clear string

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jacko221

Joined: 12 Nov 2005
Posts: 22

jacko221 14 Oct 2006, 14:15

Is there anyway to clear a string/buffer in my code?
For example if i define:
buffer db ?
and it gets filled with data in my code... but later i want to clear it.
How would i go about doing such a thing?
All help is appreciated Smile

Thanks, Jack

14 Oct 2006, 14:15

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20451
Location: In your JS exploiting you and your system

revolution 14 Oct 2006, 14:39

jacko221 wrote:

i want to clear it.
How would i go about doing such a thing?

like this:

Code:

mov [buffer],0

But, are you sure you want a string buffer to be one byte long? Perhaps you want:

Code:

buffer rb 1024

Then you can use something like this to clear it:

Code:

mov edi,buffer
mov ecx,1024/4
xor eax,eax
rep stosd

Last edited by revolution on 14 Oct 2006, 14:54; edited 1 time in total

14 Oct 2006, 14:39

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 14 Oct 2006, 14:45

if you mean filling with zeroes, it's:

Code:

cld
mov edi, buffer
mov ecx, size_of_buffer
mov al, 0
rep stosb

14 Oct 2006, 14:45

smiddy

Joined: 31 Oct 2004
Posts: 557

smiddy 14 Oct 2006, 17:09

Both vid and revolution are correct, however I will point out, you need to ensure that ES and DS are in the same segment/selector as the buffer, otherwise you'll put them zeros into space you may not want them to go.

14 Oct 2006, 17:09

jacko221

Joined: 12 Nov 2005
Posts: 22

jacko221 15 Oct 2006, 03:32

thanks for all your help Very Happy

15 Oct 2006, 03:32

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