Improvement of function TCustomApplication.FindOptionIndex
lazarus / 64-FPC development

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lagprogramming · 2023-10-06 11:29

packages/fcl-base/src/custapp.pp has
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
TCustomApplication.FindOptionIndex(const S: String;  var Longopt:
Boolean; StartAt : Integer = -1): Integer; Var  SO,O : String;  I,P :
Integer; begin  If Not CaseSensitiveOptions then    SO:=UpperCase(S) 
else    SO:=S;  Result:=-1;  I:=StartAt;  if (I=-1) then   
I:=ParamCount;  While (Result=-1) and (I>0) do    begin   
O:=Params[i];    // - must be seen as an option value    If
(Length(O)>1) and (O[1]=FOptionChar) then      begin     
Delete(O,1,1);      LongOpt:=(Length(O)>0) and (O[1]=FOptionChar);   
 If LongOpt then        begin        Delete(O,1,1);       
P:=Pos('=',O);        If (P<>0) then          O:=Copy(O,1,P-1);      
end;      If Not CaseSensitiveOptions then        O:=UpperCase(O);   
 If (O=SO) then        Result:=i;      end;    Dec(i);    end;end;
1/4 The following lines contain a useless condition
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i     If
(Length(O)>1) and (O[1]=FOptionChar) then      begin     
Delete(O,1,1);      LongOpt:=(Length(O)>0) and (O[1]=FOptionChar);The
condition (Length(O)>0) is always true because before deleting the
first character using "Delete(O,1,1);" the length of variable O was at
least 2(due to the "If (Length(O)>1)" condition).
So, "LongOpt:=(Length(O)>0) and (O[1]=FOptionChar);" has been replaced
with "LongOpt:=(O[1]=FOptionChar);".

2/4 After that, "If (P<>0) then O:=Copy(O,1,P-1);" has been replaced
with "If P<>0 then SetLength(O,P-1);".

3/4 A -1 value is assigned to Result prior to the while loop and
inside the loop the only place the Result value is modified is at the
"Result:=i;" assignment. At the "Result:=i;" assignment, the value of
variable I is guaranteed to be greater than zero due to the existence
of the I>0 condition at the while loop. So, once we assign the value
of I to Result, we can simply exit the routine because there's nothing
else to be done.
So, "While (Result=-1) and (I>0) do" has been changed to "While I>0
do" by also changing "If (O=SO) then Result:=i;" with "If O=SO then
Exit(I);".

4/4 When using a long option the code calls Delete(O,1,1) twice, which
is a waste. It would have been nice to use a single
Delete(O,1,1+ord(LongOpt)) call but according to a forum topic,
optimizations using ord in order to get 0, 1 and -1 or not(0) values
are not guaranteed for any targeted architecture. It's a programming
practice without a documented support so the code had to be modified
using the classic approach from:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
Delete(O,1,1);LongOpt:=(O[1]=FOptionChar);If LongOpt then  begin 
Delete(O,1,1);  P:=Pos('=',O);  If P<>0 then  SetLength(O,P-1); 
end;to
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
LongOpt:=(O[2]=FOptionChar);If LongOpt then  begin  Delete(O,1,2); 
P:=Pos('=',O);  If P<>0 then    SetLength(O,P-1);  endelse 
Delete(O,1,1);
In the end, the function becomes
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
TCustomApplication.FindOptionIndex(const S: String;  var Longopt:
Boolean; StartAt : Integer = -1): Integer; Var  SO,O : String;  I,P :
Integer; begin  If Not CaseSensitiveOptions then    SO:=UpperCase(S) 
else    SO:=S;  Result:=-1;  I:=StartAt;  if I=-1 then   
I:=ParamCount;  While I>0 do    begin    O:=Params[I];    // - must be
seen as an option value    If (Length(O)>1) and (O[1]=FOptionChar)
then      begin      LongOpt:=(O[2]=FOptionChar);      If LongOpt
then        begin        Delete(O,1,2); // remove the leading --
characters of the option        P:=Pos('=',O);        If P<>0 then   
     SetLength(O,P-1);        end      else        Delete(O,1,1); //
remove the leading - character of the option      If Not
CaseSensitiveOptions then        O:=UpperCase(O);      If O=SO then  
    Exit(I);      end;    Dec(I);    end;end;
A patch is attached

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AlexTP · 2023-10-06 12:04

Posted to https://gitlab.com/freepascal.org/fpc/source/-/issues/40459