/*
   clock.c

   simple code to provide a simulated clock interrupt, and routines
   for manipulating them.

   Winter 1996  Tian Lim

   4/6/96 moved atomic_test_and_set to assembly so the interrupt
   handler can restart it.

   4/7/96 renamed functions.

   4/21/96 switch to sigsetmask for enabling/disabling.  not
   necessarily good for threads that depend on lack of signals.

   */
#include "clock.h"
#include <stdio.h>

/* interrupts flag */
int		interrupts = 0;


/* global handle to the user's interrupt service routine */
static ClockHandler	interruptHandler;

/*
   this routine simulates a periodic clock tick.  every PERIOD
   microseconds it will be called. if interrupts are enabled, it will
   call your interrupt service routine
   */
void	clock_tick(int sig, int code, struct sigcontext*scp)
{
    if (interrupts==ENABLED) /* no longer necessary, but.... */
    {
	interruptHandler();
    }else 
    {
    }
    
}


void	enable_interrupts()
{
    interrupts = ENABLED;
    sigsetmask(0);
}


void 	disable_interrupts()
{
    interrupts = DISABLED;
    sigsetmask(sigmask(SIGALRM));
}


/* setup the interval timer and install interrupt handler.  After this
   routine is called, and after you enable_interrupts(), clock
   interrupts will begin to be sent.  They will call the handler
   function h specified by the caller. */

void	minithread_clock_init(ClockHandler h)
{
    struct itimerval	it, temp;

    interruptHandler = h;
    signal (SIGALRM, (ClockHandler)&clock_tick);
    
    it.it_interval.tv_sec = 0;
    it.it_interval.tv_usec = PERIOD;
    it.it_value.tv_sec = 0;
    it.it_value.tv_usec = PERIOD;
    disable_interrupts();
    setitimer(ITIMER_REAL, &it, &temp);
}