Read part of a message asynchronously.
template< class DynamicBuffer, class ReadHandler> DEDUCED async_read_some( DynamicBuffer& buffer, std::size_t limit, ReadHandler&& handler);
This function is used to asynchronously read part of a message from the stream. The function call always returns immediately. The asynchronous operation will continue until one of the following is true:
This operation is implemented in terms of one or more calls to the next
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.
websocket::stream::got_text may be used to query
the stream and determine the type of the last received message. The function
websocket::stream::is_message_done may be called
to determine if the message received by the last read operation is complete.
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).
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.
An upper limit on the number of bytes this function will append into the buffer. If this value is zero, then a reasonable size will be chosen automatically.
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