[aleksnine]

нашел решение

Код:

function GetHttpFileSize(const URL:string):Int64;
var
  hSession,hRequest:Pointer;
  lpBuf:array[0..30] of Char;
  dwBufLen:DWORD;
begin
  hSession:=InternetOpen(nil,INTERNET_OPEN_TYPE_PRECONFIG,nil,nil,0);
  hRequest:=InternetOpenUrl(hSession,PChar(URL),nil,0,0,0);
  dwBufLen:=SizeOf(lpBuf);
  if not HttpQueryInfo(hRequest,HTTP_QUERY_CONTENT_LENGTH,@lpBuf,dwBufLen,PDWORD(nil)^) then
    Result:=-1
  else
    Result:=StrToInt64Def(lpBuf,-1);
  InternetCloseHandle(hRequest);
  InternetCloseHandle(hSession);
end;