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Meme up radix tree

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xenia 2020-01-31 21:19:55 -05:00
parent d7d6f2bdfc
commit 0127f57230
1 changed files with 65 additions and 54 deletions
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radix-tree.rkt
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@ -1,89 +1,100 @@
#lang racket
(require data/bit-vector)
(require "iputil.rkt")
(provide make-rt rt-update! rt-lookup rt-dump)
(struct rt-node [edge0 edge1 data] #:transparent #:mutable)
(struct rt-edge [label target] #:transparent)
(define empty-node-data (gensym 'WATERDRINKERS))
(define (make-rt)
(rt-node #f #f #f))
(rt-node #f #f empty-node-data))
;; Helper functions for rt-node struct access based on whether the edge is 1 or 0
(define (rt-getter bit) (if bit rt-node-edge1 rt-node-edge0))
(define (rt-setter bit) (if bit set-rt-node-edge1! set-rt-node-edge0!))
;; Bit vector functions but short
(define bv-ref bit-vector-ref)
(define bv-len bit-vector-length)
(define bv-copy bit-vector-copy)
(define bv bit-vector)
(define (bl-common-len bl1 bl2)
(for/sum ([b1 (in-list bl1)]
[b2 (in-list bl2)])
#:break (not (equal? b1 b2))
1))
(define (bv-common-len bv1 bv1-start bv2 bv2-start)
;; How to avoid this bv copy?? Why is there no drop for sequences either
;; Matthias pls
(for/sum ([b1 (in-bit-vector (bv-copy bv1 bv1-start))]
[b2 (in-bit-vector (bv-copy bv2 bv2-start))])
#:break (not (equal? b1 b2))
1))
(define (rt-partial-iterate node key [start 0])
(define (rt-partial-iterate node key)
(cond
[(>= start (bv-len key)) (list 'exact node)]
[(empty? key) (list 'exact node)]
[else
(let* ([bit (bv-ref key start)]
(let* ([bit (first key)]
[getter (rt-getter bit)]
[next-edge (getter node)]
[next-label (and next-edge (rt-edge-label next-edge))]
[next-target (and next-edge (rt-edge-target next-edge))]
[next-common-len (and next-label (bv-common-len next-label 0 key start))])
[next-common-len (and next-label (bl-common-len next-label key))])
(cond
[(and next-edge (= next-common-len (bv-len next-label)))
(rt-partial-iterate next-target key (+ start next-common-len))]
[next-edge (list 'partial node start next-edge next-common-len)]
[else (list 'no-match node start)]))]))
[(and next-edge (= next-common-len (length next-label)))
(rt-partial-iterate next-target (drop key next-common-len))]
[next-edge (list 'partial node next-edge next-common-len key)]
[else (list 'no-match node key)]))]))
(define (rt-insert! node key data)
(define (insert-node! node key start data)
(let* ([bit (bv-ref key start)]
(define (rt-update! node key updater failure-result)
(define (insert-node! node key)
(let* ([bit (first key)]
[setter! (rt-setter bit)])
(setter! node (rt-edge (bv-copy key start) (rt-node #f #f data)))))
(define (split-node! node key start orig-edge prefix-len data)
(let* ([bit (bv-ref key start)]
(setter! node (rt-edge key (rt-node #f #f (updater (failure-result)))))))
(define (split-node! node key orig-edge prefix-len)
(let* ([bit (first key)]
[setter! (rt-setter bit)]
[orig-label (rt-edge-label orig-edge)]
[orig-target (rt-edge-target orig-edge)]
[new-orig-edge (rt-edge (bv-copy orig-label prefix-len) orig-target)]
[new-insert-edge (rt-edge (bv-copy key (+ start prefix-len)) (rt-node #f #f data))]
[diff-bit (bv-ref key (+ start prefix-len))]
[new-orig-edge (rt-edge (drop orig-label prefix-len) orig-target)]
[new-insert-edge (rt-edge (drop key prefix-len)
(rt-node #f #f (updater (failure-result))))]
[diff-bit (list-ref key prefix-len)]
[common-node (rt-node (if diff-bit new-orig-edge new-insert-edge)
(if diff-bit new-insert-edge new-orig-edge)
#f)]
[common-edge (rt-edge (bv-copy key start (+ start prefix-len)) common-node)])
empty-node-data)]
[common-edge (rt-edge (take key prefix-len) common-node)])
(setter! node common-edge)))
(match (rt-partial-iterate node key)
[(list 'exact node) (set-rt-node-data! data)]
[(list 'partial node start orig-edge prefix-len)
(split-node! node key start orig-edge prefix-len data)]
[(list 'no-match node start)
(insert-node! node key start data)]))
[(list 'exact node)
(set-rt-node-data!
node
(let ([d (rt-node-data node)])
(updater
(if (eq? d empty-node-data) (failure-result) d))))]
[(list 'partial node orig-edge prefix-len partial-key)
(split-node! node partial-key orig-edge prefix-len)]
[(list 'no-match node partial-key)
(insert-node! node partial-key)]))
(define (rt-lookup node key)
(match (rt-partial-iterate node key)
[(list 'exact node) (rt-node-data node)]
[_ #f]))
; (define test (make-rt))
; (define (test-insert! x)
; (rt-insert! test (string->bit-vector x) x))
; (rt-update!
; test
; (map (curry equal? #\1) (string->list x))
; (lambda (_) x)
; (lambda () x)))
; (test-insert! "0001")
; (test-insert! "1000")
; (test-insert! "1010")
; ; (test-insert! "1000")
; ; (test-insert! "1010")
; (test-insert! "0011")
; (test-insert! "0000")
;
; (define (rt-dump node [prefix ""])
; (displayln (format "~a node ~a" prefix (rt-node-data node)))
; (define edge0 (rt-node-edge0 node))
; (define edge1 (rt-node-edge1 node))
; (when edge0
; (displayln (format "~a edge0 ~a" prefix (bit-vector->string (rt-edge-label edge0))))
; (rt-dump (rt-edge-target edge0) (string-append prefix " ")))
; (when edge1
; (displayln (format "~a edge1 ~a" prefix (bit-vector->string (rt-edge-label edge1))))
; (rt-dump (rt-edge-target edge1) (string-append prefix " "))))
; (rt-dump test)
(define (rt-dump node [prefix ""])
(displayln (format "~a node ~a" prefix (rt-node-data node)))
(define edge0 (rt-node-edge0 node))
(define edge1 (rt-node-edge1 node))
(when edge0
(displayln (format "~a edge0 ~a" prefix (rt-edge-label edge0)))
(rt-dump (rt-edge-target edge0) (string-append prefix " ")))
(when edge1
(displayln (format "~a edge1 ~a" prefix (rt-edge-label edge1)))
(rt-dump (rt-edge-target edge1) (string-append prefix " "))))
(rt-dump test)