Re: Searching for string problems

["Randy.Dunlap" <rddunlap@osdl.org>]

On Wed, 23 Apr 2003 22:48:35 +0300 Andrew Kirilenko <icedank@gmx.net> wrote:

| Hello!
| 
| Big thanks to all of you. Now I'm starting to understand how it's working. 
| Here is current version of my code:
| 
| -->
|        jmp         cl_start
| cl_id_str:      .string "STRING"
| cl_start:
|         cld
|         movw    %cs, %ax
|         movw    %ax, %ds
|         movw    $0xe000, %ax
|         movw    %ax, %es
|         movb    $0, %al
|         xor         %bx, %bx  # start of segment
| cl_compare:
|         movw    $cl_id_str, %si
|         movw    $cl_start, %cx
|         subw    %si, %cx
|         decw    %cx
|         movw    %bx, %di
|         repz    cmpsb
|         je      cl_compare_done_good
|         incw    %bx
|         cmpw    $0xffff, %bx  # are we at the end of segment
|         je      cl_compare_done
|         jmp     cl_compare
| cl_compare_done_good:
|        movb $1, %al
| cl_compare_done:

# here the code needs to do something like this,
# to check the second 64 KB block of memory:
	movw	%es, %bx
	cmpw	%bx, $0xe000
	je	all_done
	movw	$0xf000, %bx
	movw	%bx, %es
	xor	%bx, %bx
	jmp	cl_compare


| <--
| 
| And this code won't work as well :(

Do you understand x86 real-mode segment registers?
They can only address a "segment" of 64 KB (roughly).

| Unfortunately, I can't start DOS and check, cause there is no video and 
| keyboard controller on that PC.

oh yes.

--
~Randy