
181 @see read_some, ReadStream, DynamicBufferParam
182 */
183 template <typename S, typename DB>
184 requires ReadStream<S> && DynamicBufferParam<DB>
185 auto
186 80x read(
187 S& stream,
188 DB&& dynbuf,
189 std::size_t initial_amount = 2048) ->
190 io_task<std::size_t>
191 {
192 std::size_t amount = initial_amount;
193 std::size_t total_read = 0;
194 for(;;)
195 {
196 auto mb = dynbuf.prepare(amount);
197 auto const mb_size = buffer_size(mb);
198 auto [ec, n] = co_await stream.read_some(mb);
199 dynbuf.commit(n);
200 total_read += n;
201 if(ec == cond::eof)
202 co_return {{}, total_read};
203 if(ec)
204 co_return {ec, total_read};
205 if(n == mb_size)
206 amount = amount / 2 + amount;
207 }
208 160x }
209
210 /** Read all data from a source into a dynamic buffer.
211
212 @par Await-effects
213
214 Reads data from `stream` by calling `source.read` repeatedly
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
221 The last, potenitally partial, read is also appended.
222
223 The value passed in the first call to `dynbuf.prepare` is the smallest of
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
227
228 @par Await-returns
229
230 An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
231
232 `n` represents the total number of bytes read,
233 inclusive of the last partial read.
234
235
236 Contingencies:
237
238 @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some .
239
240
241 @par Await-throws
242
243 Whatever operations on @c dunbuf throw.
244
245 (Note: types modeling @c DynamicBufferParam provided by Capy throw
246 @c std::bad_alloc from member function
247 @c prepare .)
248
249
250 @param source The source to read from. If the lifetime of `source` ends
251 before the coroutine finishes, the behavior is undefined.
252
253 @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,
255 the behavior is undefined.
256
257 @param initial_amount Hint for the value to be passed in the initial call to `dynbuf.prepare()`
258 (default 2048).
259
260 @par Remarks
261 Supports _IoAwaitable cancellation_.
262
263 @par Example
264
265 @code
266 capy::task<std::string> read_body(capy::ReadSource auto& source)
267 {
268 std::string body;
269 auto [ec, n] = co_await capy::read(source, capy::dynamic_buffer(body));
270 if (ec)
271 throw std::system_error(ec);
272 return body;
273 }
274 @endcode
275
276 @see ReadSource, DynamicBufferParam
277 */
278 template <typename S, typename DB>
279 requires ReadSource<S> && DynamicBufferParam<DB>
280 auto
281 54x read(
282 S& source,
283 DB&& dynbuf,
284 std::size_t initial_amount = 2048) ->
285 io_task<std::size_t>
286 {
287 std::size_t amount = initial_amount;
288 std::size_t total_read = 0;
289 for(;;)
290 {
291 auto mb = dynbuf.prepare(amount);
292 auto const mb_size = buffer_size(mb);
293 auto [ec, n] = co_await source.read(mb);
294 dynbuf.commit(n);
295 total_read += n;
296 if(ec == cond::eof)
297 co_return {{}, total_read};
298 if(ec)
299 co_return {ec, total_read};
300 if(n == mb_size)
301 amount = amount / 2 + amount; // 1.5x growth
302 }
303 108x }
304
305 } // namespace capy
306 } // namespace boost
307
308 #endif
309