25 Feb
2008
25 Feb
'08
7:29 p.m.
Chuck Guzis wrote:
Okay, folks--anyone got a shorter sans-jump one? One
that perhaps
doesn't require an extra register? How about one that uses a DAA to
do something sneaky?
Although it's the other way round, this is one of my top five favorite
gems of all time:
; input:
; al = single hex digit
;
; output:
; al = single ASCII digit
;
; destroys:
; flags
;
cmp al,10 ; if x < 10, set CF = 1
sbb al,69h ; 0-9: 96h .. 9Fh, A-F: A1h..A6h
das ; 0-9: subtr. 66h -> 30h-39h,
; A-F: subtr. 60h -> 41h..46h
Using the above as a basis for ascii-to-hex is left as an exercise for
Chuc^H^H^H^Hthe reader.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/