[racket-dev] hex decoding?

Sorry all I am saying the creator of db/private/mysql/connection.rkt didn't anticipate your needs and kept the function private. 

If you want to submit a pull request to move this function to db or db/base (including an appropriate provide), please do so. 




On Jun 11, 2013, at 4:41 PM, David Vanderson wrote:

> On 06/11/2013 04:33 PM, Matthias Felleisen wrote:
>> 
>>  db/private/mysql/connection.rkt does not export the function, otherwise you could.
> I don't understand this.  I'd like to make the function available to users somewhere - are you saying that's bad?
>> 
>> 
>> On Jun 11, 2013, at 4:26 PM, David Vanderson wrote:
>> 
>>> Thank you Stephen and Tony for your examples.  I found the following private function in db/private/mysql/connection.rkt:
>>> 
>>> (define (hex-string->bytes s)
>>>  (define (hex-digit->int c)
>>>    (let ([c (char->integer c)])
>>>      (cond [(<= (char->integer #\0) c (char->integer #\9))
>>>             (- c (char->integer #\0))]
>>>            [(<= (char->integer #\a) c (char->integer #\f))
>>>             (+ 10 (- c (char->integer #\a)))]
>>>            [(<= (char->integer #\A) c (char->integer #\F))
>>>             (+ 10 (- c (char->integer #\A)))])))
>>>  (unless (and (string? s) (even? (string-length s))
>>>               (regexp-match? #rx"[0-9a-zA-Z]*" s))
>>>    (raise-type-error 'hex-string->bytes
>>>                      "string containing an even number of hexadecimal digits" s))
>>>  (let* ([c (quotient (string-length s) 2)]
>>>         [b (make-bytes c)])
>>>    (for ([i (in-range c)])
>>>      (let ([high (hex-digit->int (string-ref s (+ i i)))]
>>>            [low  (hex-digit->int (string-ref s (+ i i 1)))])
>>>        (bytes-set! b i (+ (arithmetic-shift high 4) low))))
>>>    b))
>>> 
>>> 
>>> Can this function be exported?  I'm willing to make a patch with docs and tests - is file/sha1 the right place?
>>> 
>>> Thanks,
>>> Dave
>>> 
>>> _________________________
>>> Racket Developers list:
>>> http://lists.racket-lang.org/dev
>> 
>