142 lines
5.7 KiB
Racket
142 lines
5.7 KiB
Racket
#lang racket/base
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;; General multiplexer.
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(provide meta-label?
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(except-out (struct-out mux) mux)
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(rename-out [mux <mux>] [make-mux mux])
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mux-add-stream
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mux-remove-stream
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mux-update-stream
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mux-route-message
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mux-interests-of
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;; mux-focus-event
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compute-patches
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compute-affected-pids
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pretty-print-mux)
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(require racket/set)
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(require racket/match)
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(require "trie.rkt")
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(require "patch.rkt")
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(require "tset.rkt")
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(require "pretty.rkt")
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;; A PID is a Nat.
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;; A Label is a PID or 'meta.
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;; Multiplexer private states
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(struct mux (next-pid ;; PID
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routing-table ;; (Matcherof (Setof Label))
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interest-table ;; (HashTable Label Matcher)
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)
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#:transparent
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#:methods gen:syndicate-pretty-printable
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[(define (syndicate-pretty-print m [p (current-output-port)])
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(pretty-print-mux m p))])
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define (meta-label? x) (eq? x 'meta))
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(define (make-mux)
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(mux 0 trie-empty (hash)))
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(define (mux-add-stream m initial-patch)
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(define new-pid (mux-next-pid m))
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(mux-update-stream (struct-copy mux m [next-pid (+ new-pid 1)])
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new-pid
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initial-patch))
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(define (mux-remove-stream m label)
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(mux-update-stream m label (patch trie-empty (pattern->trie '<mux-remove-stream> ?))))
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(define (mux-update-stream m label delta-orig)
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(define old-interests (mux-interests-of m label))
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(define old-routing-table (mux-routing-table m))
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(define delta (limit-patch (label-patch delta-orig (datum-tset label)) old-interests))
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(define new-interests (apply-patch old-interests delta))
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;; CONDITION at this point: delta has been labelled and limited to
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;; be minimal with respect to existing interests of its label.
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(define delta-aggregate (compute-aggregate-patch delta label old-routing-table))
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(define new-routing-table (apply-patch old-routing-table delta))
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(values (struct-copy mux m
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[routing-table new-routing-table]
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[interest-table (if (trie-empty? new-interests)
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(hash-remove (mux-interest-table m) label)
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(hash-set (mux-interest-table m) label new-interests))])
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label
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delta
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delta-aggregate))
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(define (compute-patches old-m new-m label delta delta-aggregate)
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(define old-routing-table (mux-routing-table old-m))
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(define new-routing-table (mux-routing-table new-m))
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(define affected-pids
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(tset-remove (tset-add (compute-affected-pids old-routing-table delta) label) 'meta))
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(define (entry-for pid)
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(cond [(equal? pid label)
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(define feedback
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(patch-union
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(patch (biased-intersection new-routing-table (patch-added delta))
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(biased-intersection old-routing-table (patch-removed delta)))
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(patch (biased-intersection (patch-added delta-aggregate)
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(mux-interests-of new-m label))
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(biased-intersection (patch-removed delta-aggregate)
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(mux-interests-of old-m label)))))
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(cons label feedback)]
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[else
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(cons pid (view-patch delta-aggregate (mux-interests-of old-m pid)))]))
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(values (for/list [(pid (tset->list affected-pids))]
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(entry-for pid))
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(cdr (entry-for 'meta))))
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(define (compute-affected-pids routing-table delta)
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(define cover (trie-union (patch-added delta) (patch-removed delta)))
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(trie-match-trie cover
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(trie-step routing-table observe-parenthesis)
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#:seed datum-tset-empty
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#:combiner (lambda (v1 v2 acc) (tset-union v2 acc))))
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(define (mux-route-message m body)
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(if (trie-lookup (mux-routing-table m) body #f #:wildcard-union (lambda (a b) (or a b)))
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;; some other stream has declared body
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(values '() #f)
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(let ((pids (trie-lookup (mux-routing-table m)
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(observe body)
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datum-tset-empty
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#:wildcard-union tset-union)))
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(values (tset->list (tset-remove pids 'meta))
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(tset-member? pids 'meta)))))
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(define (mux-interests-of m label)
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(hash-ref (mux-interest-table m) label trie-empty))
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;; There's a problem with mux-focus-event in most circumstances: often
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;; you will want to focus incoming events with respect to some
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;; locally-stored memory of interests. But that local memory may be
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;; *ahead* of the incoming event stream! There's the round-trip
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;; latency between the actor and the dataspaces where patch actions
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;; are applied. This could lead to unwanted discarding of retractions,
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;; and even of assertions in cases of quick pulses of interest.
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;;
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;; ;; Mux Label Event -> (Option Event)
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;; (define (mux-focus-event m label e)
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;; (define interests (mux-interests-of m label))
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;; (match e
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;; [(patch added removed)
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;; (define p (patch (biased-intersection added interests)
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;; (biased-intersection removed interests)))
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;; (and (patch-non-empty? p) p)]
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;; [(message body)
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;; (and (trie-lookup interests (observe body) #f) e)]))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define (pretty-print-mux m [p (current-output-port)])
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(match-define (mux next-pid routing-table interest-table) m)
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(fprintf p "MUX:\n")
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(fprintf p " - ~a labelled entities with claims\n" (hash-count interest-table))
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(fprintf p " - next label: ~a\n" next-pid)
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(fprintf p " - routing-table:\n")
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(display (indented-port-output 3 (lambda (p) (pretty-print-trie routing-table p))) p)
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(newline p))
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