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42 lines
1.3 KiB
Racket
42 lines
1.3 KiB
Racket
#lang racket/base
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(require racket/class racket/match "base.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:bytes%
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(class x:base%
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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 'x:buffer "resolvable length" @len))
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(define/augment (x:decode port parent)
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(read-bytes (resolve-length @len port parent)))
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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 'x:buffer-encode "bytes" buf))
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(when (x:int? @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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(match val
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[(? bytes?) (bytes-length val)]
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[#false (resolve-length @len val parent)]
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[_ (raise-argument-error 'x:buffer-size "bytes or #f" val)]))))
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(define (x:bytes [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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#:base-class [base-class x:bytes%])
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(define len (or len-arg len-kwarg #xffff))
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(new (generate-subclass base-class pre-proc post-proc) [len len]))
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(define x:buffer% x:bytes%)
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(define x:buffer x:bytes) |