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40 lines
1.3 KiB
Racket
40 lines
1.3 KiB
Racket
#lang racket/base
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(require racket/class "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 x:buffer%
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(class x:enobase%
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(super-new)
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(init-field [(@len len)])
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(unless (length-resolvable? @len)
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(raise-argument-error '+xbuffer "resolvable length" @len))
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(define/augment (x:decode port parent)
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(define len (resolve-length @len port #:parent parent))
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(read-bytes len))
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(define/augment (x:encode buf port [parent #f])
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(unless (bytes? buf)
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(raise-argument-error 'xbuffer-encode "bytes" buf))
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(when (xint? @len)
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(send @len x:encode (bytes-length buf) port))
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(write-bytes buf port))
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(define/augment (x:size [val #f] [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 @len val #:parent parent)))))
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(define (x:buffer [len-arg #f]
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#:length [len-kwarg #f]
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#:pre-encode [pre-proc #f]
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#:post-decode [post-proc #f])
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(define len (or len-arg len-kwarg #xffff))
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(new (generate-subclass x:buffer% pre-proc post-proc) [len len])) |