Re: A sleep function for NSE

[David Fifield <david () bamsoftware com>]

On Fri, Feb 20, 2009 at 09:26:07PM +0000, jah wrote:
> On 20/02/2009 18:55, David Fifield wrote:
> > A function called "sleep" normally takes an argument in seconds, even if
> > it only provides integer precision. So if the function changes to take
> > milliseconds its name has to change too. In the name of consistency, I
> > think there are only two choices: sleep taking a floating-point number
> > of seconds, or sleep_ms taking an integer number of milliseconds.
> >
> > My preference would be to have sleep take floating-point seconds, and to
> > change nmap.clock_ms and nmap.set_timeout to deal in seconds also. The
> > settimeout in Python does it in seconds:
> >
> > http://docs.python.org/library/socket.html#socket.socket.settimeout
> >
> > Furthermore, clock_ms should be renamed "time" because it is more like
> > the time function in C or os.time in Lua (seconds since 1970) than it is
> > the C clock function (time since some arbitrary point in arbitrary
> > units). clock_ms is doubly frustrating because it uses gettimeofday,
> > which provides microsecond precision, then purposely degrades the result
> > to return milliseconds.
> >
> > It may be too late for nmap.set_timeout because that would be an
> > incompatible change. nmap.clock_ms is easier because it is currently
> > hardly used and its name should change anyway. Any thoughts?
>
> Yeah, tricky.  As you (and Arturo) point out, sleep() normally takes
> seconds and it would be daft to stray from the norm without compelling
> reasons to do so.  If it's a lot of work to change set_timeout to
> seconds then we probably shouldn't - it's only a small detail after all
> and the function is well documented and probably fixed in people's minds
> by now.

I agree, set_timeout is just a detail.

> I agree with the name change for clock_ms, but are you suggesting
> changing it to accept seconds or to return microseconds?   It might be
> useful to have a fine-grained measurement of time - Doug's Qscan
> implemented as a script springs to mind.

Return seconds, as a floating-point number. Again I'm thinking of how it
works in Python:

$ python -c "import time; print '%.6f' % time.time()"
1235165681.158787

Maybe I didn't make it clear, but stdnse.sleep takes fractional seconds
too: stdnse.sleep(0.005) sleeps for 5 ms. Implementing a millisecond
sleep function over it is trivial: function(ms) stdnse.sleep(ms / 1000) end.

David

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