XPost: comp.os.msdos.programmer, alt.lang.asm
From: admin@nospicedham.127.0.0.1
On Fri, 27 Jan 2023 13:30:13 +0000
"Kerr-Mudd, John" wrote:
> On Fri, 27 Jan 2023 09:57:22 +0000
> "Kerr-Mudd, John" wrote:
>
> > On Wed, 25 Jan 2023 17:02:43 +0000
> > "Kerr-Mudd, John" wrote:
> >
> []
> > > > Kerr-Mudd, John wrote:
> > > > > Finally, a rot13 program for DOS that's smaller than the standard
version
> > > > > with jumps:
> > > > >
[]
> 'Better' still use C3 (embedded 'ret') to reduce prog to 45 bytes.
[]
One that works even if the rot amount isn't 13 (ie the older version
didn't!) also 45 bytes:
->u 100 l2D
16AD:0100 BA E6 0D mov dx,0DE6
16AD:0103 B4 3F mov ah,3F
16AD:0105 B5 C3 mov ch,C3
16AD:0107 CD 21 int 21
16AD:0109 91 xchg ax,cx
16AD:010A E3 FA jcxzw 0106
16AD:010C 89 D6 mov si,dx
16AD:010E 51 push cx
16AD:010F AC lodsb
16AD:0110 24 DF and al,DF
16AD:0112 2C 41 sub al,41
16AD:0114 2C 1A sub al,1A
16AD:0116 18 E4 sbb ah,ah
16AD:0118 00 F0 add al,dh
16AD:011A D6 salc
16AD:011B 21 D0 and ax,dx
16AD:011D 00 E0 add al,ah
16AD:011F 00 64 FF add [si-01],ah
16AD:0122 E2 EB loopw 010F
16AD:0124 59 pop cx
16AD:0125 43 inc bx
16AD:0126 B4 40 mov ah,40
16AD:0128 CD 21 int 21
16AD:012A 4B dec bx
16AD:012B EB D6 jmp 0103
-> d 100 l2D
16AD:0100 BA E6 0D B4-3F B5 C3 CD-21 91 E3 FA-89 D6 51 AC ....?...!.....Q.
16AD:0110 24 DF 2C 41-2C 1A 18 E4-00 F0 D6 21-D0 00 E0 00 $.,A,......!....
16AD:0120 64-FF E2 EB 59-43 B4 40 CD-21 4B EB D6 d...YC.@.!K..
-> q
And a version that allows the rot amount as a parameter in 64 bytes:
example usage:
rot 3u 100 l40
16AD:0100 BA E6 0D mov dx,0DE6
16AD:0103 BE 82 00 mov si,0082
16AD:0106 AD lodsw
16AD:0107 2D 30 30 sub ax,3030
16AD:010A 72 04 jb 0110
16AD:010C 86 E0 xchg ah,al
16AD:010E D5 0A aad 0A
16AD:0110 3C 00 cmp al,00
16AD:0112 72 02 jb 0116
16AD:0114 88 C6 mov dh,al
16AD:0116 B4 3F mov ah,3F
16AD:0118 B5 C3 mov ch,C3
16AD:011A CD 21 int 21
16AD:011C 91 xchg ax,cx
16AD:011D E3 FA jcxzw 0119
16AD:011F 89 D6 mov si,dx
16AD:0121 51 push cx
16AD:0122 AC lodsb
16AD:0123 24 DF and al,DF
16AD:0125 2C 41 sub al,41
16AD:0127 2C 1A sub al,1A
16AD:0129 18 E4 sbb ah,ah
16AD:012B 00 F0 add al,dh
16AD:012D D6 salc
16AD:012E 21 D0 and ax,dx
16AD:0130 00 E0 add al,ah
16AD:0132 00 44 FF add [si-01],al
16AD:0135 E2 EB loopw 0122
16AD:0137 59 pop cx
16AD:0138 43 inc bx
16AD:0139 B4 40 mov ah,40
16AD:013B CD 21 int 21
16AD:013D 4B dec bx
16AD:013E EB D6 jmp 0116
-> d 100 l40
16AD:0100 BA E6 0D BE-82 00 AD 2D-30 30 72 04-86 E0 D5 0A .......-00r.....
16AD:0110 3C 00 72 02-88 C6 B4 3F-B5 C3 CD 21-91 E3 FA 89 <.r....?...!....
16AD:0120 D6 51 AC 24-DF 2C 41 2C-1A 18 E4 00-F0 D6 21 D0 .Q.$.,A,......!.
16AD:0130 00 E0 00 44-FF E2 EB 59-43 B4 40 CD-21 4B EB D6 ...D...YC.@.!K..
-> q
--
Bah, and indeed Humbug.
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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