• At the end of the header, it calls Hook using call(Hook, header, Stream), where Stream is a stream holding the buffered header.
• If the stream is closed, it calls Hook using call(Hook, data, Stream), where Stream holds the buffered data.

The stream calls Hook, adding the event and CGIStream to the closure. Defined events are:

header

Called if the header is complete. Typically it uses cgi_property/2 to extract the collected header and combines these with the request and policies to decide on encoding, transfer-encoding, connection parameters and the complete header (as a Prolog term). Typically it uses cgi_set/2 to associate these with the stream.

send_header

Called if the HTTP header must be sent. This is immediately after setting the transfer encoding to chunked or when the CGI stream is closed. Typically it requests the current header, optionally the content-length and sends the header to the original (client) stream.

close

Called from close/1 on the CGI stream after everything is complete.

The predicates cgi_property/2 and cgi_set/2 can be used to control the stream and store status info. Terms are stored as Prolog records and can thus be transferred between threads.