You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
90 lines
3.9 KiB
Racket
90 lines
3.9 KiB
Racket
#lang restructure/racket
|
|
(provide (all-defined-out))
|
|
|
|
#|
|
|
approximates
|
|
https://github.com/mbutterick/restructure/blob/master/src/Pointer.coffee
|
|
|#
|
|
|
|
(define (resolve-void-pointer type val)
|
|
(cond
|
|
[type (values type val)]
|
|
[(VoidPointer? val) (values (· val type) (· val value))]
|
|
[else (raise-argument-error 'Pointer:size "VoidPointer" val)]))
|
|
|
|
(define (find-top-ctx ctx)
|
|
(cond
|
|
[(· ctx parent) => find-top-ctx]
|
|
[else ctx]))
|
|
|
|
(define-subclass object% (Pointer offset-type type-in [options (mhasheq)])
|
|
(field [type (and (not (eq? type-in 'void)) type-in)])
|
|
(define pointer-style (or (· options type) 'local))
|
|
(define allow-null (or (· options allowNull) #t))
|
|
(define null-value (or (· options nullValue) 0))
|
|
(define lazy (· options lazy))
|
|
(define relative-getter-or-0 (or (· options relativeTo) (λ (ctx) 0))) ; changed this to a simple lambda
|
|
|
|
(define/public (decode stream [ctx #f])
|
|
(define offset (send offset-type decode stream ctx))
|
|
(cond
|
|
[(and allow-null (= offset null-value)) #f] ; handle null pointers
|
|
[else
|
|
(define relative (+ (caseq pointer-style
|
|
[(local) (· ctx _startOffset)]
|
|
[(immediate) (- (· stream pos) (send offset-type size))]
|
|
[(parent) (· ctx parent _startOffset)]
|
|
[(global) (or (· (find-top-ctx ctx) _startOffset) 0)]
|
|
[else (error 'unknown-pointer-style)])
|
|
(relative-getter-or-0 ctx)))
|
|
(define ptr (+ offset relative))
|
|
(cond ; omitted: lazy pointer implementation
|
|
[type (define orig-pos (· stream pos))
|
|
(send stream pos ptr)
|
|
(define val (send type decode stream ctx))
|
|
(send stream pos orig-pos)
|
|
val]
|
|
[else ptr])]))
|
|
|
|
|
|
(define/public (size [val #f] [ctx #f])
|
|
(let*-values ([(parent) ctx]
|
|
[(ctx) (caseq pointer-style
|
|
[(local immediate) ctx]
|
|
[(parent) (· ctx parent)]
|
|
[(global) (find-top-ctx ctx)]
|
|
[else (error 'unknown-pointer-style)])]
|
|
[(type val) (resolve-void-pointer type val)])
|
|
(when (and val ctx)
|
|
(ref-set! ctx 'pointerSize (and (· ctx pointerSize)
|
|
(+ (· ctx pointerSize) (send type size val parent)))))
|
|
(send offset-type size)))
|
|
|
|
|
|
(define/public (encode stream val [ctx #f])
|
|
(if (not val)
|
|
(send offset-type encode stream null-value)
|
|
(let* ([parent ctx]
|
|
[ctx (caseq pointer-style
|
|
[(local immediate) ctx]
|
|
[(parent) (· ctx parent)]
|
|
[(global) (find-top-ctx ctx)]
|
|
[else (error 'unknown-pointer-style)])]
|
|
[relative (+ (caseq pointer-style
|
|
[(local parent) (· ctx startOffset)]
|
|
[(immediate) (+ (· stream pos) (send offset-type size val parent))]
|
|
[(global) 0])
|
|
(relative-getter-or-0 (· parent val)))])
|
|
|
|
(send offset-type encode stream (- (· ctx pointerOffset) relative))
|
|
|
|
(let-values ([(type val) (resolve-void-pointer type val)])
|
|
(ref-set! ctx 'pointers (append (· ctx pointers) (list (mhasheq 'type type
|
|
'val val
|
|
'parent parent))))
|
|
(ref-set! ctx 'pointerOffset (+ (· ctx pointerOffset) (send type size val parent))))))))
|
|
|
|
|
|
;; A pointer whose type is determined at decode time
|
|
(define-subclass object% (VoidPointer type value))
|