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typesetting/pitfall/restructure/array.rkt

43 lines
1.5 KiB
Racket

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#lang restructure/racket
(require "number.rkt" "utils.rkt" "streamcoder.rkt")
(provide RArray)
#|
approximates
https://github.com/mbutterick/restructure/blob/master/src/Array.coffee
|#
(define-subclass RStreamcoder (RArray type [length #f] [lengthType 'count])
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(define/augment (decode stream [parent #f])
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(let ([length (cond
[length
(resolveLength length stream parent)]
[else
(define num (send stream length))
(define denom (send type size))
(unless (andmap (λ (x) (and x (number? x))) (list num denom))
(raise-argument-error 'RArray:decode "valid length and size" (list num denom)))
;; implied length: length of stream divided by size of item
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(floor (/ (send stream length) (send type size)))])])
(caseq lengthType
[(count) (for/list ([i (in-range length)])
(send type decode stream this))])))
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(define/public (size) (unfinished))
(define/augment (encode stream array [parent #f])
(for ([item (in-list array)])
(send type encode stream item))))
(test-module
(require "decodestream.rkt" "encodestream.rkt")
(define stream (make-object RDecodeStream #"ABCDEFG"))
(define A (make-object RArray uint16be 3))
(check-equal? (send A decode stream) '(16706 17220 17734))
(define os (make-object REncodeStream))
(send A encode os '(16706 17220 17734))
(check-equal? (send os dump) #"ABCDEF"))