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/consuming_buffers.hpp>
18 : #include <boost/capy/concept/read_stream.hpp>
19 :
20 : #include <algorithm>
21 : #include <cstddef>
22 :
23 : namespace boost {
24 : namespace capy {
25 :
26 : /** Read data from a stream until the buffer sequence is full.
27 :
28 : @par Await-effects
29 :
30 : Reads data from `stream` via awaiting `stream.read_some` repeatedly
31 : until:
32 :
33 : @li either the entire buffer sequence @c buffers is filled,
34 : @li or a contingency occurs on `stream.read_some`.
35 :
36 : If `buffer_size(buffers) == 0` then no awaiting `stream.read_some`
37 : is performed. This is not a contingency.
38 :
39 : @par Await-returns
40 : An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
41 :
42 : Upon a contingency, `n` represents the number of bytes read so far,
43 : inclusive of the last partial read.
44 :
45 : Contingencies:
46 :
47 : @li The first contingency reported from awaiting @c stream.read_some
48 : while `buffers` is not yet filled. A contingency that accompanies
49 : the read which fills `buffers` is not reported: a completed
50 : transfer is a success.
51 :
52 : Notable conditions:
53 :
54 : @li @c cond::canceled — Operation was cancelled,
55 : @li @c cond::eof — Stream reached end before @c buffers was filled.
56 :
57 : @par Await-postcondition
58 : If `n == buffer_size(buffers)` the transfer completed and `ec` is
59 : success; otherwise `ec` is set.
60 :
61 : @param stream The stream to read from. If the lifetime of `stream` ends
62 : before the coroutine finishes, the behavior is undefined.
63 :
64 : @param buffers The buffer sequence to fill. If the lifetime of the buffer
65 : sequence represented by `buffers` ends before the coroutine finishes, the behavior is undefined.
66 :
67 :
68 : @par Remarks
69 : Supports _IoAwaitable cancellation_.
70 :
71 :
72 : @par Example
73 :
74 : @code
75 : capy::task<> process_message(capy::ReadStream auto& stream)
76 : {
77 : std::vector<char> header(16); // known header size for some protocol
78 : auto [ec, n] = co_await capy::read(stream, capy::make_buffer(header));
79 : if (ec == capy::cond::eof)
80 : co_return; // Connection closed
81 : if (ec)
82 : throw std::system_error(ec);
83 :
84 : // at this point `header` contains exactly 16 bytes
85 : }
86 : @endcode
87 :
88 : @see ReadStream, MutableBufferSequence
89 : */
90 : template <typename S, typename MB>
91 : requires ReadStream<S> && MutableBufferSequence<MB>
92 : auto
93 HIT 98 : read(S& stream, MB buffers) ->
94 : io_task<std::size_t>
95 : {
96 : consuming_buffers consuming(buffers);
97 : std::size_t const total_size = buffer_size(buffers);
98 : std::size_t total_read = 0;
99 :
100 : while(total_read < total_size)
101 : {
102 : auto [ec, n] = co_await stream.read_some(consuming.data());
103 : consuming.consume(n);
104 : total_read += n;
105 : // A contingency that still completed the transfer is a success:
106 : // report it only when the buffer was not filled.
107 : if(ec && total_read < total_size)
108 : co_return {ec, total_read};
109 : }
110 :
111 : co_return {{}, total_read};
112 196 : }
113 :
114 : } // namespace capy
115 : } // namespace boost
116 :
117 : #endif
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