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#lang racket/base
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(require racket/private/generic-methods
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racket/class
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"generic.rkt")
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(provide (all-defined-out))
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(struct x:ptr (type val parent) #:transparent)
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(define x:version-key 'x:version)
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(define x:start-offset-key 'x:start-offset)
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(define x:current-offset-key 'x:current-offset)
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(define x:length-key 'x:length)
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(define x:parent-key 'x:parent)
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(define x:pointer-size-key 'x:ptr-size)
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(define x:pointers-key 'x:pointers)
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(define x:pointer-offset-key 'x:ptr-offset)
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(define x:pointer-type-key 'x:ptr-type)
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(define x:val-key 'x:val)
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(define private-keys (list x:parent-key x:start-offset-key x:current-offset-key x:length-key x:pointer-size-key
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x:pointers-key x:pointer-offset-key x:pointer-type-key x:val-key))
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(define (hash-ref* d . keys)
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(for/fold ([d d])
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([k (in-list keys)])
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(hash-ref d k)))
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(define (pos p [new-pos #f])
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(when new-pos
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(file-position p new-pos))
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(file-position p))
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(define xenomorphic<%>
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(interface* ()
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([(generic-property gen:xenomorphic)
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(generic-method-table
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gen:xenomorphic
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(define (decode xo [port-arg (current-input-port)] #:parent [parent #f])
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(define port
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(cond
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[(input-port? port-arg) port-arg]
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[(bytes? port-arg) (open-input-bytes port-arg)]
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[else (raise-argument-error 'decode "byte string or input port" port-arg)]))
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(send xo decode port parent))
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(define (encode xo val [port-arg (current-output-port)]
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#:parent [parent #f])
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(define port (if (output-port? port-arg) port-arg (open-output-bytes)))
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(send xo x:encode val port parent)
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(unless port-arg (get-output-bytes port)))
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(define (size xo [val #f] #:parent [parent #f])
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(send xo x:size val parent)))])))
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(define (xenomorphic-type? x) (is-a? x xenobase%))
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(define-syntax-rule (generate-subclass CLASS PRE-ENCODE-PROC POST-DECODE-PROC)
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(cond
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[(and PRE-ENCODE-PROC POST-DECODE-PROC)
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(class CLASS
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(super-new)
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(define/override (pre-encode x) (super pre-encode (PRE-ENCODE-PROC x)))
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(define/override (post-decode x) (POST-DECODE-PROC (super post-decode x))))]
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[PRE-ENCODE-PROC
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(class CLASS
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(super-new)
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(define/override (pre-encode x) (super pre-encode (PRE-ENCODE-PROC x))))]
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[POST-DECODE-PROC
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(class CLASS
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(super-new)
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(define/override (post-decode x) (POST-DECODE-PROC (super post-decode x))))]
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[else CLASS]))
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(define xenobase%
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(class* object% (xenomorphic<%>)
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(super-new)
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(define/pubment (x:decode input-port [parent #f])
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(post-decode (inner (error 'x:decode-not-augmented) x:decode input-port parent)))
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(define/public (decode input-port [parent #f])
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(x:decode input-port parent))
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(define/pubment (x:encode val output-port [parent #f])
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(define encode-result (inner (error 'x:encode-not-augmented) x:encode (pre-encode val) output-port parent))
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(when (bytes? encode-result) (write-bytes encode-result output-port)))
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(define/pubment (x:size [val #f] [parent #f] . args)
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(define size (inner 0 x:size val parent . args))
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(unless (and (integer? size) (not (negative? size)))
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(raise-argument-error 'size "nonnegative integer" size))
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size)
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(define/public (post-decode val) val)
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(define/public (pre-encode val) val)))
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