sha1-final

Arguments: context &key return

Finalize and return the SHA1 hash from context in a format determined by the return keyword argument.

return can be one of the following values:

• :integer (the default): the return value is an integer of up to 160 bits representing the digest. Warning: note that an integer representation of the digest potentially loses information if the generated signature has leading octets containing only zeroes. Care should be taking when using this return type if you intend to further encode the signature (such as to a base64-encoded string). See the example below.
• :usb8: return an (unsigned-byte 8) array containing the digest.
• :hex: return a string containing the hexadecimal representation of the digest. See hex-string-to-integer.

cl-user(4): (setq c (sha1-init))
#S(excl::md-context :ctx 156672 :size 20)
cl-user(5): (sha1-update c "foo")
cl-user(6): (sha1-final c :return :usb8)
#(11 238 199 181 234 63 15 219 201 93 ...)

;;  Potential problem with :return :integer (or :return unspecified
;;  as the default is :integer). The call is to SHA1-FILE which calls
;;  SHA1-FINAL and returns the value SHA1-FINAL returns.
;;
;;  Here we get the sha1 value in a shell:
%  openssl dgst -sha1 -hex cmp05-optdialog.jpg
SHA1(cmp05-optdialog.jpg)= 9bd9c1bbd45ec006e281cf056227898c5996bb87

;; Now we get it with SHA1-FILE:
cl-user(17): (sha1-file "~/cmp05-optdialog.jpg")
889749707772052021200163874326026364472582912903
cl-user(18): (format t "~x" *)
9bd9c1bbd45ec006e281cf056227898c5996bb87
nil
cl-user(19): 

;; 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): (sha1-file "~/cmp05-optdialog.jpg" :return :hex)
"9bd9c1bbd45ec006e281cf056227898c5996bb87"
cl-user(22): 

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

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