...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Read a complete message asynchronously.
template< class DynamicBuffer, class ReadHandler = net::default_completion_token_t< executor_type>> DEDUCED async_read( DynamicBuffer& buffer, ReadHandler&& handler = net::default_completion_token_t< executor_type >{});
This function is used to asynchronously read a complete message. This call always returns immediately. The asynchronous operation will continue until one of the following conditions is true:
error::closed
.
The algorithm, known as a composed asynchronous operation,
is implemented in terms of calls to the next layer's async_read_some
and async_write_some
functions.
The program must ensure that no other calls to read
, read_some
, async_read
, or async_read_some
are performed
until this operation completes. Received message data is appended to the
buffer. The functions got_binary
and got_text
may be used to query
the stream and determine the type of the last received message. Until the
operation completes, the implementation will read incoming control frames
and handle them automatically as follows:
control_callback
will be invoked
for each control frame.
error::closed
will be indicated.
Pong frames and close frames sent by the implementation while the read operation is outstanding do not prevent the application from also writing message data, sending pings, sending pongs, or sending close frames.
Name |
Description |
---|---|
|
A dynamic buffer to append message data to. |
|
The completion handler to invoke when the operation completes. The implementation takes ownership of the handler by performing a decay-copy. The equivalent function signature of the handler must be: void handler( error_code const& ec, // Result of operation std::size_t bytes_written // Number of bytes appended to buffer );
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
Invocation of the handler will be performed in a manner equivalent
to using |
This asynchronous operation supports cancellation for the following net::cancellation_type values:
net::cancellation_type::terminal
net::cancellation_type::total
total
cancellation succeeds
if the operation is suspended due to ongoing control operations such as
a ping/pong. terminal
cancellation
succeeds when supported by the underlying stream. terminal
cancellation leaves the stream in an undefined state, so that only closing
it is guaranteed to succeed.