TLA Line data Source code
1 : //
2 : // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3 : // Copyright (c) 2026 Michael Vandeberg
4 : //
5 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
6 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7 : //
8 : // Official repository: https://github.com/cppalliance/capy
9 : //
10 :
11 : #ifndef BOOST_CAPY_READ_HPP
12 : #define BOOST_CAPY_READ_HPP
13 :
14 : #include <boost/capy/detail/config.hpp>
15 : #include <boost/capy/cond.hpp>
16 : #include <boost/capy/io_task.hpp>
17 : #include <boost/capy/buffers.hpp>
18 : #include <boost/capy/buffers/consuming_buffers.hpp>
19 : #include <boost/capy/concept/read_stream.hpp>
20 :
21 : #include <algorithm>
22 : #include <cstddef>
23 :
24 : namespace boost {
25 : namespace capy {
26 :
27 : /** Read data from a stream until the buffer sequence is full.
28 :
29 : @par Await-effects
30 :
31 : Reads data from `stream` via awaiting `stream.read_some` repeatedly
32 : until:
33 :
34 : @li either the entire buffer sequence @c buffers is filled,
35 : @li or a contingency occurs on `stream.read_some`.
36 :
37 : If `buffer_size(buffers) == 0` then no awaiting `stream.read_some`
38 : is performed. This is not a contingency.
39 :
40 : @par Await-returns
41 : An object of type `io_result<std::size_t>` destructuring as `[ec, n]`.
42 :
43 : Upon a contingency, `n` represents the number of bytes read so far,
44 : inclusive of the last partial read.
45 :
46 : Contingencies:
47 :
48 : @li The first contingency reported from awaiting @c stream.read_some
49 : while `buffers` is not yet filled. A contingency that accompanies
50 : the read which fills `buffers` is not reported: a completed
51 : transfer is a success.
52 :
53 : Notable conditions:
54 :
55 : @li @c cond::canceled — Operation was cancelled,
56 : @li @c cond::eof — Stream reached end before @c buffers was filled.
57 :
58 : @par Await-postcondition
59 : If `n == buffer_size(buffers)` the transfer completed and `ec` is
60 : success; otherwise `ec` is set.
61 :
62 : @param stream The stream to read from. If the lifetime of `stream` ends
63 : before the coroutine finishes, the behavior is undefined.
64 :
65 : @param buffers The buffer sequence to fill. If the lifetime of the buffer
66 : sequence represented by `buffers` ends before the coroutine finishes, the behavior is undefined.
67 :
68 : @return A task yielding `io_result<std::size_t>` whose second element
69 : is the number of bytes read.
70 :
71 : @par Remarks
72 : Supports _IoAwaitable cancellation_.
73 :
74 :
75 : @par Example
76 :
77 : @code
78 : capy::task<> process_message(capy::ReadStream auto& stream)
79 : {
80 : std::vector<char> header(16); // known header size for some protocol
81 : auto [ec, n] = co_await capy::read(stream, capy::make_buffer(header));
82 : if (ec == capy::cond::eof)
83 : co_return; // Connection closed
84 : if (ec)
85 : throw std::system_error(ec);
86 :
87 : // at this point `header` contains exactly 16 bytes
88 : }
89 : @endcode
90 :
91 : @see ReadStream, MutableBufferSequence
92 : */
93 : template <typename S, typename MB>
94 : requires ReadStream<S> && MutableBufferSequence<MB>
95 : auto
96 HIT 99 : read(S& stream, MB buffers) ->
97 : io_task<std::size_t>
98 : {
99 : consuming_buffers consuming(buffers);
100 : std::size_t const total_size = buffer_size(buffers);
101 : std::size_t total_read = 0;
102 :
103 : while(total_read < total_size)
104 : {
105 : auto [ec, n] = co_await stream.read_some(consuming.data());
106 : consuming.consume(n);
107 : total_read += n;
108 : // A contingency that still completed the transfer is a success:
109 : // report it only when the buffer was not filled.
110 : if(ec && total_read < total_size)
111 : co_return {ec, total_read};
112 : }
113 :
114 : co_return {{}, total_read};
115 198 : }
116 :
117 : } // namespace capy
118 : } // namespace boost
119 :
120 : #endif
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