[CLOSED] Improvement of TFPCustomImage.FindHandlerFromExtension

[lagprogramming]

packages/fcl-image/src/fpimage.inc has the following function:

Code: Pascal  [Select][+][-]

1. class function TFPCustomImage.FindHandlerFromExtension(extension: String
2.   ): TIHData;
3. var s : string;
4.     r : integer;
5. begin
6.   if extension='' then
7.     Exit(nil);
8.   extension := lowercase (extension);
9.   if (extension <> '') and (extension[1] = '.') then
10.     delete (extension,1,1);
11.   with ImageHandlers do
12.     begin
13.       r := count-1;
14.       s := dumchar  + extension + dumchar;
15.       while (r >= 0) do
16.         begin
17.         Result := GetData(r);
18.         if (pos(s, dumchar+Result.Fextension+dumchar) <> 0) then
19.           Exit;
20.         dec (r);
21.         end;
22.     end;
23.   Result := nil;
24. end;

The patch at the end of the message changes the above code to

Code: Pascal  [Select][+][-]

1. class function TFPCustomImage.FindHandlerFromExtension(extension: String
2.   ): TIHData;
3. var s : string;
4.     r : integer;
5. begin
6.   if extension <> '' then
7.     begin
8.     extension := lowercase (extension);
9.     if extension[1] = '.' then
10.       delete (extension,1,1);
11.     with ImageHandlers do
12.       begin
13.         r := count-1;
14.         s := dumchar  + extension + dumchar;
15.         while (r >= 0) do
16.           begin
17.           Result := GetData(r);
18.           if (pos(s, dumchar+Result.Fextension+dumchar) <> 0) then
19.             Exit;
20.           dec (r);
21.           end;
22.       end;
23.     end;
24.   Result := nil;
25. end;

Code: Pascal  [Select][+][-]

1. begin
2.   if extension='' then
3.     Exit(nil);
4.   //CODE
5.   Result := nil;
6. end;

is changed to

Code: Pascal  [Select][+][-]

1. begin
2.   if extension<>'' then
3.     begin
4.     //CODE
5.     end;
6.   Result := nil;
7. end;

and after that

Code: Pascal  [Select][+][-]

1. if (extension <> '') and (extension[1] = '.') then

is replaced with

Code: Pascal  [Select][+][-]

1. if extension[1] = '.' then

The modified pascal code avoids duplicate nil assignments to function's result and also avoids the duplicate check for a nil(empty) extension variable. Obviously, the compiler produces better code for the modified pascal sources than for the original.
I've tried to keep the original code formatting style, here is the patch.

Code: Pascal  [Select][+][-]

1. diff --git a/packages/fcl-image/src/fpimage.inc b/packages/fcl-image/src/fpimage.inc
2. index 531c4ec219..b4fb9dac24 100644
3. --- a/packages/fcl-image/src/fpimage.inc
4. +++ b/packages/fcl-image/src/fpimage.inc
5. @@ -274,22 +274,23 @@ class function TFPCustomImage.FindHandlerFromExtension(extension: String
6.  var s : string;
7.      r : integer;
8.  begin
9. -  if extension='' then
10. -    Exit(nil);
11. -  extension := lowercase (extension);
12. -  if (extension <> '') and (extension[1] = '.') then
13. -    delete (extension,1,1);
14. -  with ImageHandlers do
15. +  if extension <> '' then
16.      begin
17. -      r := count-1;
18. -      s := dumchar  + extension + dumchar;
19. -      while (r >= 0) do
20. -        begin
21. -        Result := GetData(r);
22. -        if (pos(s, dumchar+Result.Fextension+dumchar) <> 0) then
23. -          Exit;
24. -        dec (r);
25. -        end;
26. +    extension := lowercase (extension);
27. +    if extension[1] = '.' then
28. +      delete (extension,1,1);
29. +    with ImageHandlers do
30. +      begin
31. +        r := count-1;
32. +        s := dumchar  + extension + dumchar;
33. +        while (r >= 0) do
34. +          begin
35. +          Result := GetData(r);
36. +          if (pos(s, dumchar+Result.Fextension+dumchar) <> 0) then
37. +            Exit;
38. +          dec (r);
39. +          end;
40. +      end;
41.      end;
42.    Result := nil;
43.  end;