ToolTalk procids and sessions

When a ToolTalk client calls tt_open() or tt_session_join(), the new procid or session is the default for the thread (and not the entire process as would be the for a non-multi-threaded ToolTalk client). A thread's default procid and session, before any calls to tt_open() or tt_session_join() are made, are initially the same as the defaults for the creator of the thread. In addition to changing the defaults with tt_open() or tt_session_join(), tt_thread_procid_set() and tt_thread_session_set() can be used to switch to other defaults created previously. The default procid and session values can be retrieved using tt_thread_procid() and tt_thread_session(). The thread-specific procid and session values are managed through the use of thread-specific storage. If no value has yet been created in the thread, the default value for the entire ToolTalk process is the fallback value.

It is possible for the values returned by tt_default_procid() and tt_thread_procid() (and similarly, tt_default_session() and tt_thread_session()) to be different at any given time for some thread. This is so because tt_default_procid_set() and tt_default_session_set() do not affect the default values for a thread. They only affect the default values for the entire ToolTalk process.

Using threads with ToolTalk enabled applications is a natural implementation technique for programs that switch procids and sessions. These programs might, at some point, want to easily determine which ToolTalk procid is associated with a ToolTalk session. This was difficult to do in previous versions of ToolTalk. tt_procid_session() has been provided to accomplish this. Although tt_procid_session()does not depend on threads, it is useful for applications that use threads with ToolTalk.