. /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.
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
  51 + the read which fills `buffers` is not reported: a completed
  52 + transfer is a success.
50   53  
51   Notable conditions: 54   Notable conditions:
52   55  
53   @li @c cond::canceled — Operation was cancelled, 56   @li @c cond::canceled — Operation was cancelled,
54   @li @c cond::eof — Stream reached end before `buffers` was filled. 57   @li @c cond::eof — Stream reached end before `buffers` was filled.
55   58  
56   @par Await-postcondition 59   @par Await-postcondition
57 - `ec || n == buffer_size(buffers)`. 60 + If `n == buffer_size(buffers)` the transfer completed and `ec` is
  61 + success; otherwise `ec` is set.
58   62  
59   @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
60   before the coroutine finishes, the behavior is undefined. 64   before the coroutine finishes, the behavior is undefined.
61   65  
62   @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
63   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.
64   68  
65   69  
66   @par Remarks 70   @par Remarks
67   Supports _IoAwaitable cancellation_. 71   Supports _IoAwaitable cancellation_.
68   72  
69   73  
70   @par Example 74   @par Example
71   75  
72   @code 76   @code
73   capy::task<> process_message(capy::ReadStream auto& stream) 77   capy::task<> process_message(capy::ReadStream auto& stream)
74   { 78   {
75   std::vector<char> header(16); // known header size for some protocol 79   std::vector<char> header(16); // known header size for some protocol
76   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));
77   if (ec == capy::cond::eof) 81   if (ec == capy::cond::eof)
78   co_return; // Connection closed 82   co_return; // Connection closed
79   if (ec) 83   if (ec)
80   throw std::system_error(ec); 84   throw std::system_error(ec);
81   85  
82   // at this point `header` contains exactly 16 bytes 86   // at this point `header` contains exactly 16 bytes
83   } 87   }
84   @endcode 88   @endcode
85   89  
86   @see ReadStream, MutableBufferSequence 90   @see ReadStream, MutableBufferSequence
87   */ 91   */
88   template <typename S, typename MB> 92   template <typename S, typename MB>
89   requires ReadStream<S> && MutableBufferSequence<MB> 93   requires ReadStream<S> && MutableBufferSequence<MB>
90   auto 94   auto
HITCBC 91   94 read(S& stream, MB buffers) -> 95   98 read(S& stream, MB buffers) ->
92   io_task<std::size_t> 96   io_task<std::size_t>
93   { 97   {
94   auto consuming = buffer_slice(buffers); 98   auto consuming = buffer_slice(buffers);
95   std::size_t const total_size = buffer_size(buffers); 99   std::size_t const total_size = buffer_size(buffers);
96   std::size_t total_read = 0; 100   std::size_t total_read = 0;
97   101  
98   while(total_read < total_size) 102   while(total_read < total_size)
99   { 103   {
100   auto [ec, n] = co_await stream.read_some(consuming.data()); 104   auto [ec, n] = co_await stream.read_some(consuming.data());
101   consuming.remove_prefix(n); 105   consuming.remove_prefix(n);
102   total_read += n; 106   total_read += n;
103 - if(ec) 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)
104   co_return {ec, total_read}; 110   co_return {ec, total_read};
105   } 111   }
106   112  
107   co_return {{}, total_read}; 113   co_return {{}, total_read};
HITCBC 108   188 } 114   196 }
109   115  
110   /** Read all data from a stream into a dynamic buffer. 116   /** Read all data from a stream into a dynamic buffer.
111   117  
112   @par Await-effects 118   @par Await-effects
113   119  
114   Reads data from `stream` via awaiting `stream.read_some` repeatedly 120   Reads data from `stream` via awaiting `stream.read_some` repeatedly
115   and appending the results to `dynbuf`, 121   and appending the results to `dynbuf`,
116   until a contingency occurs. 122   until a contingency occurs.
117   123  
118   Data is appended using prepare/commit semantics. 124   Data is appended using prepare/commit semantics.
119   The buffer grows with 1.5x factor when filled. 125   The buffer grows with 1.5x factor when filled.
120   126  
121   @par Await-returns 127   @par Await-returns
122   128  
123   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]`.
124   130  
125   `n` represents the total number of bytes read, 131   `n` represents the total number of bytes read,
126   inclusive of the last partial read. 132   inclusive of the last partial read.
127   133  
128   Contingencies: 134   Contingencies:
129   135  
130   @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 .
131   137  
132   @par Await-throws 138   @par Await-throws
133   `std::bad_alloc` when append to `dynbuf` fails. 139   `std::bad_alloc` when append to `dynbuf` fails.
134   140  
135   @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
136   before the coroutine finishes, the behavior is undefined. 142   before the coroutine finishes, the behavior is undefined.
137   143  
138   @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
139   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.
140   146  
141   @param initial_amount Initial bytes to prepare (default 2048). 147   @param initial_amount Initial bytes to prepare (default 2048).
142   148  
143   149  
144   @par Remarks 150   @par Remarks
145   Supports _IoAwaitable cancellation_. 151   Supports _IoAwaitable cancellation_.
146   152  
147   @par Example 153   @par Example
148   154  
149   @code 155   @code
150   capy::task<std::string> read_body(capy::ReadStream auto& stream) 156   capy::task<std::string> read_body(capy::ReadStream auto& stream)
151   { 157   {
152   std::string body; 158   std::string body;
153   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));
154   if (ec) 160   if (ec)
155   throw std::system_error(ec); 161   throw std::system_error(ec);
156   return body; 162   return body;
157   } 163   }
158   @endcode 164   @endcode
159   165  
160   @see read_some, ReadStream, DynamicBufferParam 166   @see read_some, ReadStream, DynamicBufferParam
161   */ 167   */
162   template <typename S, typename DB> 168   template <typename S, typename DB>
163   requires ReadStream<S> && DynamicBufferParam<DB> 169   requires ReadStream<S> && DynamicBufferParam<DB>
164   auto 170   auto
HITCBC 165   80 read( 171   80 read(
166   S& stream, 172   S& stream,
167   DB&& dynbuf, 173   DB&& dynbuf,
168   std::size_t initial_amount = 2048) -> 174   std::size_t initial_amount = 2048) ->
169   io_task<std::size_t> 175   io_task<std::size_t>
170   { 176   {
171   std::size_t amount = initial_amount; 177   std::size_t amount = initial_amount;
172   std::size_t total_read = 0; 178   std::size_t total_read = 0;
173   for(;;) 179   for(;;)
174   { 180   {
175   auto mb = dynbuf.prepare(amount); 181   auto mb = dynbuf.prepare(amount);
176   auto const mb_size = buffer_size(mb); 182   auto const mb_size = buffer_size(mb);
177   auto [ec, n] = co_await stream.read_some(mb); 183   auto [ec, n] = co_await stream.read_some(mb);
178   dynbuf.commit(n); 184   dynbuf.commit(n);
179   total_read += n; 185   total_read += n;
180   if(ec == cond::eof) 186   if(ec == cond::eof)
181   co_return {{}, total_read}; 187   co_return {{}, total_read};
182   if(ec) 188   if(ec)
183   co_return {ec, total_read}; 189   co_return {ec, total_read};
184   if(n == mb_size) 190   if(n == mb_size)
185   amount = amount / 2 + amount; 191   amount = amount / 2 + amount;
186   } 192   }
HITCBC 187   160 } 193   160 }
188   194  
189   /** Read all data from a source into a dynamic buffer. 195   /** Read all data from a source into a dynamic buffer.
190   196  
191   @par Await-effects 197   @par Await-effects
192   198  
193   Reads data from `stream` by calling `source.read` repeatedly 199   Reads data from `stream` by calling `source.read` repeatedly
194   and appending it to `dynbuf` until a contingency occurs. 200   and appending it to `dynbuf` until a contingency occurs.
195   The last, potenitally partial, read is also appended. 201   The last, potenitally partial, read is also appended.
196   202  
197   Data is appended using prepare/commit semantics. 203   Data is appended using prepare/commit semantics.
198   The buffer grows with 1.5x factor when filled. 204   The buffer grows with 1.5x factor when filled.
199   205  
200   @par Await-returns 206   @par Await-returns
201   207  
202   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]`.
203   209  
204   `n` represents the total number of bytes read, 210   `n` represents the total number of bytes read,
205   inclusive of the last partial read. 211   inclusive of the last partial read.
206   212  
207   213  
208   Contingencies: 214   Contingencies:
209   215  
210   @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 .
211   217  
212   @par Await-throws 218   @par Await-throws
213   219  
214   `std::bad_alloc` when append to `dynbuf` fails. 220   `std::bad_alloc` when append to `dynbuf` fails.
215   221  
216   @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
217   before the coroutine finishes, the behavior is undefined. 223   before the coroutine finishes, the behavior is undefined.
218   224  
219   @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
220   buffer sequence represented by `dynbuf` ends before the coroutine finishes, 226   buffer sequence represented by `dynbuf` ends before the coroutine finishes,
221   the behavior is undefined. 227   the behavior is undefined.
222   228  
223   @param initial_amount Initial bytes to prepare (default 2048). 229   @param initial_amount Initial bytes to prepare (default 2048).
224   230  
225   @par Remarks 231   @par Remarks
226   Supports _IoAwaitable cancellation_. 232   Supports _IoAwaitable cancellation_.
227   233  
228   @par Example 234   @par Example
229   235  
230   @code 236   @code
231   capy::task<std::string> read_body(capy::ReadSource auto& source) 237   capy::task<std::string> read_body(capy::ReadSource auto& source)
232   { 238   {
233   std::string body; 239   std::string body;
234   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));
235   if (ec) 241   if (ec)
236   throw std::system_error(ec); 242   throw std::system_error(ec);
237   return body; 243   return body;
238   } 244   }
239   @endcode 245   @endcode
240   246  
241   @see ReadSource, DynamicBufferParam 247   @see ReadSource, DynamicBufferParam
242   */ 248   */
243   template <typename S, typename DB> 249   template <typename S, typename DB>
244   requires ReadSource<S> && DynamicBufferParam<DB> 250   requires ReadSource<S> && DynamicBufferParam<DB>
245   auto 251   auto
HITCBC 246   54 read( 252   54 read(
247   S& source, 253   S& source,
248   DB&& dynbuf, 254   DB&& dynbuf,
249   std::size_t initial_amount = 2048) -> 255   std::size_t initial_amount = 2048) ->
250   io_task<std::size_t> 256   io_task<std::size_t>
251   { 257   {
252   std::size_t amount = initial_amount; 258   std::size_t amount = initial_amount;
253   std::size_t total_read = 0; 259   std::size_t total_read = 0;
254   for(;;) 260   for(;;)
255   { 261   {
256   auto mb = dynbuf.prepare(amount); 262   auto mb = dynbuf.prepare(amount);
257   auto const mb_size = buffer_size(mb); 263   auto const mb_size = buffer_size(mb);
258   auto [ec, n] = co_await source.read(mb); 264   auto [ec, n] = co_await source.read(mb);
259   dynbuf.commit(n); 265   dynbuf.commit(n);
260   total_read += n; 266   total_read += n;
261   if(ec == cond::eof) 267   if(ec == cond::eof)
262   co_return {{}, total_read}; 268   co_return {{}, total_read};
263   if(ec) 269   if(ec)
264   co_return {ec, total_read}; 270   co_return {ec, total_read};
265   if(n == mb_size) 271   if(n == mb_size)
266   amount = amount / 2 + amount; // 1.5x growth 272   amount = amount / 2 + amount; // 1.5x growth
267   } 273   }
HITCBC 268   108 } 274   108 }
269   275  
270   } // namespace capy 276   } // namespace capy
271   } // namespace boost 277   } // namespace boost
272   278  
273   #endif 279   #endif