# PR_IntervalNow

Returns the value of NSPR's free-running interval timer.

## Syntax

```{code}
#include <prinrval.h>

PRIntervalTime PR_IntervalNow(void);
```

### Returns

A {ref}`PRIntervalTime` object.

## Description

You can use the value returned by `PR_IntervalNow()` to establish
epochs and to determine intervals (that is, compute the difference
between two times). `PR_IntervalNow()` is both very efficient and
nonblocking, so it is appropriate to use (for example) while holding a
mutex.

The most common use for `PR_IntervalNow()` is to establish an epoch
and test for the expiration of intervals. In this case, you typically
call `PR_IntervalNow()` in a sequence that looks like this:

```{code}
PRUint32 interval = ... ; // milliseconds
// ...
PRStatus rv;
PRIntervalTime epoch = PR_IntervalNow();
PR_Lock(data->mutex);
while (!EvaluateData(data))  /* wait until condition is met */
{
    PRUint32 delta = PR_IntervalToMilliseconds(PR_IntervalNow() - epoch);
    if (delta > interval) break;  /* timeout */
    rv = PR_Wait(data->condition, PR_MillisecondsToInterval(interval - delta));
    if (PR_FAILURE == rv) break;  /* likely an interrupt */
}
PR_Unlock(data->mutex);
```