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#lang debug racket/base
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(require racket/dict racket/sequence "helper.rkt" "number.rkt" "util.rkt" sugar/unstable/dict)
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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 (xarray-decode xa [port-arg (current-input-port)] #:parent [parent #f])
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(define port (->input-port port-arg))
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(define ctx (if (xint? (xarray-len xa))
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(mhasheq 'parent parent
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'_startOffset (pos port)
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'_currentOffset 0
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'_length (xarray-len xa))
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parent))
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(define decoded-len (resolve-length (xarray-len xa) port parent))
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(cond
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[(or (not decoded-len) (eq? (xarray-length-type xa) 'bytes))
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(define end-pos (cond
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;; decoded-len is byte length
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[decoded-len (+ (pos port) decoded-len)]
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;; no decoded-len, but parent has length
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[(and parent (not (zero? (dict-ref parent '_length)))) (+ (dict-ref parent '_startOffset) (dict-ref parent '_length))]
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;; no decoded-len or parent, so consume whole stream
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[else +inf.0]))
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(for/list ([i (in-naturals)]
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#:break (or (eof-object? (peek-byte port)) (= (pos port) end-pos)))
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(decode (xarray-type xa) port #:parent ctx))]
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;; we have decoded-len, which is treated as count of items
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[else (for/list ([i (in-range decoded-len)])
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(decode (xarray-type xa) port #:parent ctx))]))
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(define (xarray-encode xa array [port-arg (current-output-port)] #:parent [parent #f])
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(unless (sequence? array)
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(raise-argument-error 'xarray-encode "sequence" array))
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(define port (if (output-port? port-arg) port-arg (open-output-bytes)))
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(define (encode-items ctx)
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;; todo: should array with fixed length stop encoding after it reaches max?
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;; cf. xstring, which rejects input that is too big for fixed length.
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(let* (#;[items (sequence->list array)]
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#;[item-count (length items)]
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#;[max-items (if (number? (xarray-len xa)) (xarray-len xa) item-count)])
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(for ([item array])
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(encode (xarray-type xa) item port #:parent ctx))))
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(cond
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[(xint? (xarray-len xa))
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(define ctx (mhash 'pointers null
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'startOffset (pos port)
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'parent parent))
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(dict-set! ctx 'pointerOffset (+ (pos port) (size xa array ctx)))
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(encode (xarray-len xa) (length array) port) ; encode length at front
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(encode-items ctx)
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(for ([ptr (in-list (dict-ref ctx 'pointers))]) ; encode pointer data at end
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(encode (dict-ref ptr 'type) (dict-ref ptr 'val) port))]
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[else (encode-items parent)])
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(unless port-arg (get-output-bytes port)))
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(define (xarray-size xa [val #f] [ctx #f])
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(when val (unless (sequence? val)
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(raise-argument-error 'xarray-size "sequence" val)))
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(cond
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[val (let-values ([(ctx len-size) (if (xint? (xarray-len xa))
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(values (mhasheq 'parent ctx) (size (xarray-len xa)))
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(values ctx 0))])
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(+ len-size (for/sum ([item val])
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(size (xarray-type xa) item ctx))))]
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[else (let ([item-count (resolve-length (xarray-len xa) #f ctx)]
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[item-size (size (xarray-type xa) #f ctx)])
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(* item-size item-count))]))
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(struct xarray (type len length-type) #:transparent
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#:methods gen:xenomorphic
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[(define decode xarray-decode)
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(define encode xarray-encode)
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(define size xarray-size)])
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(define (+xarray type [len #f] [length-type 'count])
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(unless (xenomorphic? type)
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(raise-argument-error '+xarray "xenomorphic type" type))
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(unless (length-resolvable? len)
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(raise-argument-error '+xarray "length-resolvable?" len))
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(unless (memq length-type '(bytes count))
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(raise-argument-error '+xarray "'bytes or 'count" length-type))
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(xarray type len length-type))
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(module+ test
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(require rackunit)
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(check-equal? (decode (+xarray uint16be 3) #"ABCDEF") '(16706 17220 17734))
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(check-equal? (encode (+xarray uint16be 3) '(16706 17220 17734) #f) #"ABCDEF")
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(check-equal? (size (+xarray uint16be) '(1 2 3)) 6)
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(check-equal? (size (+xarray doublebe) '(1 2 3 4 5)) 40))
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