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Url-encoding

Vl-url-encode-char

URL encode a single character. (slow, logically nice version).

Signature
(vl-url-encode-char x) → encoding
Arguments: x — Guard (characterp x).
Returns: encoding — Encoded version of X, in proper order.
Type (character-listp encoding).

See vl-fast-url-encode-char for an faster, array-lookup alternative.

Definitions and Theorems

Function: vl-url-encode-char

(defun vl-url-encode-char (x)
  (declare (xargs :guard (characterp x)))
  (let ((__function__ 'vl-url-encode-char))
    (declare (ignorable __function__))
    (let ((x (char-fix x)))
      (if (or (and (char<= #\A x) (char<= x #\Z))
              (and (char<= #\a x) (char<= x #\z))
              (and (char<= #\0 x) (char<= x #\9))
              (member x '(#\- #\_ #\. #\~)))
          (list x)
        (let* ((hex-code (explode-atom (char-code x) 16))
               (hex-code (if (eql (len hex-code) 1)
                             (cons #\0 hex-code)
                           hex-code)))
          (cons #\% hex-code))))))

Theorem: character-listp-of-vl-url-encode-char

(defthm character-listp-of-vl-url-encode-char
  (b* ((encoding (vl-url-encode-char x)))
    (character-listp encoding))
  :rule-classes :rewrite)

Theorem: vl-url-encode-char-of-char-fix-x

(defthm vl-url-encode-char-of-char-fix-x
  (equal (vl-url-encode-char (char-fix x))
         (vl-url-encode-char x)))

Theorem: vl-url-encode-char-chareqv-congruence-on-x

(defthm vl-url-encode-char-chareqv-congruence-on-x
  (implies (chareqv x x-equiv)
           (equal (vl-url-encode-char x)
                  (vl-url-encode-char x-equiv)))
  :rule-classes :congruence)