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Allegro CL version 10.0
Unrevised from 9.0 to 10.0.
9.0 version


Arguments: context &key return

You may need to evaluate (require :digest) to load the digest code before calling this function.

Compute and return the hash from context, in a format determined by the return keyword argument. digest-init returns a context (and you specify the hashing type in that call).

return can be one of the following values:

cl-user(4): (setq c (digest-init 'md5))
#(1 35 69 103 137 171 205 239 254 220 ...)
cl-user(5): (digest-update c "foo")
cl-user(6): (digest-final c :return :usb8)
#(172 189 24 219 76 194 248 92 237 239 ...)

;;  Potential problem with :return :integer (or :return unspecified
;;  as the default is :integer). The call is to DIGEST-FILE which calls
;;  DIGEST-FINAL and returns the value MD5-FINAL returns.
;;  Here we get the md5 value in a shell:
%  openssl dgst -md5 -hex cmp05-optdialog.jpg
MD5(cmp05-optdialog.jpg)= 03c6f3f0ede5188ac49c30e11e7afa4e

;; Now we get it with DIGEST-FILE:
cl-user(17): (digest-file 'md5 "~/cmp05-optdialog.jpg")
cl-user(18): (format t "~x" *)

;; Note the hex values are the same but the leading 0 is not printed
;; by Lisp, which is dealing with the value as an integer. The leading
;; 0 is preserved when the :return is :hex:
cl-user(21): (digest-file 'md5 "~/cmp05-optdialog.jpg" :return :hex)

See MD5, SHA*, HMAC, RC4, and other message digest support in miscellaneous.htm.

Copyright (c) 1998-2016, Franz Inc. Oakland, CA., USA. All rights reserved.
This page was not revised from the 9.0 page.
Created 2015.5.21.

Allegro CL version 10.0
Unrevised from 9.0 to 10.0.
9.0 version