FunctionPackage: exclToCDocOverviewCGDocRelNotesFAQIndexPermutedIndex
Allegro CL version 10.1
Unrevised from 10.0 to 10.1.
10.0 version


Arguments: context &key return

Finalize and return the SHA256 hash from context in a format determined by the return keyword argument.

return can be one of the following values:

cl-user(4): (setq c (sha256-init))
#S(excl::md-context :ctx 9183616 :size 32)
cl-user(5): (sha256-update c "foo")
cl-user(6): (sha256-final c :return :usb8)
#(44 38 180 107 104 255 198 143 249 155 ...)

;;  Potential problem with :return :integer (or :return unspecified
;;  as the default is :integer). The call is to SHA256-FILE which calls
;;  SHA256-FINAL and returns the value SHA256-FINAL returns.
;;  Here we get the sha256 value in a shell:
% openssl dgst -sha256 -hex tab-order.jpg 
SHA256(tab-order.jpg)= 079331d027a95cc63d1466fdf859e0c6b83532199e1c935f30a658bf8e5f8e29

;; Now we get it with SHA256-FILE:
cl-user(17): (sha256-file "~/tab-order.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): (sha256-file "~/tab-order.jpg" :return :hex)

See MD*, SHA*, HMAC, and other message digest support in miscellaneous.htm. See also digest-final.

Copyright (c) 1998-2022, Franz Inc. Lafayette, CA., USA. All rights reserved.
This page was not revised from the 10.0 page.
Created 2019.8.20.

Allegro CL version 10.1
Unrevised from 10.0 to 10.1.
10.0 version