anchor.diff:  
           {if it's as valid a tail as we can check here...}
           CommentLen := -Offset - (TestPos - Buffer + sizeof(TailRec));
  -        if (TailRec.trLen <= CommentLen) then begin
  +        if (TailRec.CommentLength <= CommentLen) then begin
   
             {calculate its position and exit}
             Result := Result + (TestPos - Buffer);
  
positive.code:   Result := aStream.Seek(-sizeof(TailRec), soEnd);
    if (Result >= 0) then begin
      aStream.ReadBuffer(TailRec, sizeof(TailRec));
      if (TailRec.trSig = Ab_ZipEndCentralDirectorySignature) and
         (TailRec.trLen = 0) then begin
        aStream.Seek(Result, soBeginning);
        Exit;
      end;
  
negative.code: function VerifyZip(Strm : TStream) : TAbArchiveType;
  { determine if stream appears to be in PkZip format }
  var
    Footer       : TAbZipEndOfCentralDirectoryRecord;
    Sig          : LongInt;
    TailPosition : int64;
    StartPos     : int64;
  