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 `initial_amount`.
130 : The value is grown to 1.5 times the preceding value only after a read that
131 : completely filled the prepared buffer; otherwise it is left unchanged for
132 : the next call.
133 :
134 :
135 : @par Await-returns
136 :
137 : An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
138 :
139 : `n` represents the total number of bytes read,
140 : inclusive of the last partial read.
141 :
142 : Contingencies:
143 :
144 : @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some .
145 :
146 :
147 : @par Await-throws
148 :
149 : Whatever operations on @c dunbuf throw.
150 :
151 : (Note: types modeling @c DynamicBufferParam provided by Capy throw
152 : @c std::bad_alloc from member function
153 : @c prepare .)
154 :
155 :
156 : @param stream The stream to read from. If the lifetime of `stream` ends
157 : before the coroutine finishes, the behavior is undefined.
158 :
159 : @param dynbuf The dynamic buffer to append data to. If the lifetime of the buffer
160 : sequence represented by `dynbuf` ends before the coroutine finishes, the behavior is undefined.
161 :
162 : @param initial_amount Hint for the value to be passed in the initial call to `dynbuf.prepare()`
163 : (default 2048).
164 :
165 :
166 : @par Remarks
167 : Supports _IoAwaitable cancellation_.
168 :
169 : @par Example
170 :
171 : @code
172 : capy::task<std::string> read_body(capy::ReadStream auto& stream)
173 : {
174 : std::string body;
175 : auto [ec, n] = co_await capy::read(stream, capy::dynamic_buffer(body));
176 : if (ec)
177 : throw std::system_error(ec);
178 : return body;
179 : }
180 : @endcode
181 :
182 : @see read_some, ReadStream, DynamicBufferParam
183 : */
184 : template <typename S, typename DB>
185 : requires ReadStream<S> && DynamicBufferParam<DB>
186 : auto
187 80 : read(
188 : S& stream,
189 : DB&& dynbuf,
190 : std::size_t initial_amount = 2048) ->
191 : io_task<std::size_t>
192 : {
193 : std::size_t amount = initial_amount;
194 : std::size_t total_read = 0;
195 : for(;;)
196 : {
197 : auto mb = dynbuf.prepare(amount);
198 : auto const mb_size = buffer_size(mb);
199 : auto [ec, n] = co_await stream.read_some(mb);
200 : dynbuf.commit(n);
201 : total_read += n;
202 : if(ec == cond::eof)
203 : co_return {{}, total_read};
204 : if(ec)
205 : co_return {ec, total_read};
206 : if(n == mb_size)
207 : amount = amount / 2 + amount;
208 : }
209 160 : }
210 :
211 : /** Read all data from a source into a dynamic buffer.
212 :
213 : @par Await-effects
214 :
215 : Reads data from `stream` by calling `source.read` repeatedly
216 : and appending it to `dynbuf` using prepare/commit semantics
217 : until:
218 :
219 : @li either @c dynbuf.size() == @c dynbuf.max_size() ,
220 : @li or a contingency on @c stream.read occurs.
221 :
222 : The last, potenitally partial, read is also appended.
223 :
224 : The value passed in the first call to `dynbuf.prepare` is `initial_amount`.
225 : The value is grown to 1.5 times the preceding value only after a read that
226 : completely filled the prepared buffer; otherwise it is left unchanged for
227 : the next call.
228 :
229 :
230 : @par Await-returns
231 :
232 : An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
233 :
234 : `n` represents the total number of bytes read,
235 : inclusive of the last partial read.
236 :
237 :
238 : Contingencies:
239 :
240 : @li The first contingency, other than one matching to @c cond::eof, reported from awaiting @c stream.read_some .
241 :
242 :
243 : @par Await-throws
244 :
245 : Whatever operations on @c dunbuf throw.
246 :
247 : (Note: types modeling @c DynamicBufferParam provided by Capy throw
248 : @c std::bad_alloc from member function
249 : @c prepare .)
250 :
251 :
252 : @param source The source to read from. If the lifetime of `source` ends
253 : before the coroutine finishes, the behavior is undefined.
254 :
255 : @param dynbuf The dynamic buffer to append data to. If the lifetime of the
256 : buffer sequence represented by `dynbuf` ends before the coroutine finishes,
257 : the behavior is undefined.
258 :
259 : @param initial_amount Hint for the value to be passed in the initial call to `dynbuf.prepare()`
260 : (default 2048).
261 :
262 : @par Remarks
263 : Supports _IoAwaitable cancellation_.
264 :
265 : @par Example
266 :
267 : @code
268 : capy::task<std::string> read_body(capy::ReadSource auto& source)
269 : {
270 : std::string body;
271 : auto [ec, n] = co_await capy::read(source, capy::dynamic_buffer(body));
272 : if (ec)
273 : throw std::system_error(ec);
274 : return body;
275 : }
276 : @endcode
277 :
278 : @see ReadSource, DynamicBufferParam
279 : */
280 : template <typename S, typename DB>
281 : requires ReadSource<S> && DynamicBufferParam<DB>
282 : auto
283 54 : read(
284 : S& source,
285 : DB&& dynbuf,
286 : std::size_t initial_amount = 2048) ->
287 : io_task<std::size_t>
288 : {
289 : std::size_t amount = initial_amount;
290 : std::size_t total_read = 0;
291 : for(;;)
292 : {
293 : auto mb = dynbuf.prepare(amount);
294 : auto const mb_size = buffer_size(mb);
295 : auto [ec, n] = co_await source.read(mb);
296 : dynbuf.commit(n);
297 : total_read += n;
298 : if(ec == cond::eof)
299 : co_return {{}, total_read};
300 : if(ec)
301 : co_return {ec, total_read};
302 : if(n == mb_size)
303 : amount = amount / 2 + amount; // 1.5x growth
304 : }
305 108 : }
306 :
307 : } // namespace capy
308 : } // namespace boost
309 :
310 : #endif
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