Dispatcher(3I)						    InterViews Reference Manual 					    Dispatcher(3I)

NAME

       Dispatcher - wait on multiple file descriptors until a condition occurs

SYNOPSIS

       #include <Dispatch/dispatcher.h>

DESCRIPTION

       Conceptually, the dispatcher plays the role of detecting new data on multiple input file descriptors and dispatching the data to the appro-
       priate iohandlers.  The dispatcher also notifies iohandlers of expired timers.  Notification of either an I/O condition or an expired timer
       occurs  by  calling one of the iohandler's virtual functions (see IOHandler(3I)).  Since a program needs only one instance of Dispatcher, a
       static member function is provided to create that instance if necessary and return it.

PUBLIC OPERATIONS

       enum DispatcherMask { ReadMask, WriteMask, ExceptMask }
       virtual IOHandler* handler(int fd, DispatcherMask)
       virtual void link(int fd, DispatcherMask, IOHandler*)
       virtual void unlink(int fd)
	      Return a file descriptor's iohandler, link a file descriptor to an iohandler, or unlink a file descriptor from its iohandlers.   The
	      DispatcherMask  describes  the  I/O  condition that the iohandler is interested in, such as whether the file descriptor has new data
	      available for reading.  If the I/O condition occurs, the iohandler will be expected to read data from  the  file	descriptor,  write
	      data to the file descriptor, or handle the exception depending on the I/O condition.

       virtual void startTimer(long sec, long usec, IOHandler*)
       virtual void stopTimer(IOHandler*)
	      Attach an iohandler to a timer or remove a timer before it expires.  A timer expires after the given number of seconds and microsec-
	      onds have elapsed.  If a timer expires, the dispatcher will notify the attached iohandler.  Timers will not expire until the program
	      calls either variant of Dispatcher::dispatch.

       virtual void dispatch()
       virtual boolean dispatch(long& sec, long& usec)
	      With no arguments, block indefinitely until an I/O condition occurs or a timer expires and then notify the attached iohandler.  With
	      two arguments, block no longer than the given number of seconds and microseconds.  If both  numbers  are	zero,  the  function  will
	      return  immediately  after  checking  all file descriptors and timers.  The return value will be true if an I/O condition caused the
	      function to return and false if the function returned because a timer expired or it exceeded the given poll time.  The function will
	      decrease the given poll time by the amount of time it spent blocking.

       static Dispatcher& instance()
       static void instance(Dispatcher*)
	      With  no	arguments, create an instance of Dispatcher if it doesn't already exist and return it.	With an argument, set the instance
	      of Dispatcher that will be used throughout the program.

SEE ALSO

       select(2), IOHandler(3I)

InterViews							 21 December 1990						    Dispatcher(3I)