Hello,
I am trying to implement some new composed operations (like boost::asio::async_read) with asio.
However I am a bit concerned about thread-safety when the run-method of the used io_service object ist called from multiple threads and there are parallel read- and write operations on the same socket.
The composed operations look like this:
class io_port
{
public:
//Ctors and so on...
typedef boost::function completion_handler_t;
void async_read_data
( raw_buffer_t & buffer
, completion_handler_t const & handler)
{
//uses a composed operation itself...
boost::asio::async_read
( socket
, boost::asio::buffer(header)
, boost::bind
( &io_port::handle_header_received
, this
, boost::ref(buffer)
, handler
, boost::asio::placeholders::error) );
}
//first intermediate handler
void handle_header_received
( raw_buffer_t & data
, completion_handler_type const & handler
, boost::system::error_code const & error
{
if(error)
{
handler(error_t(error));
}
else
{
prepare_buffer(data, header.perparation_data()); //pseudo-code
//uses a composed operation itself...
boost::asio::async_read
( socket
, boost::asio::buffer(data)
, boost::bind
( &io_port::handle_data_received
, this
, boost::ref(buffer)
, handler
, boost::asio::placeholders::error) );
}
}
//second intermediate handler
void handle_data_received
( raw_buffer_t & data
, completion_handler_type const & handler
, boost::system::error_code const & error )
{
if(error)
{
handler(error_t(error));
}
else
{
handler(error_t());
}
}
void async_write_data
( raw_buffer_t const & buffer
, completion_handler_t const & handler)
{ ... } //quite similar to async_read_data
};
usage may be either
port.async_read
( buffer
, handler );
or
port.async_read
( buffer
, strand.wrap(handler) ); //how to forward this to asio::async_read?
If async_write_data is called and io_service::run is called from multiple threads, strands are should be necessary to avoid raced.
The question is: How do I support handlers wrapped in a strand and how do I get this strand forwarded to async_read?
As far as I understand this should be somehow possible by using asio_handler_invoke but the documentation is a bit too fuzzy on the topic for me to understand.
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