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#lang reader (submod "racket.rkt" reader)
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(require racket/dict "stream.rkt" racket/private/generic-methods racket/struct)
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(provide (all-defined-out) ref* ref*-set! (all-from-out racket/dict))
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(require (prefix-in d: racket/dict))
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#|
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approximates
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https://github.com/mbutterick/restructure/blob/master/src/Struct.coffee
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|#
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(define private-keys '(parent _startOffset _currentOffset _length))
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(define (choose-dict d k)
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(if (memq k private-keys)
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(get-field _pvt d)
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(get-field _kv d)))
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(define dictable<%>
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(interface* ()
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([(generic-property gen:dict)
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(generic-method-table gen:dict
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(define (dict-set! d k v) (d:dict-set! (choose-dict d k) k v))
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(define (dict-ref d k [thunk #f])
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(define res (d:dict-ref (choose-dict d k) k thunk))
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(if (LazyThunk? res) ((LazyThunk-proc res)) res))
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(define (dict-remove! d k) (d:dict-remove! (choose-dict d k) k))
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;; public keys only
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(define (dict-keys d) (d:dict-keys (get-field _kv d))))]
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[(generic-property gen:custom-write)
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(generic-method-table gen:custom-write
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(define (write-proc o port mode)
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(define proc (case mode
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[(#t) write]
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[(#f) display]
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[else (λ (p port) (print p port mode))]))
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(proc (get-field _kv o) port)))])))
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(define StructDictRes (class* RestructureBase (dictable<%>)
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(super-make-object)
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(field [_kv (mhasheq)]
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[_pvt (mhasheq)])
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(define/override (dump) _kv)))
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(define-subclass Streamcoder (Struct [fields (dictify)])
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(field [[_process process] (λ (res stream ctx) res)]
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[[_preEncode preEncode] void]) ; store as field so it can be mutated from outside
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(define/overment (process res stream [ctx #f])
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(let* ([res (_process res stream ctx)]
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[res (inner res process res stream ctx)])
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(unless (dict? res) (raise-result-error 'Struct:process "dict" res))
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res))
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(define/override (preEncode . args) (apply _preEncode args))
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(unless ((disjoin assocs? Struct?) fields) ; should be Versioned Struct but whatever
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(raise-argument-error 'Struct "assocs or Versioned Struct" fields))
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(define/augride (decode stream [parent #f] [len 0])
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;; _setup and _parse-fields are separate to cooperate with VersionedStruct
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(let* ([res (_setup stream parent len)]
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[res (_parse-fields stream res fields)]
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[res (process res stream)])
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res))
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(define/public-final (_setup stream parent len)
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(define res (make-object StructDictRes)) ; not mere hash
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(dict-set*! res 'parent parent
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'_startOffset (· stream pos)
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'_currentOffset 0
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'_length len)
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res)
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(define/public-final (_parse-fields stream res fields)
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(unless (assocs? fields)
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(raise-argument-error '_parse-fields "assocs" fields))
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(for/fold ([res res])
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([(key type) (in-dict fields)])
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(define val (if (procedure? type)
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(type res)
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(send type decode stream res)))
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(unless (void? val)
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(ref-set! res key val))
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(ref-set! res '_currentOffset (- (· stream pos) (· res _startOffset)))
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res))
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(define/override (size [val #f] [parent #f] [include-pointers #t])
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(define ctx (mhasheq 'parent parent
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'val val
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'pointerSize 0))
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(+ (for/sum ([(key type) (in-dict fields)])
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(send type size (and val (ref val key)) ctx))
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(if include-pointers (· ctx pointerSize) 0)))
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(define/augride (encode stream val [parent #f])
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(unless (dict? val)
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(raise-argument-error 'Struct:encode "dict" val))
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(send this preEncode val stream) ; preEncode goes first, because it might bring input dict into compliance
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(define ctx (mhash 'pointers empty
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'startOffset (· stream pos)
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'parent parent
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'val val
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'pointerSize 0))
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(ref-set! ctx 'pointerOffset (+ (· stream pos) (size val ctx #f)))
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(unless (andmap (λ (key) (memq key (dict-keys val))) (dict-keys fields))
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(raise-argument-error 'Struct:encode
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(format "dict that contains superset of Struct keys: ~a" (dict-keys fields)) (dict-keys val)))
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(for ([(key type) (in-dict fields)])
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(send type encode stream (ref val key) ctx))
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(for ([ptr (in-list (· ctx pointers))])
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(send (· ptr type) encode stream (· ptr val) (· ptr parent)))))
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(test-module
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(require "number.rkt")
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(define (random-pick xs) (list-ref xs (random (length xs))))
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(check-exn exn:fail:contract? (λ () (+Struct 42)))
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;; make random structs and make sure we can round trip
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(for ([i (in-range 20)])
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(define field-types (for/list ([i (in-range 40)])
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(random-pick (list uint8 uint16be uint16le uint32be uint32le double))))
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(define size-num-types (for/sum ([num-type (in-list field-types)])
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(send num-type size)))
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(define s (+Struct (for/list ([num-type (in-list field-types)])
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(cons (gensym) num-type))))
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(define bs (apply bytes (for/list ([i (in-range size-num-types)])
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(random 256))))
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(check-equal? (send s encode #f (send s decode bs)) bs)))
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