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#lang restructure/racket
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(require "stream.rkt" "sizes.rkt" (for-syntax "sizes.rkt" racket/match))
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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/Number.coffee
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|#
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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 (signed-type? type)
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(not (equal? "u" (substring (symbol->string type) 0 1))))
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(test-module
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(check-false (signed-type? 'uint16))
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(check-true (signed-type? 'int16)))
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(define-subclass Streamcoder (Number [type 'uint16] [endian (if (system-big-endian?) 'be 'le)])
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(getter-field [number-type (string->symbol (format "~a~a" type (if (ends-with-8? type) "" endian)))])
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(define _signed? (signed-type? type))
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;; `get-type-size` will raise error if number-type is invalid: use this as check of input
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;; size of a number doesn't change, so we can stash it as `_size`
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(define _size (with-handlers ([exn:fail:contract?
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(λ (exn)
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(raise-argument-error 'Number "valid type and endian" (format "~v ~v" type endian)))])
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(get-type-size number-type)))
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(define bits (* _size 8))
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(define/override (size . args) _size)
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(define-values (bound-min bound-max)
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;; if a signed integer has n bits, it can contain a number between - (expt 2 (sub1 n)) and (sub1 (expt 2 (sub1 n)).
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(let* ([signed-max (sub1 (arithmetic-shift 1 (sub1 bits)))]
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[signed-min (sub1 (- signed-max))])
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(if _signed?
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(values signed-min signed-max)
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(values (- signed-min signed-min) (- signed-max signed-min)))))
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(define (unsigned->signed uint)
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(define most-significant-bit-mask (arithmetic-shift 1 (sub1 bits)))
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(- (bitwise-xor uint most-significant-bit-mask) most-significant-bit-mask))
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(define (signed->unsigned sint)
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(bitwise-and sint (arithmetic-shift 1 bits)))
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(define/augride (decode stream . args)
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(define bstr (send stream read _size))
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(define system-endian (if (system-big-endian?) 'be 'le))
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(define bs ((if (eq? endian system-endian) identity reverse) (bytes->list bstr)))
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(define unsigned-int (for/sum ([(b i) (in-indexed bs)])
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(arithmetic-shift b (* 8 i))))
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((if _signed? unsigned->signed identity) unsigned-int))
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(define/augride (encode stream val-in)
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(define val ((if (integer? val-in) inexact->exact identity) val-in))
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;; todo: better bounds checking
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(unless (<= bound-min val bound-max)
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(raise-argument-error 'Number:encode (format "value within range of ~a ~a-byte int (~a to ~a)" (if _signed? "signed" "unsigned") _size bound-min bound-max) val))
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(define-values (bs _) (for/fold ([bs empty] [n val])
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([i (in-range _size)])
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(values (cons (bitwise-and n #xff) bs) (arithmetic-shift n -8))))
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(send stream write (apply bytes ((if (eq? endian 'be) identity reverse) bs)))))
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(define-subclass* Number (Fixed size [fixed-endian (if (system-big-endian?) 'be 'le)] [fracBits (floor (/ size 2))])
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(super-make-object (string->symbol (format "int~a" size)) fixed-endian)
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(field [_point (expt 2 fracBits)])
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(define/override (decode stream . args)
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(define result (/ (super decode stream args) _point 1.0))
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(if (integer? result) (inexact->exact result) result))
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(define/override (encode stream val)
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(super encode stream (floor (* val _point)))))
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(define fixed16 (+Fixed 16))
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(define fixed16be (+Fixed 16 'be))
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(define fixed16le (+Fixed 16 'le))
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(define fixed32 (+Fixed 32))
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(define fixed32be (+Fixed 32 'be))
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(define fixed32le (+Fixed 32 'le))
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(test-module
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(check-exn exn:fail:contract? (λ () (+Number 'not-a-valid-type)))
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(check-exn exn:fail:contract? (λ () (send uint8 encode (+EncodeStream) 256)))
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(check-not-exn (λ () (send uint8 encode (+EncodeStream) 255)))
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(check-exn exn:fail:contract? (λ () (send int8 encode (+EncodeStream) 256)))
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(check-exn exn:fail:contract? (λ () (send int8 encode (+EncodeStream) 255)))
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(check-not-exn (λ () (send int8 encode (+EncodeStream) 127)))
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(check-not-exn (λ () (send int8 encode (+EncodeStream) -128)))
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(check-exn exn:fail:contract? (λ () (send int8 encode (+EncodeStream) -129)))
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(check-exn exn:fail:contract? (λ () (send uint16 encode (+EncodeStream) (add1 #xffff))))
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(check-not-exn (λ () (send uint16 encode (+EncodeStream) #xffff)))
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(let ([o (+Number 'uint16 'le)]
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[ip (+DecodeStream (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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(send o encode op 513)
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(check-equal? (get-output-bytes op) (bytes 1 2))
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(send o encode op 1027)
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(check-equal? (get-output-bytes op) (bytes 1 2 3 4)))
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(let ([o (+Number 'uint16 'be)]
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[ip (+DecodeStream (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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(send o encode op 258)
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(check-equal? (get-output-bytes op) (bytes 1 2))
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(send o encode op 772)
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(check-equal? (get-output-bytes op) (bytes 1 2 3 4))))
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(test-module
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(check-equal? (send (+Number 'uint8) size) 1)
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(check-equal? (send (+Number) size) 2)
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(check-equal? (send (+Number 'uint32) size) 4)
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(check-equal? (send (+Number 'double) size) 8))
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;; use keys of type-sizes hash to generate corresponding number definitions
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(define-macro (make-int-types)
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(with-pattern ([((ID BASE ENDIAN) ...) (for/list ([k (in-hash-keys type-sizes)])
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(define kstr (format "~a" k))
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(match-define (list* prefix suffix _)
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(regexp-split #rx"(?=[bl]e|$)" kstr))
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(map string->symbol
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(list (string-downcase kstr)
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prefix
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(if (positive? (string-length suffix))
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suffix
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(if (system-big-endian?) "be" "le")))))]
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[(ID ...) (suffix-id #'(ID ...) #:context caller-stx)]
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[(ID-CLASS ...) (prefix-id "Number:" #'(ID ...))])
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#'(begin (define+provide ID (let ([ID-CLASS (class Number (super-new))])
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(make-object ID-CLASS 'BASE 'ENDIAN))) ...)))
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(make-int-types)
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(test-module
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(check-equal? (send uint8 size) 1)
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(check-equal? (send uint16 size) 2)
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(check-equal? (send uint32 size) 4)
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(check-equal? (send double size) 8)
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(define es (+EncodeStream))
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(send fixed16be encode es 123.45)
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(check-equal? (send es dump) #"{s")
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(define ds (+DecodeStream (send es dump)))
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#;(check-equal? (ceiling (* (send fixed16be decode ds) 100)) 12345.0)
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(check-equal? (send int8 decode (bytes 127)) 127)
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(check-equal? (send int8 decode (bytes 255)) -1)
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(check-equal? (send int8 encode #f -1) (bytes 255))
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(check-equal? (send int8 encode #f 127) (bytes 127))
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)
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