Page 183 - DCAP507_SYSTEM_SOFTWARE

Unit 11: Programming Languages Concept (II)

This shows that the handler must not be called directly from within the initiating function, Notes
although the asynchronous operation completes instantly.
A bound completion handler is a handler object that includes a copy of a user-supplied handler,
where the user-supplied handler accepts one or more arguments. The bound completion handler
does not accept any arguments, and includes values to be passed as arguments to the user-
supplied handler. The bound completion handler forwards the handler_allocate(),
handler_deallocate(), and handler_invoke() calls to the analogous functions for the user-supplied
handler. A bound completion handler fulfills the requirements for a completion handler.

Example: A bound completion handler for a ReadHandler may be executed as follows:
template<class ReadHandler>
struct bound_read_handler
{

bound_read_handler(ReadHandler handler, const error_code& ec, size_t s)
: handler_(handler), ec_(ec), s_(s)
{
}

void operator()()
{
handler_(ec_, s_);

}

ReadHandler handler_;
const error_code ec_;

const size_t s_;
};

template<class ReadHandler>

void* asio_handler_allocate(size_t size,
bound_read_handler<ReadHandler>* this_handler)
{
using namespace boost::asio;

return asio_handler_allocate(size, &this_handler->handler_);
}

template<class ReadHandler>

void asio_handler_deallocate(void* pointer, std::size_t size,

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