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#lang racket/base
(provide sha1
sha1-bytes
bytes->hex-string
hex-string->bytes)
(define (sha1 in [start 0] [end #f])
(bytes->hex-string (sha1-bytes in start end)))
(define (bytes->hex-string bstr)
(let* ([len (bytes-length bstr)]
[bstr2 (make-bytes (* len 2))]
[digit
(lambda (v)
(if (v . < . 10)
(+ v (char->integer #\0))
(+ v (- (char->integer #\a) 10))))])
(for ([i (in-range len)])
(let ([c (bytes-ref bstr i)])
(bytes-set! bstr2 (* 2 i) (digit (arithmetic-shift c -4)))
(bytes-set! bstr2 (+ (* 2 i) 1) (digit (bitwise-and c #xF)))))
(bytes->string/latin-1 bstr2)))
(define (hex-string->bytes s)
(unless (and (string? s) (regexp-match? #px"^([[:xdigit:]]{2})*$" s))
(raise-argument-error 'hex-string->bytes
"(and/c string? #px\"^([[:xdigit:]]{2})*$\")" s))
(define (hex-char->int c)
(cond ((char<=? #\0 c #\9) (- (char->integer c) (char->integer #\0)))
((char<=? #\a c #\f) (+ 10 (- (char->integer c) (char->integer #\a))))
((char<=? #\A c #\F) (+ 10 (- (char->integer c) (char->integer #\A))))))
(define bsize (/ (string-length s) 2))
(define b (make-bytes bsize))
(for ((i (in-range bsize)))
(define high (hex-char->int (string-ref s (+ i i))))
(define low (hex-char->int (string-ref s (+ i i 1))))
(bytes-set! b i (+ (arithmetic-shift high 4) low)))
b)
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