tt_message_callback_add(3) ToolTalk Functions tt_message_callback_add(3)NAMEtt_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.
SEE ALSOtt_c(5), tt_message_receive(3).
ToolTalk 1.3 1 March 1996 tt_message_callback_add(3)
