You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
typesetting/pitfall/restructure/array.rkt

47 lines
1.7 KiB
Racket

#lang restructure/racket
(require "number.rkt" "utils.rkt" "stream.rkt")
(provide (all-defined-out))
#|
approximates
https://github.com/mbutterick/restructure/blob/master/src/Array.coffee
|#
(define-subclass Streamcoder (Array type [_length #f] [lengthType 'count])
(define/augment (decode stream [parent #f])
(let ([len (cond
;; explicit length
[_length (resolveLength _length stream parent)]
[else ;; implicit length: length of stream divided by size of item
(define num (send stream length))
(define denom (send type size))
(unless (andmap (λ (x) (and x (number? x))) (list num denom))
(raise-argument-error 'Array:decode "valid length and size" (list num denom)))
(floor (/ (send stream length) (send type size)))])])
(caseq lengthType
[(count) (for/list ([i (in-range len)])
(send type decode stream this))])))
(define/override (size array)
(unless (list? array) (raise-argument-error 'Array:size "list" array))
(* (send type size) (length array)))
(define/augment (encode stream array [parent #f])
(unless (list? array) (raise-argument-error 'Array:encode "list" array))
(for ([item (in-list array)])
(send type encode stream item))))
(test-module
(define stream (+DecodeStream #"ABCDEFG"))
(define A (+Array uint16be 3))
(check-equal? (send A decode stream) '(16706 17220 17734))
(define os (+EncodeStream))
(send A encode os '(16706 17220 17734))
(check-equal? (send os dump) #"ABCDEF")
(check-equal? (send (+Array uint16be) size '(1 2 3)) 6)
(check-equal? (send (+Array doublebe) size '(1 2 3 4 5)) 40))