Words to mem/file

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Fastestcodes

Joined: 13 Jun 2022
Posts: 75

Fastestcodes 11 Jul 2022, 09:10

If ax=0000 append 'cat'
if ax=0001 append 'dog'
.....
if ax=ffff append 'end'
Which is the best solution?
write sthng, file_end?
write to mem,'cat' add edi,3 write to mem 'doghouses' add edi,9 ?

11 Jul 2022, 09:10

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20700
Location: In your JS exploiting you and your system

revolution 11 Jul 2022, 09:19

Please define your criteria for "best"?

11 Jul 2022, 09:19

Fastestcodes

Joined: 13 Jun 2022
Posts: 75

Fastestcodes 11 Jul 2022, 10:16

Small
Fast.

11 Jul 2022, 10:16

macomics

Joined: 26 Jan 2021
Posts: 1179
Location: Russia

macomics 11 Jul 2022, 10:31

Code:

; switch 0 .. 65535
        mov si, ax
        add si, si
        jc @f
        mov ds, word [fs:si] ; 64 kb segment
        jmp next

@@:
        mov ds, word [gs:si] ; 64 kb segment

next:
; append word:
;   align 16
;   db 3, 'cat'
;   align 16
;   db 3, 'dog'
; ...
;   align 16
;   db 3, 'end'
        pushf
        cld
        xor si, si
        lods byte [si]
        movzx cx, al
  rep  movs byte [di], [si]
        popf

11 Jul 2022, 10:31

Fastestcodes

Joined: 13 Jun 2022
Posts: 75

Fastestcodes 11 Jul 2022, 15:09

Thx!I will try.
mov dword[edi],'dogs'
add edi,4
mov dword[edi],'cats'
mm0 and xmm0 doesnt work with 'text' Sad

11 Jul 2022, 15:09

Roman

Joined: 21 Apr 2012
Posts: 1978

Roman 11 Jul 2022, 17:08

Quote:

rep movs byte [di], [si]

Weird !
Its equal:
rep movsb

11 Jul 2022, 17:08

Fastestcodes

Joined: 13 Jun 2022
Posts: 75

Fastestcodes 11 Jul 2022, 18:29

mov dword[edi],'sedi'
mov dword[eax],'seax'
mov dword[ebx],'sebx'
mov dword[ecx],'secx'
mov dword[edx],'sedx'
mov dword[esi],'sesi'
mov dword[ebp],'sebp'
add edi,28

11 Jul 2022, 18:29

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20700
Location: In your JS exploiting you and your system

revolution 11 Jul 2022, 19:10

Fastestcodes wrote:

Small
Fast.

There is no objective measure of "fast". It depends upon the circumstances of it's execution.

Combining "small" with "fast" will lead to contradictions. You have to choose one that outweighs the other. Or you need to define a formula or function that combines the two in some way that achieves your goal.

"Small" is by far the easiest criterion to work with. I'd suggest you drop the "fast" criterion. It is the hardest to define and measure.

11 Jul 2022, 19:10

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