Re: parse_timespec function

[Michael Pattrick <mpattrick () rhinovirus org>]

On Mon, Apr 5, 2010 at 4:02 PM, David Fifield <david () bamsoftware com> wrote:
> On Fri, Apr 02, 2010 at 04:54:38PM -0700, Fyodor wrote:
> > On Fri, Apr 02, 2010 at 07:01:56PM -0400, Michael Pattrick wrote:
> > > > Other scripts take time arguments in seconds, not minutes. It's not the
> > > > best for this script but I'd like it if you make this script work that
> > > > way too. In the future we should have a standard function for parsing a
> > > > time specification like "60s" or "1m".
> > >
> > > I have implemented it to stay consistent with the new argument name,
> > > but I don't think it works well... No one would be running a fuzzer
> > > for less then one minute.
> >
> > Yeah, it will be better when we have a custom time parsing function
> > for NSE like David suggested.  We already have one for Nmap proper.
> > I've added it to docs/TODO.
> >
> > But for now, I think standardizing on seconds like you've done makes
> > sense.  While it may be slightly annnoying to type in 1200 rather than
> > 20 to run for 20 minutes, it beats having to look up the documentation
> > each time or to get it wrong.
>
> Here's a proposed function to go in stdnse.
>
> ---
> -- Parses a time duration specification, which is a number followed by a
> -- unit, and returns a number of seconds. The unit is optional and
> -- defaults to seconds. The possible units (case-insensitive) are
> -- * <code>s</code>: seconds,
> -- * <code>m</code>: minutes,
> -- * <code>h</code>: hours.
> -- In case of a parsing error, the function returns <code>nil</code>
> -- followed by an error message.
> --
> -- @usage
> -- parse_timespec("10") --> 10
> -- parse_timespec("10s") --> 10
> -- parse_timespec("10m") --> 600
> -- parse_timespec("10h") --> 3600
> -- parse_timespec("10z") --> nil, "Can't parse time specification \"10z\" (bad unit \"z\""
> --
> -- @param timespec A time specification string.
> -- @return A number of seconds, or <code>nil</code> followed by an error
> -- message.
> function parse_timespec(timespec)
>  local n, unit
>  local multiplier
>
>  n, unit = string.match(timespec, "^(%d+)(.*)$")
>  if not n then
>    return nil, string.format("Can't parse time specification \"%s\"", timespec)
>  end
>  n = tonumber(n)
>  assert(n)
>
>  unit = string.lower(unit)
>  if unit == "" or unit == "s" then
>    multiplier = 1
>  elseif unit == "m" then
>    multiplier = 60
>  elseif unit == "h" then
>    multiplier = 60 * 60
>  else
>    return nil, string.format("Can't parse time specification \"%s\" (bad unit \"%s\")", timespec, unit)
>  end
>
>  return n * multiplier
> end
>
> If this looks good, I'll commit it and change scripts to use it where
> appropriate.
>
> David Fifield

The following line:
-- parse_timespec("10h") --> 3600
Should probably be:
-- parse_timespec("10h") --> 36000

Other then that it looks good.

-M
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