usb8-array-to-base64-string

Arguments: usb8-array &key (wrap-at-column 52) start end

Takes the (unsigned-byte 8) array specified by the usb8-array, assumes it is a base64 encoding (with the first (index 0 or index start) element the most significant), and converts it to a base64 string. If wrap-at-column is non-nil, its value must be a positive integer and newlines are inserted in the string each time that number of characters is output. If wrap-at-column is nil, no newlines are inserted. start and end specify the portion of the usb8-array to convert. If unspecified, the whole array is converted.

In releases prior to 8.1, there was no start or end wrguments and wrap-at-column was an optional argument rather than a keyword argument. The optional argument calling sequence is still accepted though strongly discouraged. Thus (usb8-array-to-base64-string usb8-array 80) is accepted and equivalent to (usb8-array-to-base64-string usb8-array :wrap-at-column 80). If you use the optional argument calling sequence, you may not also specify values for start or end.

The function base64-string-to-usb8-array converts a base64 string (the output of this function) back to an (unsigned-byte 8) array.

Here are some examples. First we show that the first array element is the most significant (using base64-string-to-integer). Then we give a more complex example.

cl-user(2): (setq ar1 (make-array 2 :element-type '(unsigned-byte 8)
                          :initial-contents '(10 40)))
#(10 40)
cl-user(3): (setq b1 (usb8-array-to-base64-string ar1))
"Cig="
cl-user(4): (base64-string-to-integer b1)
2600  ;;  equals (+ (* 10 (expt 2 8)) 40) equals (+ 2560 40)

cl-user(5): (setq a (string-to-octets
		     (setq s
		       "
(defun deep-thought ()
  (sleep (years2secs 7500000))
  42)
")))
#(10 40 100 101 102 117 110 32 100 101 ...)
cl-user(6): (usb8-array-to-base64-string a)
"CihkZWZ1biBkZWVwLXRob3VnaHQgKCkKICAoc2xlZXAgKHllYXJz
MnNlY3MgNzUwMDAwMCkpCiAgNDIpCgA="
cl-user(7): (base64-string-to-usb8-array *)
#(10 40 100 101 102 117 110 32 100 101 ...)
cl-user(8): (setq a2 *)
#(10 40 100 101 102 117 110 32 100 101 ...)
cl-user(9): (equalp a a2)
t
cl-user(10): (octets-to-string a2)
"
(defun deep-thought ()
  (sleep (years2secs 7500000))
  42)
"
61
61

See Base64 Support in miscellaneous.htm for information on Base64 and Base64 support in Allegro CL.

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This page was not revised from the 10.0 page.
Created 2019.8.20.