{%MainUnit lazfileutils.pas}


function ExpandDots(const AFilename: string): String;
//trim double path delims and expand special dirs like .. and .
var SrcPos, DestPos, l, DirStart: integer;
  c: char;
  MacroPos: LongInt;
begin
  Result:=AFilename;

  l:=length(AFilename);
  SrcPos:=1;
  DestPos:=1;


  // trim double path delimiters and special dirs . and ..
  while (SrcPos<=l) do begin
    c:=AFilename[SrcPos];
    // check for double path delims
    if (c=PathDelim) then begin
      inc(SrcPos);
      {$IFDEF Windows}
      if (DestPos>2)
      {$ELSE}
      if (DestPos>1)
      {$ENDIF}
      and (Result[DestPos-1]=PathDelim) then begin
        // skip second PathDelim
        continue;
      end;
      Result[DestPos]:=c;
      inc(DestPos);
      continue;
    end;
    // check for special dirs . and ..
    if (c='.') then begin
      if (SrcPos<l) then begin
        if (AFilename[SrcPos+1]=PathDelim)
        and ((DestPos=1) or (AFilename[SrcPos-1]=PathDelim)) then begin
          // special dir ./
          // -> skip
          inc(SrcPos,2);
          continue;
        end else if (AFilename[SrcPos+1]='.')
        and (SrcPos+1=l) or (AFilename[SrcPos+2]=PathDelim) then
        begin
          // special dir ..
          //  1. ..      -> copy
          //  2. /..     -> skip .., keep /
          //  3. C:..    -> copy
          //  4. C:\..   -> skip .., keep C:\
          //  5. \\..    -> skip .., keep \\
          //  6. xxx../..   -> copy
          //  7. xxxdir/..  -> trim dir and skip ..
          //  8. xxxdir/..  -> trim dir and skip ..
          if DestPos=1 then begin
            //  1. ..      -> copy
          end else if (DestPos=2) and (Result[1]=PathDelim) then begin
            //  2. /..     -> skip .., keep /
            inc(SrcPos,2);
            continue;
          {$IFDEF Windows}
          end else if (DestPos=3) and (Result[2]=':')
          and (Result[1] in ['a'..'z','A'..'Z']) then begin
            //  3. C:..    -> copy
          end else if (DestPos=4) and (Result[2]=':') and (Result[3]=PathDelim)
          and (Result[1] in ['a'..'z','A'..'Z']) then begin
            //  4. C:\..   -> skip .., keep C:\
            inc(SrcPos,2);
            continue;
          end else if (DestPos=3) and (Result[1]=PathDelim)
          and (Result[2]=PathDelim) then begin
            //  5. \\..    -> skip .., keep \\
            inc(SrcPos,2);
            continue;
          {$ENDIF}
          end else if (DestPos>1) and (Result[DestPos-1]=PathDelim) then begin
            if (DestPos>3)
            and (Result[DestPos-2]='.') and (Result[DestPos-3]='.')
            and ((DestPos=4) or (Result[DestPos-4]=PathDelim)) then begin
              //  6. ../..   -> copy
            end else begin
              //  7. xxxdir/..  -> trim dir and skip ..
              DirStart:=DestPos-2;
              while (DirStart>1) and (Result[DirStart-1]<>PathDelim) do
                dec(DirStart);
              MacroPos:=DirStart;
              while MacroPos<DestPos do begin
                if (Result[MacroPos]='$')
                and (Result[MacroPos+1] in ['(','a'..'z','A'..'Z']) then begin
                  // 8. directory contains a macro -> keep
                  break;
                end;
                inc(MacroPos);
              end;
              if MacroPos=DestPos then begin
                DestPos:=DirStart;
                inc(SrcPos,2);
                continue;
              end;
            end;
          end;
        end;
      end else begin
        // special dir . at end of filename
        if DestPos=1 then begin
          Result:='.';
          exit;
        end else begin
          // skip
          break;
        end;
      end;
    end;
    // copy directory
    repeat
      Result[DestPos]:=c;
      inc(DestPos);
      inc(SrcPos);
      if (SrcPos>l) then break;
      c:=AFilename[SrcPos];
      if c=PathDelim then break;
    until false;
  end;
  // trim result
  if DestPos<=length(AFilename) then
    SetLength(Result,DestPos-1);
end;

function FilenameIsWinAbsolute(const TheFilename: string): boolean;
begin
  Result:=((length(TheFilename)>=3) and
           (TheFilename[1] in ['A'..'Z','a'..'z']) and (TheFilename[2]=':')  and (TheFilename[3]='\'))
      or ((length(TheFilename)>=2) and (TheFilename[1]='\') and (TheFilename[2]='\'))
      ;
end;

function FilenameIsUnixAbsolute(const TheFilename: string): boolean;
begin
  Result:=(TheFilename<>'') and (TheFilename[1]='/');
end;