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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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(inherit-field res)
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(define/augride (decode stream [parent #f])
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(when parent
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(unless (hash? parent)
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(raise-argument-error 'Array:decode "hash" parent)))
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(define pos (send stream pos))
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(define res empty)
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(define ctx parent)
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(define length__
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(or length_ (resolveLength length_ stream parent)))
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(when (NumberT? length_)
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;; define hidden properties
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(hash-set*! (hash-ref ctx '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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#;(define length__ (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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#;(define res (caseq lengthType
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[(bytes) (error 'array-decode-bytes-no!)]
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[(count) (for/list ([i (in-range length__)])
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(send type decode stream ctx))]))
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res)
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(define/override (size [array #f])
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(when (and array (not (list? array)))
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(raise-argument-error 'Array:size "list" array))
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(cond
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[(not array) (* (send type size) (resolveLength length_ (+DecodeStream) #f))]
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[(Number? length_) (send length_ size)]
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[else (* (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] [parent #f])
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(field [base (and stream (· 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 "array index between 0 and ~a" _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 parent))
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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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(define lazy-space (* len (send type size)))
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(report lazy-space)
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(send stream pos (+ (· stream pos) lazy-space)) ; skip the bytes that LazyArray would occupy
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res)
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(define/override (size [val #f])
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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 stream (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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(define la2 (+LazyArray int16be (λ (t) 4)))
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(define es (+EncodeStream))
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(send la2 encode es '(1 2 3 4))
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(check-equal? (send es dump) #"\0\1\0\2\0\3\0\4")
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(check-equal? (send (send la2 decode (+DecodeStream #"\0\1\0\2\0\3\0\4")) toArray) '(1 2 3 4))
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)
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