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typesetting/pitfall/restructure/versioned-struct.rkt

156 lines
6.2 KiB
Racket

#lang restructure/racket
(require racket/dict "struct.rkt")
(provide (all-defined-out))
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#|
approximates
https://github.com/mbutterick/restructure/blob/master/src/VersionedStruct.coffee
|#
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(define-subclass Struct (VersionedStruct type [versions (dictify)])
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(unless ((disjoin integer? procedure? RestructureBase? symbol?) type)
(raise-argument-error 'VersionedStruct "integer, function, symbol, or Restructure object" type))
(unless (and (dict? versions) (andmap (λ (val) (or (dict? val) (Struct? val))) (map cdr versions)))
(raise-argument-error 'VersionedStruct "dict of dicts or Structs" versions))
(inherit _setup _parseFields process)
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(inherit-field fields)
(field [forced-version #f]
[versionGetter void]
[versionSetter void])
(when (or (key? type) (procedure? type))
(set-field! versionGetter this (if (procedure? type)
type
(λ (parent) (ref parent type))))
(set-field! versionSetter this (if (procedure? type)
type
(λ (parent version) (ref-set! parent type version)))))
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(define/override (decode stream [parent #f] [length 0])
(define res (_setup stream parent length))
(ref-set! res 'version
(cond
[forced-version] ; for testing purposes: pass an explicit version
[(or (key? type) (procedure? type))
(unless parent
(raise-argument-error 'VersionedStruct:decode "valid parent" parent))
(versionGetter parent)]
[else (send type decode stream)]))
(when (ref versions 'header)
(_parseFields stream res (ref versions 'header)))
(define fields (or (ref versions (ref res 'version)) (raise-argument-error 'VersionedStruct:decode "valid version key" (cons version (· this versions)))))
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(cond
[(VersionedStruct? fields) (send fields decode stream parent)]
[else
(_parseFields stream res fields)
(process res stream)
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res]))
(define/public-final (force-version! version)
(set! forced-version version))
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(define/override (encode stream val [parent #f])
(unless (hash? val)
(raise-argument-error 'Struct:encode "hash" val))
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(send this preEncode val stream) ; preEncode goes first, because it might bring input hash into compliance
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(define ctx (mhash 'pointers empty
'startOffset (· stream pos)
'parent parent
'val val
'pointerSize 0))
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(ref-set! ctx 'pointerOffset (+ (· stream pos) (size val ctx #f)))
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(when (not (or (key? type) (procedure? type)))
(send type encode stream (or forced-version (· val version))))
(when (ref versions 'header)
(for ([(key type) (in-dict (ref versions 'header))])
(send type encode stream (ref val key) ctx)))
(define fields (or (ref versions (or forced-version (· val version))) (raise-argument-error 'VersionedStruct:encode "valid version key" version)))
(unless (andmap (λ (key) (member key (ref-keys val))) (ref-keys fields))
(raise-argument-error 'VersionedStruct:encode (format "hash that contains superset of Struct keys: ~a" (dict-keys fields)) (hash-keys val)))
(for ([(key type) (in-dict fields)])
(send type encode stream (ref val key) ctx))
(for ([ptr (in-list (ref ctx 'pointers))])
(send (ref ptr 'type) encode stream (ref ptr 'val) (ref ptr 'parent))))
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(define/override (size [val (mhash)] [parent #f] [includePointers #t])
(unless (or val forced-version)
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(error 'VersionedStruct-cannot-compute-size))
(define ctx (mhash 'parent parent
'val val
'pointerSize 0))
(define size 0)
(when (not (or (key? type) (procedure? type)))
(increment! size (send type size (or forced-version (ref val 'version)) ctx)))
(when (ref versions 'header)
(increment! size
(for/sum ([(key type) (in-dict (ref versions 'header))])
(send type size (ref val key) ctx))))
(define fields (or (ref versions (or forced-version (ref val 'version))) (raise-argument-error 'VersionedStruct:encode "valid version key" version)))
(increment! size
(for/sum ([(key type) (in-dict fields)])
(send type size (ref val key) ctx)))
(when includePointers
(increment! size (ref ctx 'pointerSize)))
size))
#;(test-module
(require "number.rkt")
(define (random-pick xs) (list-ref xs (random (length xs))))
(check-exn exn:fail:contract? (λ () (+VersionedStruct 42 42)))
;; make random versioned structs and make sure we can round trip
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#;(for ([i (in-range 1)])
(define field-types (for/list ([i (in-range 1)])
(random-pick (list uint8 uint16be uint16le uint32be uint32le double))))
(define num-versions 20)
(define which-struct (random num-versions))
(define struct-versions (for/list ([v (in-range num-versions)])
(cons v (for/list ([num-type (in-list field-types)])
(cons (gensym) num-type)))))
(define vs (+VersionedStruct which-struct struct-versions))
(define struct-size (for/sum ([num-type (in-list (map cdr (ref struct-versions which-struct)))])
(send num-type size)))
(define bs (apply bytes (for/list ([i (in-range struct-size)])
(random 256))))
(check-equal? (send vs encode #f (send vs decode bs)) bs))
(define s (+Struct (dictify 'a uint8 'b uint8 'c uint8)))
(check-equal? (send s size) 3)
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(define vs (+VersionedStruct uint8 (dictify 1 (dictify 'd s) 2 (dictify 'e s 'f s))))
(send vs force-version! 1)
(check-equal? (send vs size) 6)
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#|
(define s2 (+Struct (dictify 'a vs)))
(check-equal? (send s2 size) 6)
(define vs2 (+VersionedStruct (λ (p) 2) (dictify 1 vs 2 vs)))
(check-equal? (send vs2 size) 6)
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|#
)
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