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codes as follows:
------------------------------------------------------------------------------------
  Jmp CodeStart
CRITICALBEGIN:
    HashData1    dd    05d56345ch
    HashData2    dd    ????
    HashData3    dd    ????
    ......
CRITICALEND:
  ......
CodeStart:
    ;assume ESI has pointed to CRITICALEND and (CRITICALEND - CRITICALBEGIN) = 5d
    ;--------------------------------------------------------------------------------
    sub esi, (CRITICALEND - CRITICALBEGIN);      81 ee 5d 00 00 00
    sub esi, low(CRITICALEND - CRITICALBEGIN);  81 ee 5d 00 00 00
    sub esi, byte(CRITICALEND - CRITICALBEGIN); 81 ee 5e(?) 00 00 00
    sub esi, 05dh;                                              83 ee 5d
    ;----------------------------------------------------------------------------------

  question1: only the codes generated by the fourth are what i want, but i don't want to sacrifice the advantage of auto-counting the length of CRITICAL data section by pre-compiler. how can i do it? ( to use 'add esi, (CRITICALBEGIN - CRITICALEND)' also generates 6 bytes)

  question2: why the codes of 'sub esi, byte(CRITICALEND - CRITICALBEGIN)'(the third sub instruction) include a 5e but 5d?

thanks.

Something very old (or very bugged), I guess  :shock:

Lava,
    The answer to your prob is easy.  You want MASM to generate the shorter 83 BYTE operand code right?  Well, that 83 instruction sign extends the immediate BYTE operand.  You don't want that to happen when your table length is greater than 7 bits, do you?  So MASM has to use the 81 DWORD operand to avoid sign extension.  Now if MASM were really smart, it would know if the byte operand was less than or equal 7 bits and use the 83 BYTE operand code.  Ratch

------------------------------
thanks.

yes, but what u posted is the reason, not the answer:)

my question is ' is masm smart enough? or how to make it smarter?'

'81 ee 5d 00 00 00' may be executed faster than 83 because of avoiding  sign extension(i guess), but how can i tell the masm: do not care the speed, make it shorter?

yes, i got it . that's why i tried 'sub esi, low(CRITICALEND - CRITICALBEGIN), but i am not sure whether the mission is possible.

if the answer is not, i'll try FASM, thank u:)

question1 answer:

sub esi,@CatStr(%(CRITICALEND-CRITICALBEGIN))

question2 answer:
"byte" by itself means no size cast, it means +1 in this case
to use size cast use "type ptr"
like for long push 0 :
  push dword ptr 0

It works very well:
    DIFF = (CRITICALEND - CRITICALBEGIN)
    IF DIFF LT 080H
        BYTE 083H, 0EEH, DIFF
    ELSE
        sub esi, DIFF
    ENDIF
-----------------------------------------------------------
hutch, ratch and other guys, thanks.

drizz:
    sub esi, @CatStr(%(CRITICALEND - CRITICALBEGIN)
the result is weird: 83 ee 6d(not 5d). i also try this:
    sub esi, @CatStr(%DIFF)
83 ee 6d appears again, why?

yes, my mistake, i assumed it was data only (hashdata1..),
if you have relocatable labels(+instructions that use it) in between it wont work.

CRITICALBEGIN1:
	jmp @1
@1:	
CRITICALEND1:
%echo @CatStr(%(CRITICALEND1-CRITICALBEGIN1))

if you use location counter $ it will work

CRITICALBEGIN2:
	jmp $+2
CRITICALEND2:
%echo @CatStr(%(CRITICALEND2-CRITICALBEGIN2))

Lava,
that's interesting, could you post all code (data) between CRITICALEND and CRITICALBEGIN?