tt_message_callback_add(library call) tt_message_callback_add(library call)
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 - Tttt_c(5). If the callback
returns TT_CALLBACK_CONTINUE, other callbacks will be run; if no call‐
back 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 ser‐
vice 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.
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 ALSO
Tt/tt_c.h - Tttt_c(5), tt_message_receive(3).
tt_message_callback_add(library call)
