After this is decoded, I want the the payload, and it'd be nice to have the
length too but not necessary.
Described in clojure instead of prose:
(defn get-payload-from-recursive-header-frame
[[hlenlen & raw-bytes]]
(let [hlen (apply + (take hlenlen raw-bytes))]
(drop hlenlen raw-bytes)))
Alternately, if I wanted to try to preserve the headers too:
(defn get-payload-from-recursive-header-frame-with-intermediate
[[hlenlen & raw-bytes]]
(let [hlens (take hlenlen raw-bytes)
hlen (apply + hlens)]
{:header-length hlenlen
:segment-lengths hlens
:payload (drop hlenlen raw-bytes)}))
Assuming "raw-bytes" is the whole packet including the header. In fact, I
tested the above on some sample data and confirmed it works... without gloss.
I'll bet there's a place where I could just slot in one of the above functions
within the gloss framework and it'd work, but I have not been able to figure
out exactly where.
-ken
--
-----
On Fri, Oct 10, 2014 at 10:32:59AM -0700, john walker wrote:
> What information do you want after this is decoded? Do you want the sum of
> byte0 ... byten, as well as the actual payload? Do you also want the
> header-length?
>
> On Thursday, October 9, 2014 11:34:59 PM UTC-7, Ken Restivo wrote:
> >
> > I'm playing around with Gloss, trying to decode a packet, part of which
> > has the following nested struture:
> >
> > header-length (1 byte, value n)
> > byte0 ... byten (count defined by that header-length byte)
> > actual payload (length of which is the sum of the values of the
> > above bytes)
> >
> > So instead of a fixed-size value (uint16, uint32, uint64, etc) defining
> > the size of the payload, there's a variable-length list of bytes (up to
> > 255), which has to be summed, to determine the length of the payload.
> >
> > Pretty easy to do imperatively, but I got lost in the dense forest of
> > gloss's abstractions, and couldn't figure out if it makes sense to try to
> > handle a case like this with it.
> >
> > -ken
> >
>
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