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typesetting/pitfall/restructure/struct.rkt

41 lines
1.2 KiB
Racket

#lang restructure/racket
(provide (all-defined-out))
#|
approximates
https://github.com/mbutterick/restructure/blob/master/src/Struct.coffee
|#
(define-subclass RBase (RStruct [fields (mhash)])
(define/override (decode stream [parent #f] [length 0])
(define res (_setup stream parent length))
(_parseFields stream res fields)
(hash-set! (hash-ref res '_props) '_currentOffset (· stream pos))
res)
(define/override (encode stream val [parent #f])
(for ([(key type) (in-hash fields)])
(send type encode stream (hash-ref val key))))
(define/private (_setup stream parent length)
(define res (mhasheq))
;; define hidden properties
(hash-set! res '_props
(mhasheq 'parent (mhasheq 'value parent)
'_startOffset (mhasheq 'value (· stream pos))
'_currentOffset (mhasheq 'value 0 'writable #t)
'_length (mhasheq 'value length)))
res)
(define/private (_parseFields stream res field)
(for ([(key hashvalue) (in-hash fields)])
(define val
(if (procedure? hashvalue)
(hashvalue res)
(send hashvalue decode stream res)))
(hash-set! res key val)))
)