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#lang restructure/racket
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(require "number.rkt" (prefix-in utils- "utils.rkt") "stream.rkt")
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(provide (all-defined-out))
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#|
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approximates
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https://github.com/mbutterick/restructure/blob/master/src/Array.coffee
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|#
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(define-subclass Streamcoder (ArrayT type [length_ #f] [lengthType 'count])
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(define/augride (decode stream [parent #f])
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(define pos (send stream pos))
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(define res (make-object RestructureBase)) ; instead of empty list
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(define ctx parent)
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(define length__
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(and length_ (utils-resolveLength length_ stream parent)))
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(when (NumberT? length_)
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;; define hidden properties
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(ref-set*! res 'parent parent
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'_startOffset pos
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'_currentOffset 0
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'_length length_)
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(set! ctx res))
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(cond
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[(or (not length__) (eq? lengthType 'bytes))
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(define target (cond
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[length__ (+ (send stream pos) length__)]
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[(and parent (· parent _length))
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(+ (ref parent '_startOffset)
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(ref parent '_length))]
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[else (· stream length_)]))
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(ref-set! res '_list
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(push-end res
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(for/list ([i (in-naturals)]
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#:break (= (send stream pos) target))
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(send type decode stream ctx))))]
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[else
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(ref-set! res '_list
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(push-end res
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(for/list ([i (in-range length__)])
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(send type decode stream ctx))))])
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(countable->list res))
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(define/override (size [array #f] [ctx #f])
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(when array
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(unless (countable? array)
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(raise-argument-error 'Array:size "list or countable" array)))
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(cond
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[(not array)
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(* (send type size #f ctx) (utils-resolveLength length_ #f ctx))]
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[else
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(+ (cond
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[(NumberT? length_)
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(set! ctx (mhash 'parent ctx))
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(send length_ size)]
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[else 0])
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(for/sum ([item (in-list (countable->list array))])
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(send type size item ctx)))]))
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(define/augride (encode stream array [parent #f])
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(when array (unless (countable? array)
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(raise-argument-error 'Array:encode "list or countable" array)))
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(define ctx parent)
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(when (NumberT? length_)
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(set! ctx (mhash 'pointers null
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'startOffset (· stream pos)
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'parent parent))
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(ref-set! ctx 'pointerOffset (+ (· stream pos) (size array ctx)))
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(send length_ encode stream (length array)))
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(for ([item (in-list (countable->list array))])
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(send type encode stream item ctx))
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(when (NumberT? length_)
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(for ([ptr (in-list (· ctx pointers))])
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(send (· ptr type) encode stream (· ptr val))))))
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(define-values (Array Array? +Array) (values ArrayT ArrayT? +ArrayT))
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(test-module
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(define stream (+DecodeStream #"ABCDEFG"))
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(define A (+Array uint16be 3))
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(check-equal? (send A decode stream) '(16706 17220 17734))
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(check-equal? (send A encode #f '(16706 17220 17734)) #"ABCDEF")
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(check-equal? (send (+Array uint16be) size '(1 2 3)) 6)
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(check-equal? (send (+Array doublebe) size '(1 2 3 4 5)) 40))
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