cl-nixbase32 initial iteration

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No description provided.

[kisp]

go-nix/nixbase32/nixbase32.go at dev · zombiezen/go-nix
https://github.com/zombiezen/go-nix/blob/dev/nixbase32/nixbase32.go

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;; Define the alphabet used in Nix base32 encoding
(defparameter *alphabet* "0123456789abcdfghijklmnpqrsvwxyz")

;; Function to decode a nixbase32 string into bytes
(defun decode-string (s)
  (let ((dst (make-array (decoded-len (length s)))))
    (multiple-value-bind (n err)
        (decode dst (coerce s 'list))
      (subseq dst 0 n))))

;; Function to decode nixbase32 encoded data
(defun decode (dst src)
  (let ((max-dst-size (decoded-len (length src))))
    (loop for n from 0 below (length src)
          for b = (* n 5)
          for i = (floor b 8)
          for j = (mod b 8)
          for c = (elt (reverse src) n)
          for digit = (position c *alphabet*)
          do (if (null digit)
                 (return-from decode (values i (error "Decode base32: character not in Nix alphabet")))
                 (setf (aref dst i) (logior (aref dst i) (ash digit j)))
                 (let ((carry (ash digit (- 8 j))))
                   (if (< (1+ i) max-dst-size)
                       (setf (aref dst (1+ i)) (logior (aref dst (1+ i)) carry))
                       (if (plusp carry)
                           (return-from decode (values i (error "Decode base32: non-zero padding"))))))))))

;; Function to validate a nixbase32 encoded string
(defun validate-string (src)
  (let ((max-dst-size (decoded-len (length src))))
    (loop for n from 0 below (length src)
          for b = (* n 5)
          for i = (floor b 8)
          for j = (mod b 8)
          for c = (elt (reverse src) n)
          for digit = (position c *alphabet*)
          do (if (null digit)
                 (return-from validate-string (error "Decode base32: character not in Nix alphabet"))
                 (when (>= (1+ i) max-dst-size)
                   (let ((carry (ash digit (- 8 j))))
                     (when (plusp carry)
                       (return-from validate-string (error "Decode base32: non-zero padding")))))))))

;; Function to get the length in bytes of the base32 encoding
(defun encoded-len (n)
  (ceiling (* (+ (* n 8) 4) 5)))

;; Function to get the length in bytes of the decoded data
(defun decoded-len (n)
  (floor (* n 5) 8))

;; Function to encode data using nixbase32
(defun encode (dst src)
  (let ((n (encoded-len (length src))))
    (dotimes (n (- n 1) dst)
      (let* ((b (* n 5))
             (i (floor b 8))
             (j (mod b 8))
             (c (ash (aref src i) (- j))))
        (when (< (1+ i) (length src))
          (setf c (logior c (ash (aref src (1+ i)) (- 8 j)))))
        (push (aref *alphabet* (logand c #x1f)) dst)))))

;; Function to encode data to nixbase32 string
(defun encode-to-string (src)
  (let ((n (encoded-len (length src)))
        (result ""))
    (dotimes (n (- n 1) result)
      (let* ((b (* n 5))
             (i (floor b 8))
             (j (mod b 8))
             (c (ash (aref src i) (- j))))
        (when (< (1+ i) (length src))
          (setf c (logior c (ash (aref src (1+ i)) (- 8 j)))))
        (setf result (concatenate 'string (string (aref *alphabet* (logand c #x1f))) result))))))

;; Predicate to check if a byte is part of the nixbase32 alphabet
(defun is-nixbase32-char-p (c)
  (or (and (char<= #\0 c #\9))
      (and (char<= #\a c #\z)
           (not (member c '(#\e #\o #\u #\t))))))

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nix-prefetch-url - Nix Reference Manual
https://nixos.org/manual/nix/stable/command-ref/nix-prefetch-url

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13:48 $ nix-prefetch-url http://pauldist.kisp.in/archive/hgetopt-0.0.4.tgz
path is '/nix/store/74l2bfic29rbl14wnhdwdrxm84v8qqxs-hgetopt-0.0.4.tgz'
1ak0qjw1r1idnv0847fvyj3jsd3m7z8674c41p76hr36d98n9wk2

13:48 $ nix-hash --flat --type sha256 /nix/store/74l2bfic29rbl14wnhdwdrxm84v8qqxs-hgetopt-0.0.4.tgz
62f264516a666468ce0d849163d03f75342d87f4db1d82c0b62d861cb8c460aa

13:48 $ nix-hash --flat --type sha256 --base32 /nix/store/74l2bfic29rbl14wnhdwdrxm84v8qqxs-hgetopt-0.0.4.tgz
1ak0qjw1r1idnv0847fvyj3jsd3m7z8674c41p76hr36d98n9wk2

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RFC 4648 - The Base16, Base32, and Base64 Data Encodings
https://datatracker.ietf.org/doc/html/rfc4648#section-6

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Document that base32 hashes are not the base32 everyone expects · Issue #4354 · NixOS/nix
NixOS/nix#4354