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#lang reader (submod "racket.rkt" reader)
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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/String.coffee
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|#
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(define (byte-length val encoding)
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(define encoder
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(caseq encoding
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[(ascii utf8) string->bytes/utf-8]))
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(bytes-length (encoder (format "~a" val))))
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(define-subclass Streamcoder (StringT [len #f] [encoding 'ascii])
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(define/augment (decode stream [parent #f])
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(let ([len (or (resolve-length len stream parent) (send stream count-nonzero-chars))]
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[encoding (if (procedure? encoding)
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(or (encoding parent) 'ascii)
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encoding)]
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[adjustment (if (and (not len) (< (· stream pos) (· stream length))) 1 0)])
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(define string (send stream readString len encoding))
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(send stream pos (+ (· stream pos) adjustment))
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string))
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(define/augment (encode stream val [parent #f])
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(let* ([val (format "~a" val)]
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[encoding (if (procedure? encoding)
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(or (encoding (and parent (· parent val)) 'ascii))
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encoding)])
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(when (NumberT? len)
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(send len encode stream (byte-length val encoding)))
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(send stream writeString val encoding)
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(when (not len) (send stream writeUInt8 #x00)))) ; null terminated when no len
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(define/augment (size [val #f] [parent #f])
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(if (not val)
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(resolve-length len #f parent)
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(let* ([encoding (if (procedure? encoding)
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(or (encoding (and parent (· parent val)) 'ascii))
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encoding)]
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[encoding (if (eq? encoding 'utf16be) 'utf16le encoding)])
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(+ (byte-length val encoding) (cond
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[(not len) 1]
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[(NumberT? len) (send len size)]
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[else 0]))))))
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(define-values (String? +String) (values StringT? +StringT))
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(test-module
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(require "stream.rkt")
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(define S (+String uint8 'utf8))
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(check-equal? (send S decode #"\2BCDEF") "BC")
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(check-equal? (send S encode #f "Mike") #"\4Mike")
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(check-equal? (send (+String) size "foobar") 7)) ; null terminated when no len
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