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//
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//
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// Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
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// Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
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//
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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//
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// Official repository: https://github.com/cppalliance/capy
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// Official repository: https://github.com/cppalliance/capy
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//
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//
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#ifndef BOOST_CAPY_TEST_WRITE_STREAM_HPP
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#ifndef BOOST_CAPY_TEST_WRITE_STREAM_HPP
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#define BOOST_CAPY_TEST_WRITE_STREAM_HPP
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#define BOOST_CAPY_TEST_WRITE_STREAM_HPP
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#include <boost/capy/detail/config.hpp>
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#include <boost/capy/detail/config.hpp>
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#include <boost/capy/buffers.hpp>
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#include <boost/capy/buffers.hpp>
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#include <boost/capy/buffers/buffer_copy.hpp>
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#include <boost/capy/buffers/buffer_copy.hpp>
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#include <boost/capy/buffers/make_buffer.hpp>
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#include <boost/capy/buffers/make_buffer.hpp>
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#include <boost/capy/coro.hpp>
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#include <boost/capy/coro.hpp>
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#include <boost/capy/ex/executor_ref.hpp>
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#include <boost/capy/ex/executor_ref.hpp>
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#include <boost/capy/io_result.hpp>
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#include <boost/capy/io_result.hpp>
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#include <boost/capy/error.hpp>
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#include <boost/capy/error.hpp>
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#include <boost/capy/test/fuse.hpp>
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#include <boost/capy/test/fuse.hpp>
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#include <algorithm>
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#include <algorithm>
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#include <stop_token>
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#include <stop_token>
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#include <string>
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#include <string>
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#include <string_view>
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#include <string_view>
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namespace boost {
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namespace boost {
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namespace capy {
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namespace capy {
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namespace test {
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namespace test {
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/** A mock stream for testing write operations.
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/** A mock stream for testing write operations.
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    Use this to verify code that performs writes without needing
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    Use this to verify code that performs writes without needing
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    real I/O. Call @ref write_some to write data, then @ref str
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    real I/O. Call @ref write_some to write data, then @ref str
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    or @ref data to retrieve what was written. The associated
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    or @ref data to retrieve what was written. The associated
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    @ref fuse enables error injection at controlled points. An
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    @ref fuse enables error injection at controlled points. An
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    optional `max_write_size` constructor parameter limits bytes
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    optional `max_write_size` constructor parameter limits bytes
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    per write to simulate chunked delivery.
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    per write to simulate chunked delivery.
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    @par Thread Safety
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    @par Thread Safety
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    Not thread-safe.
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    Not thread-safe.
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    @par Example
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    @par Example
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    @code
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    @code
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    fuse f;
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    fuse f;
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    write_stream ws( f );
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    write_stream ws( f );
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    auto r = f.armed( [&]( fuse& ) -> task<void> {
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    auto r = f.armed( [&]( fuse& ) -> task<void> {
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        auto [ec, n] = co_await ws.write_some(
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        auto [ec, n] = co_await ws.write_some(
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            const_buffer( "Hello", 5 ) );
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            const_buffer( "Hello", 5 ) );
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        if( ec )
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        if( ec )
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            co_return;
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            co_return;
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        // ws.str() returns "Hello"
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        // ws.str() returns "Hello"
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    } );
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    } );
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    @endcode
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    @endcode
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    @see fuse
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    @see fuse
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*/
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*/
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class write_stream
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class write_stream
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{
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{
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    fuse* f_;
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    fuse* f_;
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    std::string data_;
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    std::string data_;
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    std::string expect_;
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    std::string expect_;
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    std::size_t max_write_size_;
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    std::size_t max_write_size_;
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    std::error_code
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    std::error_code
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    consume_match_() noexcept
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    consume_match_() noexcept
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    {
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    {
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        if(data_.empty() || expect_.empty())
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        if(data_.empty() || expect_.empty())
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            return {};
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            return {};
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        std::size_t const n = (std::min)(data_.size(), expect_.size());
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        std::size_t const n = (std::min)(data_.size(), expect_.size());
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        if(std::string_view(data_.data(), n) !=
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        if(std::string_view(data_.data(), n) !=
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            std::string_view(expect_.data(), n))
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            std::string_view(expect_.data(), n))
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            return error::test_failure;
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            return error::test_failure;
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        data_.erase(0, n);
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        data_.erase(0, n);
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        expect_.erase(0, n);
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        expect_.erase(0, n);
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        return {};
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        return {};
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    }
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    }
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public:
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public:
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    /** Construct a write stream.
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    /** Construct a write stream.
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        @param f The fuse used to inject errors during writes.
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        @param f The fuse used to inject errors during writes.
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        @param max_write_size Maximum bytes transferred per write.
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        @param max_write_size Maximum bytes transferred per write.
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        Use to simulate chunked network delivery.
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        Use to simulate chunked network delivery.
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    */
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    */
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    explicit write_stream(
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    explicit write_stream(
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        fuse& f,
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        fuse& f,
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        std::size_t max_write_size = std::size_t(-1)) noexcept
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        std::size_t max_write_size = std::size_t(-1)) noexcept
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        : f_(&f)
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        : f_(&f)
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        , max_write_size_(max_write_size)
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        , max_write_size_(max_write_size)
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    {
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    {
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    }
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    }
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    /// Return the written data as a string view.
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    /// Return the written data as a string view.
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    std::string_view
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    std::string_view
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    data() const noexcept
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    data() const noexcept
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    {
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    {
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        return data_;
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        return data_;
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    }
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    }
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    /** Set the expected data for subsequent writes.
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    /** Set the expected data for subsequent writes.
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        Stores the expected data and immediately tries to match
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        Stores the expected data and immediately tries to match
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        against any data already written. Matched data is consumed
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        against any data already written. Matched data is consumed
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        from both buffers.
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        from both buffers.
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        @param sv The expected data.
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        @param sv The expected data.
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        @return An error if existing data does not match.
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        @return An error if existing data does not match.
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    */
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    */
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    std::error_code
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    std::error_code
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    expect(std::string_view sv)
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    expect(std::string_view sv)
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    {
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    {
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        expect_.assign(sv);
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        expect_.assign(sv);
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        return consume_match_();
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        return consume_match_();
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    }
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    }
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    /// Return the number of bytes written.
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    /// Return the number of bytes written.
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    std::size_t
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    std::size_t
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    size() const noexcept
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    size() const noexcept
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    {
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    {
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        return data_.size();
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        return data_.size();
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    }
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    }
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    /** Asynchronously write data to the stream.
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    /** Asynchronously write data to the stream.
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        Transfers up to `buffer_size( buffers )` bytes from the provided
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        Transfers up to `buffer_size( buffers )` bytes from the provided
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        const buffer sequence to the internal buffer. Before every write,
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        const buffer sequence to the internal buffer. Before every write,
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        the attached @ref fuse is consulted to possibly inject an error
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        the attached @ref fuse is consulted to possibly inject an error
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        for testing fault scenarios. The returned `std::size_t` is the
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        for testing fault scenarios. The returned `std::size_t` is the
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        number of bytes transferred.
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        number of bytes transferred.
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        @par Effects
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        @par Effects
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        On success, appends the written bytes to the internal buffer.
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        On success, appends the written bytes to the internal buffer.
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        If an error is injected by the fuse, the internal buffer remains
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        If an error is injected by the fuse, the internal buffer remains
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        unchanged.
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        unchanged.
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        @par Exception Safety
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        @par Exception Safety
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        No-throw guarantee.
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        No-throw guarantee.
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        @param buffers The const buffer sequence containing data to write.
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        @param buffers The const buffer sequence containing data to write.
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        @return An awaitable yielding `(error_code,std::size_t)`.
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        @return An awaitable yielding `(error_code,std::size_t)`.
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        @see fuse
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        @see fuse
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    */
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    */
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    template<ConstBufferSequence CB>
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    template<ConstBufferSequence CB>
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    auto
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    auto
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    write_some(CB buffers)
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    write_some(CB buffers)
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    {
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    {
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        struct awaitable
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        struct awaitable
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        {
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        {
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            write_stream* self_;
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            write_stream* self_;
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            CB buffers_;
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            CB buffers_;
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            bool await_ready() const noexcept { return true; }
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            bool await_ready() const noexcept { return true; }
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            // This method is required to satisfy Capy's IoAwaitable concept,
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            // This method is required to satisfy Capy's IoAwaitable concept,
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            // but is never called because await_ready() returns true.
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            // but is never called because await_ready() returns true.
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            //
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            //
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            // Capy uses a two-layer awaitable system: the promise's
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            // Capy uses a two-layer awaitable system: the promise's
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            // await_transform wraps awaitables in a transform_awaiter whose
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            // await_transform wraps awaitables in a transform_awaiter whose
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            // standard await_suspend(coroutine_handle) calls this custom
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            // standard await_suspend(coroutine_handle) calls this custom
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            // 3-argument overload, passing the executor and stop_token from
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            // 3-argument overload, passing the executor and stop_token from
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            // the coroutine's context. For synchronous test awaitables like
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            // the coroutine's context. For synchronous test awaitables like
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            // this one, the coroutine never suspends, so this is not invoked.
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            // this one, the coroutine never suspends, so this is not invoked.
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            // The signature exists to allow the same awaitable type to work
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            // The signature exists to allow the same awaitable type to work
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            // with both synchronous (test) and asynchronous (real I/O) code.
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            // with both synchronous (test) and asynchronous (real I/O) code.
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            void await_suspend(
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            void await_suspend(
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                coro,
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                coro,
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                executor_ref,
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                executor_ref,
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                std::stop_token) const noexcept
175   
                std::stop_token) const noexcept
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            {
176   
            {
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            }
177   
            }
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179   
            io_result<std::size_t>
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            io_result<std::size_t>
180   
            await_resume()
180   
            await_resume()
181   
            {
181   
            {
182   
                auto ec = self_->f_->maybe_fail();
182   
                auto ec = self_->f_->maybe_fail();
183   
                if(ec)
183   
                if(ec)
184   
                    return {ec, 0};
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                    return {ec, 0};
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186   
                std::size_t n = buffer_size(buffers_);
186   
                std::size_t n = buffer_size(buffers_);
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                n = (std::min)(n, self_->max_write_size_);
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                n = (std::min)(n, self_->max_write_size_);
188   
                if(n == 0)
188   
                if(n == 0)
189   
                    return {{}, 0};
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                    return {{}, 0};
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191   
                std::size_t const old_size = self_->data_.size();
191   
                std::size_t const old_size = self_->data_.size();
192   
                self_->data_.resize(old_size + n);
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                self_->data_.resize(old_size + n);
193   
                buffer_copy(make_buffer(
193   
                buffer_copy(make_buffer(
194   
                    self_->data_.data() + old_size, n), buffers_, n);
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                    self_->data_.data() + old_size, n), buffers_, n);
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                ec = self_->consume_match_();
196   
                ec = self_->consume_match_();
197   
                if(ec)
197   
                if(ec)
198   
                    return {ec, n};
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                    return {ec, n};
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                return {{}, n};
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                return {{}, n};
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            }
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            }
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        };
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        };
203   
        return awaitable{this, buffers};
203   
        return awaitable{this, buffers};
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    }
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    }
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};
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};
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} // test
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} // test
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} // capy
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} // capy
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} // boost
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} // boost
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#endif
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#endif