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#lang restructure/racket
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(require "number.rkt" "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 (Array type [_length #f] [lengthType 'count])
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(define/augride (decode stream [parent #f])
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(let ([len (cond
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;; explicit length
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[_length (resolveLength _length stream parent)]
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[else ;; implicit length: length of stream divided by size of item
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(define num (send stream length))
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(define denom (send type size))
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(unless (andmap (λ (x) (and x (number? x))) (list num denom))
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(raise-argument-error 'Array:decode "valid length and size" (list num denom)))
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(floor (/ (send stream length) (send type size)))])])
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(caseq lengthType
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[(count) (for/list ([i (in-range len)])
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(send type decode stream this))])))
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(define/override (size array)
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(unless (list? array) (raise-argument-error 'Array:size "list" array))
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(* (send type size) (length array)))
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(define/augride (encode stream array [parent #f])
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(unless (list? array) (raise-argument-error 'Array:encode "list" array))
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(for ([item (in-list array)])
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(send type encode stream item))))
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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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(define os (+EncodeStream))
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(send A encode os '(16706 17220 17734))
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(check-equal? (send os dump) #"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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#|
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approximates
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https://github.com/mbutterick/restructure/blob/master/src/LazyArray.coffee
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|#
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(define-subclass object% (InnerLazyArray type [_length #f] [stream #f] [ctx #f])
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(field [base (· stream pos)]
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[items (mhash)]) ; implement with hash (random add) rather than array
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(define/public-final (get index)
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(when (or (< index 0) (<= _length index))
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(raise-argument-error 'InnerLazyArray:get (format "non-negative index less than length ~a of array" _length) index))
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(hash-ref! items index (λ ()
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(define stashed-pos (· stream pos))
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(send stream pos (+ base (* index (send type size))))
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(define new-val (send type decode stream ctx))
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(send stream pos stashed-pos)
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new-val)))
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(define/public-final (toArray)
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(for/list ([i (in-range _length)])
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(get i))))
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(define-subclass Array (LazyArray)
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(inherit-field _length type)
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(define/override (decode stream [parent #f])
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(define len (resolveLength _length stream parent))
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(define res (+InnerLazyArray type len stream parent))
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(send stream pos (+ (· stream pos) (* _length (send type size)))) ; skip the bytes that LazyArray would occupy
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res)
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(define/override (size val)
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(super size (if (InnerLazyArray? val)
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(send val toArray)
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val)))
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(define/override (encode stream val)
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(super encode (if (InnerLazyArray? val)
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(send val toArray)
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val))))
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(test-module
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(define bstr #"ABCD1234")
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(define ds (+DecodeStream bstr))
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(define la (+LazyArray uint8 4))
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(define ila (send la decode ds))
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(check-equal? (send ds pos) 4)
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(check-equal? (send ila get 1) 66)
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(check-equal? (send ila get 3) 68)
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(check-equal? (send ds pos) 4)
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(check-equal? (send ila toArray) '(65 66 67 68)))
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