TLA Line data 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 HIT 98 : 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};
114 196 : }
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 80 : 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 : }
208 160 : }
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 54 : 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 : }
303 108 : }
304 :
305 : } // namespace capy
306 : } // namespace boost
307 :
308 : #endif
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