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Updated: Thursday, June 13, 2019
 
 

tt_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

ToolTalk Functions                                  tt_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 mes-
       sage.  If the callback returns TT_CALLBACK_PROCESSED, no further  call-
       backs  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 cor-
                  rect 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.

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


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------+
       |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
       +---------------+------------------+
       |Availability   | library/tooltalk |
       +---------------+------------------+
       |Stability      | Committed        |
       +---------------+------------------+
SEE ALSO
       tt_c(5), tt_message_receive(3).




ToolTalk 1.3                     1 March 1996
                                                    tt_message_callback_add(3)