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118 lines
5.0 KiB
Racket
118 lines
5.0 KiB
Racket
#lang restructure/racket
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(require racket/dict "struct.rkt")
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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/VersionedStruct.coffee
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|#
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(define-subclass Struct (VersionedStruct type [versions (dictify)])
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(inherit-field res)
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(unless ((disjoin integer? procedure? RestructureBase? symbol?) type)
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(raise-argument-error 'VersionedStruct "integer, function, symbol, or Restructure object" type))
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(unless (and (dict? versions) (andmap (λ (val) (or (dict? val) (Struct? val))) (map cdr versions)))
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(raise-argument-error 'VersionedStruct "dict of dicts or Structs" versions))
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(inherit-field fields)
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(field [forced-version #f])
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(define/public-final (force-version! version)
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(set! forced-version version))
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(define/public (resolve-version [stream #f] [parent #f])
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(cond
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[forced-version] ; for testing purposes: pass an explicit version
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[(integer? type) type]
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[(symbol? type)
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;; find the first Struct in the chain of ancestors
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;; with the target key
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(let loop ([x parent])
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(cond
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[(and x (Struct? x) (dict-ref (· x res) type #f))]
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[(· x parent) => loop]
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[else #f]))]
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[(and (procedure? type) (positive? (procedure-arity type))) (type parent)]
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[(RestructureBase? type) (send type decode stream)]
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[else (raise-argument-error 'VersionedStruct:resolve-version "way of finding version" type)]))
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(define/override (decode stream [parent #f] [length 0])
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(set! res (send this _setup stream parent length))
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(report res 'versioned-struct-res)
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(define version (resolve-version stream parent))
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(hash-set! res 'version version)
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(define fields (dict-ref versions version (λ () (raise-argument-error 'VersionedStruct:decode "valid version key" (cons version (· this versions))))))
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(cond
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[(VersionedStruct? fields) (send fields decode stream parent)]
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[else
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(report res 'whatigot)
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(send this _parseFields stream res fields)
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(send this process res stream)
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res]))
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(define/override (encode stream input-hash [parent #f])
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(unless (hash? input-hash)
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(raise-argument-error 'Struct:encode "hash" input-hash))
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(send this preEncode input-hash stream) ; preEncode goes first, because it might bring input hash into compliance
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(define fields (dict-ref versions (· input-hash version) (λ () (raise-argument-error 'VersionedStruct:encode "valid version key" version))))
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(unless (andmap (λ (key) (member key (hash-keys input-hash))) (dict-keys fields))
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(raise-argument-error 'Struct:encode (format "hash that contains superset of Struct keys: ~a" (dict-keys fields)) (hash-keys input-hash)))
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(cond
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[(dict? fields)
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(for* ([(key type) (in-dict fields)])
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(send type encode stream (hash-ref input-hash key)))]
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[else (send fields encode stream input-hash parent)]))
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(define/override (size [input-hash (mhash)] [parent #f] [includePointers #t])
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(when (and (not input-hash) (not forced-version))
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(error 'VersionedStruct-cannot-compute-size))
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(define version (resolve-version #f parent))
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(define fields (dict-ref versions version (λ () (raise-argument-error 'VersionedStruct:size "valid version key" version))))
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(cond
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[(dict? fields)
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(for/sum ([(key type) (in-dict fields)])
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(define val (hash-ref input-hash key #f))
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(define args (if val (list val) empty))
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(send type size . args))]
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[else (send fields size input-hash parent includePointers)])))
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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 () (+VersionedStruct 42 42)))
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;; make random versioned 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 200)])
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(random-pick (list uint8 uint16be uint16le uint32be uint32le double))))
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(define num-versions 20)
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(define which-struct (random num-versions))
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(define struct-versions (for/list ([v (in-range num-versions)])
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(cons v (for/list ([num-type (in-list field-types)])
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(cons (gensym) num-type)))))
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(define vs (+VersionedStruct which-struct struct-versions))
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(define struct-size (for/sum ([num-type (in-list (map cdr (dict-ref struct-versions which-struct)))])
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(send num-type size)))
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(define bs (apply bytes (for/list ([i (in-range struct-size)])
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(random 256))))
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(check-equal? (send vs encode #f (send vs decode bs)) bs))
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(define s (+Struct (dictify 'a uint8 'b uint8 'c uint8)))
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(check-equal? (send s size) 3)
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(define vs (+VersionedStruct (λ (p) 2) (dictify 1 (dictify 'd s) 2 (dictify 'e s 'f s))))
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(check-equal? (send vs size) 6)
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(define s2 (+Struct (dictify 'a vs)))
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(check-equal? (send s2 size) 6)
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(define vs2 (+VersionedStruct (λ (p) 2) (dictify 1 vs 2 vs)))
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(check-equal? (send vs2 size) 6)
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)
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