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#lang racket/base
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(require "helper.rkt" "util.rkt" "number.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/Buffer.coffee
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|#
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(define/post-decode (xbuffer-decode xb [port-arg (current-input-port)] #:parent [parent #f])
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(define port (->input-port port-arg))
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(parameterize ([current-input-port port])
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(define decoded-len (resolve-length (xbuffer-len xb) #:parent parent))
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(read-bytes decoded-len)))
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(define/pre-encode (xbuffer-encode xb buf [port-arg (current-output-port)] #:parent [parent #f])
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(define port (if (output-port? port-arg) port-arg (open-output-bytes)))
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(parameterize ([current-output-port port])
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(unless (bytes? buf)
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(raise-argument-error 'xbuffer-encode "bytes" buf))
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(when (xint? (xbuffer-len xb))
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(encode (xbuffer-len xb) (bytes-length buf)))
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(write-bytes buf)
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(unless port-arg (get-output-bytes port))))
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(define/finalize-size (xbuffer-size xb [val #f] #:parent [parent #f])
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(when val (unless (bytes? val)
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(raise-argument-error 'xbuffer-size "bytes" val)))
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(if (bytes? val)
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(bytes-length val)
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(resolve-length (xbuffer-len xb) val #:parent parent)))
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(struct xbuffer xbase (len) #:transparent
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#:methods gen:xenomorphic
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[(define decode xbuffer-decode)
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(define encode xbuffer-encode)
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(define size xbuffer-size)])
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(define (+xbuffer [len-arg #f]
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#:length [len-kwarg #f])
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(define len (or len-arg len-kwarg #xffff))
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(unless (length-resolvable? len)
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(raise-argument-error '+xbuffer "resolvable length" len))
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(xbuffer len)) |