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#lang restructure/racket
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(require "decodestream.rkt")
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;; approximates https://github.com/mbutterick/restructure/blob/master/src/Number.coffee
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(define (ends-with-8? type)
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(define str (symbol->string type))
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(equal? (substring str (sub1 (string-length str))) "8"))
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(define (unsigned-type? type)
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(equal? "U" (substring (symbol->string type) 0 1)))
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(test-module
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(check-true (unsigned-type? 'UInt16))
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(check-false (unsigned-type? 'Int16)))
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(define-subclass RestructureBase% (NumberT type [endian (if (system-big-endian?) 'BE 'LE)])
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(getter-field [fn (string->symbol (format "~a~a" type (if (ends-with-8? type) "" endian)))])
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(unless (hash-has-key? type-sizes fn)
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(raise-argument-error 'NumberT "valid type and endian" (format "~v ~v" type endian)))
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(getter-field [size (hash-ref type-sizes fn)])
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(define/override (decode stream)
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(unless (input-port? stream)
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(raise-argument-error 'decode "input port" stream))
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(define bstr (read-bytes-exact size stream))
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(if (= 1 size)
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(bytes-ref bstr 0)
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(integer-bytes->integer bstr (unsigned-type? type) (eq? endian 'BE))))
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(define/override (encode stream val)
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(unless (output-port? stream)
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(raise-argument-error 'encode "output port" stream))
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(if (= 1 size)
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(bytes val)
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(integer->integer-bytes val size (unsigned-type? type) (eq? endian 'BE)))))
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(test-module
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(let ([o (make-object NumberT 'UInt16 'LE)]
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[ip (open-input-bytes (bytes 1 2 3 4))]
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[op (open-output-bytes)])
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(check-equal? (send o decode ip) 513) ;; 1000 0000 0100 0000
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(check-equal? (send o decode ip) 1027) ;; 1100 0000 0010 0000
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(check-equal? (send o encode op 513) (bytes 1 2))
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(check-equal? (send o encode op 1027) (bytes 3 4)))
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(let ([o (make-object NumberT 'UInt16 'BE)]
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[ip (open-input-bytes (bytes 1 2 3 4))]
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[op (open-output-bytes)])
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(check-equal? (send o decode ip) 258) ;; 0100 0000 1000 0000
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(check-equal? (send o decode ip) 772) ;; 0010 0000 1100 0000
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(check-equal? (send o encode op 258) (bytes 1 2))
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(check-equal? (send o encode op 772) (bytes 3 4))))
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(test-module
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(check-equal? (send (make-object NumberT 'UInt8) size) 1)
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(check-equal? (send (make-object NumberT 'UInt32) size) 4)
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(check-equal? (send (make-object NumberT 'Double) size) 8))
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