...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 message asynchronously.
template< class DynamicBuffer, class ReadHandler> DEDUCED async_read( DynamicBuffer& buffer, ReadHandler&& handler);
This function is used to asynchronously read a complete message from the stream. The function call always returns immediately. The asynchronous operation will continue until one of the following is true:
websocket::closed
.
This operation is implemented in terms of one or more calls to the next
layer's async_read_some
and async_write_some
functions,
and is known as a composed operation. The program
must ensure that the stream performs no other reads until this operation
completes.
Received message data, if any, is appended to the input area of the buffer.
The functions websocket::stream::got_binary
and websocket::stream::got_text
may be used to query
the stream and determine the type of the last received message.
While this operation is active, the implementation will read incoming control frames and handle them automatically as follows:
websocket::stream::control_callback
will be invoked
for each control frame.
websocket::closed
will be indicated.
Because of the need to handle control frames, asynchronous read operations
can cause writes to take place. These writes are managed transparently;
callers can still have one active asynchronous read and asynchronous write
operation pending simultaneously (a user initiated call to websocket::stream::async_close
counts as a write).
Name |
Description |
---|---|
|
A dynamic buffer to hold the message data after any masking or decompression has been applied. This object must remain valid until the handler is called. |
|
Invoked when the operation completes. The handler may be moved or copied as needed. 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 |