tt_message_callback_add(3)

tt_message_callback_addC3LIBRARY FUNCTItt_message_callback_add(3)

NAME
     tt_message_callback_add - register	a callback function

SYNOPSIS
     #include <Tt/tt_c.h>

     Tt_status tt_message_callback_add(Tt_message m,
				       Tt_message_callback f);

DESCRIPTION
     The tt_message_callback_add() function registers a	 callback
     function	   to	  be	 automatically	   invoked     by
     tt_message_receive(3) whenever a reply or other state-change
     to	this message is	returned.

     The callback is defined in	 <Tt/tt_c.h>.	If  the	 callback
     returns  TT_CALLBACK_CONTINUE,  other callbacks will be run;
     if	   no	  callback     returns	   TT_CALLBACK_PROCESSED,
     tt_message_receive()  returns  the	message.  If the callback
     returns  TT_CALLBACK_PROCESSED,  no  further  callbacks  are
     invoked for this event; tt_message_receive() does not return
     the message.

     The m argument is the opaque handle for the message involved
     in	 this  operation.  The f argument is the message callback
     to	be run.

     The pattern handle	will be	NULL if	the message did	not match
     a	dynamic	 pattern.   This  is usually the case for message
     callbacks.

RETURN VALUE
     Upon successful  completion,  the	tt_message_callback_add()
     function  returns	the status of the operation as one of the
     following Tt_status values:

	TT_OK	The operation completed	successfully.

	TT_ERR_NOMP
		The ttsession(1) process is not	running	 and  the
		ToolTalk service cannot	restart	it.

	TT_ERR_POINTER
		The pointer passed does	not point to an	object of
		the correct type for this operation.

APPLICATION USAGE
     These callbacks are invoked from  tt_message_receive();  the
     program  must, therefore, call tt_message_receive() when the
     file descriptor returned by tt_fd() becomes active.

Unix System LaboratorLast change: 11 May 1994			1

tt_message_callback_addC3LIBRARY FUNCTItt_message_callback_add(3)

     The application can use tt_message_callback_add() to  create
     wrappers for ToolTalk messages.  For example, a library rou-
     tine can construct	a request, attach a callback to	the  mes-
     sage,  send  the message, and process the reply in	the call-
     back.  When the callback returns TT_CALLBACK_PROCESSED,  the
     message  reply is not returned to the main	program; the mes-
     sage and reply are, therefore, completely hidden.

SEE ALSO
     Tttt_c(5),	tt_message_receive(3).

Unix System LaboratorLast change: 11 May 1994			2