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_TEST_WRITE_STREAM_HPP
12 : #define BOOST_CAPY_TEST_WRITE_STREAM_HPP
13 :
14 : #include <boost/capy/detail/config.hpp>
15 : #include <boost/capy/buffers.hpp>
16 : #include <boost/capy/buffers/buffer_copy.hpp>
17 : #include <boost/capy/buffers/make_buffer.hpp>
18 : #include <coroutine>
19 : #include <boost/capy/ex/io_env.hpp>
20 : #include <boost/capy/io_result.hpp>
21 : #include <boost/capy/error.hpp>
22 : #include <boost/capy/test/fuse.hpp>
23 :
24 : #include <algorithm>
25 : #include <string>
26 : #include <string_view>
27 :
28 : namespace boost {
29 : namespace capy {
30 : namespace test {
31 :
32 : /** A mock stream for testing write operations.
33 :
34 : Use this to verify code that performs writes without needing
35 : real I/O. Call @ref write_some to write data, then @ref data
36 : to retrieve what was written. The associated @ref fuse enables
37 : error injection at controlled points. An optional
38 : `max_write_size` constructor parameter limits bytes per write
39 : to simulate chunked delivery.
40 :
41 : This class satisfies the @ref WriteStream concept.
42 :
43 : @par Thread Safety
44 : Not thread-safe.
45 :
46 : @par Example
47 : @code
48 : fuse f;
49 : write_stream ws( f );
50 :
51 : auto r = f.armed( [&]( fuse& ) -> task<void> {
52 : auto [ec, n] = co_await ws.write_some(
53 : const_buffer( "Hello", 5 ) );
54 : if( ec )
55 : co_return;
56 : // ws.data() returns "Hello"
57 : } );
58 : @endcode
59 :
60 : @see fuse, WriteStream
61 : */
62 : class write_stream
63 : {
64 : fuse f_;
65 : std::string data_;
66 : std::string expect_;
67 : std::size_t max_write_size_;
68 :
69 : std::error_code
70 HIT 959 : consume_match_() noexcept
71 : {
72 959 : if(data_.empty() || expect_.empty())
73 943 : return {};
74 16 : std::size_t const n = (std::min)(data_.size(), expect_.size());
75 16 : if(std::string_view(data_.data(), n) !=
76 32 : std::string_view(expect_.data(), n))
77 4 : return error::test_failure;
78 12 : data_.erase(0, n);
79 12 : expect_.erase(0, n);
80 12 : return {};
81 : }
82 :
83 : public:
84 : /** Construct a write stream.
85 :
86 : @param f The fuse used to inject errors during writes.
87 :
88 : @param max_write_size Maximum bytes transferred per write.
89 : Use to simulate chunked network delivery.
90 : */
91 1192 : explicit write_stream(
92 : fuse f = {},
93 : std::size_t max_write_size = std::size_t(-1)) noexcept
94 1192 : : f_(std::move(f))
95 1192 : , max_write_size_(max_write_size)
96 : {
97 1192 : }
98 :
99 : /// Return the written data as a string view.
100 : std::string_view
101 962 : data() const noexcept
102 : {
103 962 : return data_;
104 : }
105 :
106 : /** Set the expected data for subsequent writes.
107 :
108 : Stores the expected data and immediately tries to match
109 : against any data already written. Matched data is consumed
110 : from both buffers.
111 :
112 : @param sv The expected data.
113 :
114 : @return An error if existing data does not match.
115 : */
116 : std::error_code
117 30 : expect(std::string_view sv)
118 : {
119 30 : expect_.assign(sv);
120 30 : return consume_match_();
121 : }
122 :
123 : /// Return the number of bytes written.
124 : std::size_t
125 7 : size() const noexcept
126 : {
127 7 : return data_.size();
128 : }
129 :
130 : /** Asynchronously write data to the stream.
131 :
132 : Transfers up to `buffer_size( buffers )` bytes from the provided
133 : const buffer sequence to the internal buffer. Before every write,
134 : the attached @ref fuse is consulted to possibly inject an error
135 : for testing fault scenarios. The returned `std::size_t` is the
136 : number of bytes transferred.
137 :
138 : @par Effects
139 : On success, appends the written bytes to the internal buffer.
140 : If an error is injected by the fuse, the internal buffer remains
141 : unchanged.
142 :
143 : @par Exception Safety
144 : No-throw guarantee.
145 :
146 : @par Cancellation
147 : If the environment's stop token has been requested, the write
148 : completes immediately with `error::canceled` and transfers no
149 : data. An empty buffer sequence is a no-op that completes
150 : successfully regardless of the stop token.
151 :
152 : @param buffers The const buffer sequence containing data to write.
153 :
154 : @return An awaitable that await-returns `(error_code,std::size_t)`.
155 :
156 : @see fuse
157 : */
158 : template<ConstBufferSequence CB>
159 : auto
160 1194 : write_some(CB buffers)
161 : {
162 : struct awaitable
163 : {
164 : write_stream* self_;
165 : CB buffers_;
166 : bool canceled_ = false;
167 :
168 1194 : bool await_ready() const noexcept { return false; }
169 :
170 : // The operation completes synchronously, but await_suspend is
171 : // the only place io_env is delivered (the promise's
172 : // transform_awaiter forwards it here). Returning false means
173 : // the coroutine does not actually suspend; it resumes
174 : // immediately, having observed the stop token. See io_env,
175 : // IoAwaitable.
176 : bool
177 1194 : await_suspend(
178 : std::coroutine_handle<>,
179 : io_env const* env) noexcept
180 : {
181 1194 : canceled_ = env->stop_token.stop_requested();
182 1194 : return false;
183 : }
184 :
185 : io_result<std::size_t>
186 1194 : await_resume()
187 : {
188 1194 : if(buffer_empty(buffers_))
189 2 : return {{}, 0};
190 :
191 1192 : if(canceled_)
192 1 : return {error::canceled, 0};
193 :
194 1191 : auto ec = self_->f_.maybe_fail();
195 1060 : if(ec)
196 131 : return {ec, 0};
197 :
198 929 : std::size_t n = buffer_size(buffers_);
199 929 : n = (std::min)(n, self_->max_write_size_);
200 :
201 929 : std::size_t const old_size = self_->data_.size();
202 929 : self_->data_.resize(old_size + n);
203 929 : buffer_copy(make_buffer(
204 929 : self_->data_.data() + old_size, n), buffers_, n);
205 :
206 929 : ec = self_->consume_match_();
207 929 : if(ec)
208 : {
209 2 : self_->data_.resize(old_size);
210 2 : return {ec, 0};
211 : }
212 :
213 927 : return {{}, n};
214 : }
215 : };
216 1194 : return awaitable{this, buffers};
217 : }
218 : };
219 :
220 : } // test
221 : } // capy
222 : } // boost
223 :
224 : #endif
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