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tonyg/racket-bitsyntax

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racket-bitsyntax

Adds library support for slices and splices of byte-vectors to Racket, and adds syntax for pattern-matching such bit-strings, inspired by Erlang's binary pattern-matching:

Documentation

A rendered version of the documentation for this library is available via Github Pages:

Example

Here's a Racket equivalent of the example given in the Erlang documentation:

(define IP-VERSION 4)
(define IP-MINIMUM-HEADER-LENGTH 5)
(bit-string-case datagram
  ([ (= IP-VERSION :: bits 4)
     (header-length :: bits 4)
     service-type
     (total-length :: bits 16)
     (id :: bits 16)
     (flags :: bits 3)
     (fragment-offset :: bits 13)
     ttl
     protocol
     (header-checksum :: bits 16)
     (source-ip :: bits 32)
     (destination-ip :: bits 32)
     (rest :: binary) ]
   (when (and (>= header-length 5)
              (>= (bit-string-length datagram) (* header-length 4))))
   (let ((options-length (* 4 (- header-length IP-MINIMUM-HEADER-LENGTH))))
     (bit-string-case rest
       ([ (opts :: binary bytes options-length)
          (data :: binary) ]
        'datagram-valid))))
  [else
   'datagram-not-valid])