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include/boost/capy/write.hpp

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write.hpp
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boost::capy::task<boost::capy::io_result<unsigned long> > boost::capy::write<boost::capy::contingent_write_stream, boost::capy::const_buffer>(boost::capy::contingent_write_stream&, boost::capy::const_buffer) :95 2x 100.0% 44.0% boost::capy::task<boost::capy::io_result<unsigned long> > boost::capy::write<boost::capy::test::write_stream, boost::capy::const_buffer>(boost::capy::test::write_stream&, boost::capy::const_buffer) :95 20x 100.0% 44.0% boost::capy::task<boost::capy::io_result<unsigned long> > boost::capy::write<boost::capy::test::write_stream, std::array<boost::capy::const_buffer, 2ul> >(boost::capy::test::write_stream&, std::array<boost::capy::const_buffer, 2ul>) :95 30x 100.0% 44.0%
Line TLA Hits 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_WRITE_HPP
11 #define BOOST_CAPY_WRITE_HPP
12
13 #include <boost/capy/detail/config.hpp>
14 #include <boost/capy/io_task.hpp>
15 #include <boost/capy/buffers.hpp>
16 #include <boost/capy/buffers/buffer_slice.hpp>
17 #include <boost/capy/concept/write_stream.hpp>
18 #include <system_error>
19
20 #include <cstddef>
21
22 namespace boost {
23 namespace capy {
24
25 /** Write an entire buffer sequence to a stream.
26
27 @par Await-effects
28
29 Writes the contents of `buffers` to `stream` via awaiting
30 `stream.write_some` with consecutive portions of data from `buffers`
31 until:
32
33 @li either the full content of @c buffers is processed,
34 @li or a contingency occurs.
35
36 If `buffer_size(buffers) == 0` then no awaiting `stream.write_some`
37 is performed. This is not a contingency.
38
39
40 @par Await-returns
41
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 written
45 so far.
46
47 Otherwise `n` represents the number of bytes written.
48
49 Contingencies:
50
51 @li The first contingency reported from awaiting @c stream.write_some
52 while not all bytes have been written. A contingency that accompanies
53 the write which transfers the last bytes is not reported: a completed
54 transfer is a success.
55
56 Notable conditions:
57
58 @li @c cond::canceled — Operation was cancelled,
59 @li @c std::errc::broken_pipe — Peer closed connection.
60
61
62 @par Await-postcondition
63
64 If `n == buffer_size(buffers)` the transfer completed and `ec` is
65 success; otherwise `ec` is set.
66
67
68 @param stream The stream to write to. If the lifetime of `stream` ends
69 before the coroutine finishes, the behavior is undefined.
70
71 @param buffers The buffer sequence to write. If the lifetime of the buffer
72 sequence represented by `buffers` ends
73 before the coroutine finishes, the behavior is undefined.
74
75 @par Remarks
76
77 Supports _IoAwaitable cancellation_.
78
79 @par Example
80
81 @code
82 capy::task<> send_response(capy::WriteStream auto& stream, std::string_view body)
83 {
84 auto [ec, n] = co_await capy::write(stream, capy::make_buffer(body));
85 if (ec)
86 throw std::system_error(ec);
87
88 // All bytes written successfully
89 }
90 @endcode
91
92 @see WriteStream, ConstBufferSequence, IoAwaitable, io_result, cond.
93 */
94 template <WriteStream S, ConstBufferSequence CB>
95 52x auto write(S& stream, CB buffers) -> io_task<std::size_t>
96 {
97 auto consuming = buffer_slice(buffers);
98 std::size_t const total_size = buffer_size(buffers);
99 std::size_t total_written = 0;
100
101 while(total_written < total_size)
102 {
103 auto [ec, n] = co_await stream.write_some(consuming.data());
104 consuming.remove_prefix(n);
105 total_written += n;
106 // A contingency that still completed the transfer is a success:
107 // report it only when not all bytes were written.
108 if(ec && total_written < total_size)
109 co_return {ec, total_written};
110 }
111
112 co_return {{}, total_written};
113 104x }
114
115 } // namespace capy
116 } // namespace boost
117
118 #endif
119