@lisp Editor base64:decode

用法

建议

(defun base64:decode (str-base64 / i res lst-base64 h%)
  "Decode base64 string."
  "list of unsigned 8bit integer."
  (if (p:stringp str-base64)
    (progn (setq lst-base64 (vl-string->list "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"))
      (setq i 0)
      (setq res (quote nil))
      (setq h% 0)
      (foreach b (mapcar (quote (lambda (x)
              (vl-position x lst-base64)))
          (vl-string->list str-base64))
        (if b (cond ((= i 0)
              (setq h% b)
              (setq i 1))
            ((= i 1)
              (setq res (cons (+ (lsh h% 2)
                    (/ b 16))
                  res))
              (setq h% (logand b 15))
              (setq i 2))
            ((= i 2)
              (setq res (cons (+ (lsh h% 4)
                    (/ b 4))
                  res))
              (setq h% (logand b 2))
              (setq i 3))
            ((= i 3)
              (setq res (cons (+ (lsh h% 6)
                    b)
                  res))
              (setq h% 0)
              (setq i 0)))))
      (reverse res))))

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