tt_message_callback_add - register a callback function
#include <Tt/tt_c.h> Tt_status tt_message_callback_add(Tt_message m, Tt_message_callback f);
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)