custom sort method in Delphi to sort list of strings

Question

I am trying to sort a list of files (they are stored as list of strings) in Delphi whose names look like below

a_1.xml
a_20.xml
a_10.xml
a_2.XML

when i use quick sort to sort the file names, it sorts the file names as below

a_1.xml
a_10.xml
a_2.xml
a_20.XML

But, I want the file names to be sorted in the below fashion

a_1.xml
a_2.xml
a_10.xml
a_20.XML

Any help will be greatly appreciated.

Answer 1

You can use the same compare function that Explorer uses, namely StrCmpLogicalW.

function StrCmpLogicalW(psz1, psz2: PWideChar): Integer; stdcall;
  external 'shlwapi.dll';

function StrCmpLogical(const s1, s2: string): Integer;
begin
  Result := StrCmpLogicalW(PChar(s1), PChar(s2));
end;

If you have your strings in a TStringList instance then you can use its CustomSort method. This expects a compare function of this form:

TStringListSortCompare = function(List: TStringList; 
  Index1, Index2: Integer): Integer;

So, feed CustomSort this function:

function StringListCompareLogical(List: TStringList; 
  Index1, Index2: Integer): Integer;
begin
  Result := StrCmpLogical(List[Index1], List[Index2]);
end;