%
% (c) The AQUA Project, Glasgow University, 1995
%
%************************************************************************
%*                                                                      *
\section[Itimer.lc]{Interval Timer}
%*									*
%************************************************************************

The interval timer is used for profiling and for context switching in the
threaded build.  Though POSIX 1003.4 includes a standard interface for
such things, no one really seems to be implementing them yet.  Even 
Solaris 2.3 only seems to provide support for @CLOCK_REAL@, whereas we're
keen on getting access to @CLOCK_VIRTUAL@.

Hence, we use the old-fashioned @setitimer@ that just about everyone seems
to support.  So much for standards.

\begin{code}

#if defined(PROFILING) || defined(CONCURRENT)

# include "platform.h"

# define NON_POSIX_SOURCE

# include "rtsdefs.h"

/* As recommended in the autoconf manual */
# ifdef TIME_WITH_SYS_TIME
#  include <sys/time.h>
#  include <time.h>
# else
#  ifdef HAVE_SYS_TIME_H
#   include <sys/time.h>
#  else
#   include <time.h>
#  endif
# endif

int
initialize_virtual_timer(ms)
int ms;
{
# ifndef HAVE_SETITIMER
    fprintf(stderr, "No virtual timer on this system\n");
    return -1;
# else
    struct itimerval it;

    it.it_value.tv_sec = ms / 1000;
    it.it_value.tv_usec = 1000 * (ms - (1000 * it.it_value.tv_sec));
    it.it_interval = it.it_value;
    return (setitimer(ITIMER_VIRTUAL, &it, NULL));
# endif
}

# if 0
/* This is a potential POSIX version */
int
initialize_virtual_timer(ms)
int ms;
{
    struct sigevent se;
    struct itimerspec it;
    timer_t tid;

    se.sigev_notify = SIGEV_SIGNAL;
    se.sigev_signo = SIGVTALRM;
    se.sigev_value.sival_int = SIGVTALRM;
    if (timer_create(CLOCK_VIRTUAL, &se, &tid)) {
	fprintf(stderr, "Can't create virtual timer.\n");
	EXIT(EXIT_FAILURE);
    }
    it.it_value.tv_sec = ms / 1000;
    it.it_value.tv_nsec = 1000000 * (ms - 1000 * it.it_value.tv_sec);
    it.it_interval = it.it_value;
    timer_settime(tid, TIMER_RELTIME, &it, NULL);
}
# endif

#endif	/* PROFILING || CONCURRENT */

\end{code}