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typesetting/pitfall/pitfall/zlib.rkt

31 lines
995 B
Racket

#lang racket/base
(provide deflate inflate)
;; see https://groups.google.com/d/topic/racket-users/3CvjHLAmwSQ/discussion
;; for discrepancies between gzip gunzip and zlib
(require (prefix-in gzip: file/gzip)
(prefix-in gunzip: file/gunzip) png-image)
(define (deflate bstr)
;; https://www.ietf.org/rfc/rfc1950.txt
(define rfc-1950-header (bytes #x78 #x9c))
(define op (open-output-bytes))
(gzip:deflate (open-input-bytes bstr) op)
(bytes-append rfc-1950-header
(get-output-bytes op)
(integer->integer-bytes (bytes-adler32 bstr) 4 #f 'want-big-endian)))
(define (inflate bstr)
(define op (open-output-bytes))
(gunzip:inflate (open-input-bytes (subbytes bstr 2)) op)
(get-output-bytes op))
(module+ test
(require rackunit)
(for ([i (in-range 100)])
(define random-bytes
(apply bytes (for/list ([bidx (in-range 100)])
(random 256))))
(check-equal? random-bytes (inflate (deflate random-bytes)))))