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Quick Search Algorithm:simplification of the Boyer-Moore alg

Cheat Engine Forum Index -> General programming

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Alice0725
Expert Cheater

Reputation: 11

Joined: 24 Jul 2012
Posts: 145

Posted: Wed Nov 28, 2012 6:16 am Post subject: Quick Search Algorithm:simplification of the Boyer-Moore alg

It's really a very quick search algorithm for simple aobscan.

Anyone know an other better quick search algorithm ?

http://www-igm.univ-mlv.fr/~lecroq/string/node19.html#SECTION00190

Code:

{
Quick Search Algorithm:
1.See QSA in http://www-igm.univ-mlv.fr/~lecroq/string/node19.html#SECTION00190
2.Add wildcards support.wildcard=$0100;.
}
function PreQsBc(aob:PWord;aobSize:integer):TIntegers;
const
ASIZE=256; //yes,a byte.
var
shift:TIntegers;
i,wcshift:integer;
wildcard:boolean=false;
begin
setlength(shift,ASIZE);
for i:=0 to ASIZE-1 do
   shift[i]:= aobSize+1;

for i:=0 to aobSize-1 do
begin
   if (aob[i] <> $0100) then
begin
Shift[aob[i]]:=aobSize-i;
end else
begin
      wildcard:=true;
      wcshift:=aobsize-i;
   end;
end;

if(wildcard=true)then
   for i:=0 to ASIZE-1 do
         if Shift[i]>wcshift then
Shift[i]:=wcshift;

Exit(shift);
end;

function QS(aob:PWord;aobSize:integer;buffer:PByte;bufferSize:integer;Shift:PInteger):integer;
var
i:integer = 0;
j:integer = 0;
begin
result := -1;
while j <= bufferSize-aobSize do
begin
   for i:=0 to (aobSize-1) do
   begin
      if(aob[i]=$0100)or(aob[i]=buffer[i+j])
      then continue
else break;
   end;

   if i+1=aobSize then
   begin
result := j;
      exit;
   end else
   begin
         j:= j+shift[Buffer[j+aobSize]];
   end;
end; //end of while
end;

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