"Tangence::Stream" - base class for "Tangence" stream-handling mixins

       Paul Evans <leonerd@leonerd.org.uk>

perl v5.40.0                                       2024-09-13                              Tangence::Stream(3pm)

       This module provides a base for Tangence::Client and Tangence::Server.  It is not intended to be used
       directly by "Tangence" implementation code.

       It provides the basic layer of message serialisation, deserialisation, and dispatching to methods that
       would handle the messages. Higher level classes are used to wrap this functionality, and provide
       implementations of methods to handle the messages received.

       When a message is received, it will be passed to a method whose name depends on the code of message
       received. The name will be "handle_request_", followed by the name of the message code, in uppercase; for
       example "handle_request_CALL".

       "Tangence::Stream" - base class for "Tangence" stream-handling mixins

       The following methods are provided by this mixin.

   tangence_closed
          $stream->tangence_closed;

       Informs the object that the underlying connection has now been closed, and any attachments to
       "Tangence::Object" or "Tangence::ObjectProxy" instances should now be dropped.

   tangence_readfrom
          $stream->tangence_readfrom( $buffer );

       Informs the object that more data has been read from the underlying connection stream. Whole messages
       will be removed from the beginning of the $buffer, which should be passed as a direct scalar (because it
       will be modified). This method will invoke the required "handle_request_*" methods. Any bytes remaining
       that form the start of a partial message will be left in the buffer.

   request
          $stream->request( %args );

       Serialises a message object to pass to the "tangence_write" method, then enqueues a response handler to
       be invoked when a reply arrives. Takes the following named arguments:

       request => Tangence::Message
               The message body

       on_response => CODE
               CODE  reference to the callback to be invoked when a response to the message is received. It will
               be passed the response message:

                  $on_response->( $message );

   request(non-void)
          $response = await $stream->request( request => $request );

       When called in non-void context, this method returns a Future that will yield the  response  instead.  In
       this case it should not be given an "on_response" callback.

       In  this form, a "MSG_ERROR" response will automatically turn into a failed Future; the subsequent "then"
       or "on_done" code will not have to handle this case.

   respond
          $stream->respond( $token, $message );

       Serialises a message object to be sent to the "tangence_write" method. The $token value that  was  passed
       to  the  "handle_request_" method ensures that it is sent at the correct position in the stream, to allow
       the peer to pair it with the corresponding request.

   minor_version
          $ver = $stream->minor_version;

       Returns the minor version negotiated by the "MSG_INIT" / "MSG_INITED" initial message handshake.

       The following methods are required to be implemented by some class using this mixin.

   tangence_write
          $stream->tangence_write( $data );

       Write bytes of data to the connected peer. $data will be a plain perl string.

   handle_request_$CODE
          $stream->handle_request_$CODE( $token, $message );

       Invoked on receipt of a given message code. $token will be some opaque perl scalar value, and $message
       will be an instance of Tangence::Message.

       The value of the token has no particular meaning, other than to be passed to the "respond" method.