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60 lines
2.3 KiB
Racket
60 lines
2.3 KiB
Racket
#lang restructure/racket
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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/Pointer.coffee
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|#
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(define-subclass object% (Pointer offsetType type [scope 'local])
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(when (eq? type 'void) (set! type #f))
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(and (symbol? scope) (caseq scope
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[(local parent immediate global) 'yay]
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[else (raise-argument-error 'Pointer "local or parent or immediate" scope)]))
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(define/public (decode stream [ctx #f])
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(define offset (send offsetType decode stream ctx))
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(report scope 'pointer-scope)
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(define relative (caseq scope
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[(local) (when (and (· ctx res _startOffset) (· ctx _startOffset)
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(not (= (· ctx res _startOffset) (· ctx _startOffset))))
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(report* ctx (· ctx res _startOffset) (· ctx _startOffset))
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(error 'bazongas))
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(· ctx _startOffset)]
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[(parent) (· ctx parent _startOffset)]
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[(immediate) (- (· stream pos) (send offsetType size))]
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[(global)
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(let loop ([c ctx])
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(cond
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[(· c parent) => loop]
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[(· c _startOffset)]
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[else 0]))]))
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(report* this (· this _startOffset)
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(and (· this res) (· this res _startOffset))
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ctx (and ctx (· ctx _startOffset))
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(and (· ctx res) (· ctx res _startOffset)))
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(when (and ctx (· ctx _startOffset) (= (· ctx _startOffset) 1012)) (error 'stop))
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(report* offset relative)
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(define ptr (+ offset relative))
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(report* ptr)
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(report (send offsetType size) 'size)
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(cond
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[type (define orig-pos (send stream pos))
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(send stream pos ptr)
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(define val (send type decode stream ctx))
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(send stream pos orig-pos)
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val]
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[else ptr]))
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(define/public (encode stream val)
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(error 'Pointer-encode-not-done))
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(define/public (size [val #f] [ctx #f])
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(error 'Pointer-size-not-done)
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(report* this offsetType type (send type size)))
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) |