Method download

src/SFML/Network/Sftp.cpp:1138–1248

///////////////////////////////////////////////////////

////////////////////////////////////////////////////////////
Sftp::Result Sftp::download(const std::filesystem::path&                                   remotePath,
                            const std::function<bool(const void* data, std::size_t size)>& callback,
                            std::uint64_t                                                  offset,
                            const TimeoutWithPredicate&                                    timeout)
{
    if (!callback)
        return Result(Result::Value::Error);

    LIBSSH2_SFTP_HANDLE* handle{};

    // Open the file for reading
    {
        const auto pathString = pathToUtf8(remotePath);
        const auto result     = m_impl->waitForOperationComplete(
            [&]
            {
                if (handle = libssh2_sftp_open_ex(m_impl->sftpSession.get(),
                                                  pathString.data(),
                                                  static_cast<unsigned int>(pathString.size()),
                                                  LIBSSH2_FXF_READ,
                                                  0,
                                                  LIBSSH2_SFTP_OPENFILE);
                    handle)
                    return LIBSSH2_ERROR_NONE;

                return libssh2_session_last_errno(m_impl->ssh2Session.get());
            },
            timeout);

        if (result == LIBSSH2_ERROR_EAGAIN)
            return Result(Result::Value::Timeout);

        if (!handle)
            return makeError(m_impl->ssh2Session.get(), m_impl->sftpSession.get());
    }

    // Seek to the offset if one was specified
    if (offset > 0)
        libssh2_sftp_seek64(handle, offset);

    // Read from the file
    {
        static constexpr auto bufferSizeStart = std::size_t{4 * 1024};
        static constexpr auto bufferSizeMax   = std::size_t{1024 * 1024};
        auto                  bufferSize      = bufferSizeStart;
        auto buffer = std::make_unique<char[]>(bufferSize); // NOLINT(cppcoreguidelines-avoid-c-arrays,modernize-avoid-c-arrays)

        while (true)
        {
            std::size_t length = bufferSize;
            auto*       ptr    = buffer.get();
            int         read{};
            std::size_t totalRead{};

            while (length > 0)
            {
                read = m_impl->waitForOperationComplete(
                    [&] { return static_cast<int>(libssh2_sftp_read(handle, ptr, length)); },