<h2>Packets</h2>

<verbatim>
;; Copyright 2006-2017, Matthew Welland.
;; 
;; This file is part of Pkts
;; 
;;     Pkts is free software: you can redistribute it and/or modify
;;     it under the terms of the GNU General Public License as published by
;;     the Free Software Foundation, either version 3 of the License, or
;;     (at your option) any later version.
;; 
;;     Pkts is distributed in the hope that it will be useful,
;;     but WITHOUT ANY WARRANTY; without even the implied warranty of
;;     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;     GNU General Public License for more details.
;; 
;;     You should have received a copy of the GNU General Public License
;;     along with Pkts.  If not, see <http://www.gnu.org/licenses/>.
;;

;; CARDS:
;;
;; A card is a line of text, the first two characters are a letter followed by a
;;   space. The letter is the card type.
;;
;; PKTS:
;;
;; A pkt is a sorted list of cards with a final card Z that contains the shar1 hash
;;   of all of the preceding cards.
;;
;; APKT:
;;
;;  An alist mapping card types to card data
;;      '((T . "pkttype")
;;        (a . "some content"))
;;
;; EPKT:
;;
;;  Extended packet using friendly keys. Must use a pktspec to convert to/from epkts
;;    '((ptype . "pkttype")
;;      (adata . "some content))
;;
;; DPKT:
;;
;; pkts pulled from the database have this format:
;;
;;((apkt (Z . "7de89c09ac024b3832c93e16cd78d11e2e28733b")     <= this is a the alist
;;       (t . "v1.63/tip/dev")
;;       (c . "QUICKPATT")
;;       (T . "runstart")
;;       (P . "354eeb67120a921e3e33155ecab1b522ac10b6bd")
;;       (D . "1488995096.0"))
;;  (id . 8)
;;  (group-id . 0)
;;  (uuid . "7de89c09ac024b3832c93e16cd78d11e2e28733b")
;;  (parent . "")
;;  (pkt-type . "runstart")
;;  (pkt . "D 1488995096.0\nP 354eeb67120a921e3e33155ecab1b522ac10b6bd\nT runstart\nc QUICKPATT\nt v1.63/tip/dev\nZ 7de89c09ac024b3832c93e16cd78d11e2e28733b"))
;;
;; pktspec is alist of alists mapping types and nicekeys to keys
;;
;; '((posting . ((title . t)
;;               (url   . u)
;;               (blurb . b)))
;;   (comment . ((comment . c)
;;               (score   . s))))

;; Reserved cards:
;;   P      : pkt parent
;;   R      : reference pkt containing mapping of short string -> sha1sum strings
;;   T      : pkt type
;;   D      : current time from (current-time), unless provided
;;   Z      : shar1 hash of the packet

;; Example usage:
;;
;; Create a pkt:
;;
;; (use pkts)
;; (define-values (uuid pkt)
;;     (alist->pkt
;;       '((fruit . "apple") (meat . "beef"))  ;; this is the data to convert
;;       '((foods (fruit . f) (meat . m)))     ;; this is the pkt spec
;;       ptype:
;;       'foods))
;;
;; Add to pkt queue:
;;
;; (define db (open-queue-db "/tmp/pkts" "pkts.db"))
;; (add-to-queue db pkt uuid 'foods #f 0) ;; no parent and use group_id of 0
;;
;; Retrieve the packet from the db and extract a value:
;;
;; (alist-ref
;;    'meat
;;    (dpkt->alist
;;         (car (get-dpkts db #f 0 #f))
;;        '((foods (fruit . f)
;;                 (meat . m)))))
;; => "beef"
;;
</verbatim>