103 lines
4.3 KiB
Racket
103 lines
4.3 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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compute-patches
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compute-affected-pids)
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(require racket/set)
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(require racket/match)
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(require "route.rkt")
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(require "patch.rkt")
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(require "trace.rkt")
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(require "tset.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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) #:transparent)
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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 (matcher-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 (matcher-empty) (pattern->matcher #t ?))))
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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 (matcher-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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(let ((pids (compute-affected-pids old-routing-table delta)))
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(tset-remove (tset-add pids label) 'meta))) ;; TODO: removing meta is weird
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(values (for/list [(pid (tset->list affected-pids))]
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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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(and (not (meta-label? label))
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(drop-patch
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(compute-aggregate-patch delta label old-routing-table #:remove-meta? #t)))))
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(define (compute-affected-pids routing-table delta)
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(define cover (matcher-union (patch-added delta) (patch-removed delta)))
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(matcher-match-matcher cover
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(matcher-step routing-table struct:observe)
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#:seed (datum-tset)
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#:combiner (lambda (v1 v2 acc) (tset-union v2 acc))
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#:left-short (lambda (v r acc)
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(tset-union acc (success-value (matcher-step r EOS))))))
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(define (mux-route-message m body)
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(if (matcher-match-value (mux-routing-table m) body #f) ;; some other stream has declared body
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'()
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(tset->list (matcher-match-value (mux-routing-table m) (observe body) (datum-tset)))))
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(define (mux-interests-of m label)
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(hash-ref (mux-interest-table m) label (matcher-empty)))
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