我围绕 Boostless asio 编写了一个包装器来处理所有网络通信。大多数交换涉及在客户端和服务器之间来回发送多个数据包。我现在有一个问题，如果我嵌套对 asio 方法的调用，我最终会出现在方法中__throw_bad_function_call();
这是我的听众：
.hpp
/// \brief Socket object used to manage connections to the remote server.
struct listener : public std::enable_shared_from_this<listener> {
/// \brief Creates an instance of the object and opens a connection to the remote host.
/// \param[in] params Connection parameters.
/// \param[out] ec Errors returned by the OS.
explicit listener(const parameters ¶ms, std::error_code &ec) noexcept;
/// \brief Executes all queued handlers and resets the io_context for another run.
auto execute_handlers() noexcept -> void;
/// \brief Writes data to the socket.
/// \details Writes data to the socket and passes any errors to the callback.
/// \param[in] barray Byte array to send to the server.
/// \param[in] callback Method called when data has been written to the server.
auto write(packet barray, std::function<void(std::error_code ec, std::size_t length)> callback) noexcept -> void;
/// \brief Reads data from the socket.
/// \details Reads that present in the socket and passes the data as a single byte array to the callback.
/// \param[in] callback Method called when data has been written to the server.
auto read(std::function<void(std::error_code ec, packet barray)> callback) noexcept -> void;
private:
/// \brief Underlying OS socket.
std::unique_ptr<asio::generic::stream_protocol::socket> m_socket;
asio::io_context m_context;
asio::local::stream_protocol::endpoint m_endpoint;
/// \brief Connection parameters
parameters m_params;
/// \brief DNS resolver
asio::ip::tcp::resolver m_resolver;
/// \brief Buffer that holds data to be received from the socket. Reset and resized before each call to read().
packet m_buffer;
};
.cpp
listener::listener(const parameters ¶ms, std::error_code &ec) noexcept
: m_endpoint{params.domain_socket}, m_params{params}, m_resolver{m_context} {
#if !defined(_WIN32) && !defined(_WIN64)
if (!m_params.domain_socket.empty()) {
m_socket.reset(new asio::generic::stream_protocol::socket(m_context));
m_socket->connect(m_endpoint, ec);
if (ec) {
return;
}
m_socket->non_blocking(true);
return;
}
#endif
m_resolver.async_resolve(m_params.host, std::to_string(m_params.port),
[&](const std::error_code &error, asio::ip::tcp::resolver::results_type results) {
if (error) {
ec = error;
return;
}
//! \todo Add timeout to async_connect
for (const auto &endpoint : results) {
m_socket.reset(new asio::generic::stream_protocol::socket(m_context));
m_socket->async_connect(endpoint.endpoint(), [&](const std::error_code &err_c) {
if (err_c) {
ec = err_c;
return;
}
});
}
});
}
auto listener::execute_handlers() noexcept -> void {
const auto handlers = m_context.run();
m_context.restart();
}
auto listener::write(packet barray, std::function<void(std::error_code ec, std::size_t length)> callback) noexcept
-> void {
asio::async_write(*m_socket, asio::buffer(barray), callback);
}
auto listener::read(std::function<void(std::error_code ec, packet barray)> callback) noexcept -> void {
packet tmp;
tmp.resize(1);
asio::async_read(*m_socket, asio::buffer(tmp), asio::transfer_exactly(1),
[&](std::error_code ec, std::size_t size) {
if (!ec) {
const auto available = m_socket->available();
m_buffer.resize(available);
m_buffer.shrink_to_fit();
asio::async_read(*m_socket, asio::buffer(m_buffer), asio::transfer_all());
}
callback(ec, std::move(m_buffer));
});
}
然后我开始与远程服务器进行交换，但 lldb 告诉我我们失败了：
auto connection::do_connect(std::function<void(std::error_code ec, sql_state state)> callback) noexcept -> void {
m_listener = std::make_shared<listener>(m_params, ec);
m_listener->execute_handlers();
if (ec) {
callback(ec, state);
}
sql_state state;
const auto startup = write::startup(m_params);
m_listener->write(startup, [&](std::error_code ec, std::size_t length) {
if (ec) {
callback(ec, state);
}
m_listener->read([&](std::error_code ec, packet packet){});
});
m_listener->execute_handlers();
}
在 lldb 中运行此命令失败并显示以下跟踪：
Process 82736 launched: '/Users/ruihpacheco/Desktop/databaseclient/build_ninja/tests/integration/integration' (x86_64)
Process 82736 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=EXC_I386_GPFLT)
frame #0: 0x0000000100178118 integration`std::__1::function<void (std::__1::error_code, std::__1::vector<nonstd::byte, std::__1::allocator<nonstd::byte> >)>::operator(this=0x00007ffeefbfd780, __arg=(__val_ = 0, __cat_ = 0x00007fffa6cd6cd8), __arg=size=329)(std::__1::error_code, std::__1::vector<nonstd::byte, std::__1::allocator<nonstd::byte> >) const at functional:1913
1910 {
1911 if (__f_ == 0)
1912 __throw_bad_function_call();
-> 1913 return (*__f_)(_VSTD::forward<_ArgTypes>(__arg)...);
1914 }
1915
1916 #ifndef _LIBCPP_NO_RTTI
Target 0: (integration) stopped.
感觉应该可以了。。。