Strange behaviour when simply adding strings in Lazarus - FreePascal
- by linkcharger
The program has several "encryption" algorithms. This one should blockwise reverse the input. "He|ll|o " becomes "o |ll|He" (block length of 2).
I add two strings, in this case appending the result string to the current "block" string and making that the result. When I add the result first and then the block it works fine and gives me back the original string. But when i try to reverse the order it just gives me the the last "block".
Several other functions that are used for "rotation" are above.
//amount of blocks
function amBl(i1:integer;i2:integer):integer;
begin
if (i1 mod i2) <> 0 then result := (i1 div i2) else result := (i1 div i2) - 1;
end;
//calculation of block length
function calcBl(keyStr:string):integer;
var i:integer;
begin
result := 0;
for i := 1 to Length(keyStr) do
begin
result := (result + ord(keyStr[i])) mod 5;
result := result + 2;
end;
end;
//desperate try to add strings
function append(s1,s2:string):string;
begin
insert(s2,s1,Length(s1)+1);
result := s1;
end;
function rotation(inStr,keyStr:string):string;
var //array of chars -> string
block,temp:string;
//position in block variable
posB:integer;
//block length and block count variable
bl, bc:integer;
//null character as placeholder
n : ansiChar;
begin
//calculating block length 2..6
bl := calcBl(keyStr);
setLength(block,bl);
result := '';
temp := '';
{n := #00;}
for bc := 0 to amBl(Length(inStr),bl) do
begin
//filling block with chars starting from back of virtual block (in inStr)
for posB := 1 to bl do
begin
block[posB] := inStr[bc * bl + posB];
{if inStr[bc * bl + posB] = ' ' then block[posB] := n;}
end;
//adding the block in front of the existing result string
temp := result;
result := block + temp;
//result := append(block,temp);
//result := concat(block,temp);
end;
end;
(full code http://pastebin.com/6Uarerhk)
After all the loops "result" has the right value, but in the last step (between "result := block + temp" and the "end;" of the function) "block" replaces the content of "result" with itself completely, it doesn't add result at the end anymore.
And as you can see I even used a temp variable to try to work around that.. doesnt change anything though.
