delphi 判断是否是下载链接的函数

function IsProtocolSupported(const url: string): boolean;

const

  Protocols: array [1..3] of string =

    ('http:', 'https:', 'magnet:');

var

  i: integer;

  s: string;

begin

  s:=AnsiLowerCase(url);

  for i:=Low(Protocols) to High(Protocols) do

    if Copy(s, 1, Length(Protocols[i])) = Protocols[i] then begin

      Result:=True;

      exit;

    end;

  Result:=False;

end;