Re: [RFC] NSE pack/unpack library

["Philip Pickering" <pgpickering () gmail com>]

2008/6/20 Brandon Enright <bmenrigh () ucsd edu>:
> > bin.unpack(bindata, template)
> > ... bindata is a string with the packed binary data
> > ... template is, again, the format string
> > --> returns the position where it stopped as first value and
> > the unpacked data values as the following return values
> > (the position can be used to subsequently fetch more data
> > by using it as a third parameter)
>
> If I'm to understand this we'll have to unpack in a loop rather than
> something like:
>
> local a, b, c, d
> (a, b, c, d) bin.unpack("C C C C", somestring)

you can still do

local a, b, c, d
_, a, b, c, d = bin.unpack(somestring, "C C C C")


but, for example, if your data begins with a short value for the
length of a following string you can do

pos, len = bin.unpack(somestring, "s")
_, newstring = bin.unpack(somestring, "A" .. len, pos)


Another thing I just realized is that bin.unpack's parameters are (data, format)
whereas perl's are (format, data). I guess I should adapt to Perl's way of
ordering it, because many people probably will be used to it (and I think it
doesn't really make a difference, which way round it is). It seems more
consistent, too, if the first parameter is the format string in both functions.


> It sure would be nice to be able to get a list back rather than having
> to do it in a loop.

Unpacking into a table could be an additional feature.


> I like all your ideas here and I think this will be very useful.

thanks,
Philip

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