...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
The boost::asio::use_future
special value provides first-class
support for returning a C++11 std::future
from an asynchronous
operation's initiating function.
To use boost::asio::use_future
, pass it to an asynchronous
operation instead of a normal completion handler. For example:
std::future<std::size_t> length = my_socket.async_read_some(my_buffer, boost::asio::use_future);
Where a handler signature has the form:
void handler(boost::system::error_code ec, result_type result);
the initiating function returns a std::future
templated on
result_type
. In the above example, this is std::size_t
.
If the asynchronous operation fails, the error_code
is converted
into a system_error
exception and passed back to the caller
through the future.
Where a handler signature has the form:
void handler(boost::system::error_code ec);
the initiating function returns std::future<void>
. As
above, an error is passed back in the future as a system_error
exception.