IOHandler(3I)						    InterViews Reference Manual 					     IOHandler(3I)

NAME

       IOHandler - read input, write output, or handle an I/O exception or timeout

SYNOPSIS

       #include <Dispatch/iohandler.h>

DESCRIPTION

       An iohandler reads data from a file descriptor, writes data to a file descriptor, handles an I/O exception on a file descriptor, or handles
       a timer's expiration.  Once the user has requested the dispatcher to attach an iohandler to a file descriptor or a  timer,  the	dispatcher
       will automatically notify the iohandler when the file descriptor's I/O condition changes or the timer expires.

       For convenience, the user can use a derived generic class (see IOCallback(3I)) to make the iohandler do nothing more than call an arbitrary
       object's member function.

PUBLIC OPERATIONS

       virtual int inputReady(int fd)
       virtual int outputReady(int fd)
       virtual int exceptionRaised(int fd)
	      The dispatcher will call one of these functions to notify an iohandler that it can read data from a file descriptor, write data to a
	      file  descriptor, or handle an I/O exception on a file descriptor.  The iohandler should perform the appropriate action and tell the
	      dispatcher what to do next.  A negative return value means that the iohandler encountered an error or it doesn't	want  to  read	or
	      write  anything  more.   The  dispatcher	will unlink the iohandler from its file descriptor automatically.  A positive return value
	      means that the iohandler didn't read or write everything that it could have.  The dispatcher will call the iohandler again in  round
	      robin  fashion  WITHOUT  checking  select, which means that the iohandler will be called again as soon as the rest of the iohandlers
	      have performed their actions.  A zero return value means that the iohandler finished reading or writing everything it was  able  to.
	      The dispatcher must check the descriptor's status with the select call before it can call the iohandler again.

       virtual void timerExpired(long sec, long usec)
	      The  dispatcher will call this function to notify an iohandler that a timer has expired.	For informational purposes, the parameters
	      give the current time in seconds and microseconds since midnight January 1, 1970.  If the iohandler wants to  reset  the	timer,	it
	      must tell the dispatcher to start another timer.

SEE ALSO

       Dispatcher(3I), IOCallback(3I)

InterViews							  9 January 1991						     IOHandler(3I)