(Delphi ActiveX) Punycode Encoding / Decoding

Punycode is an encoding standard for representing Unicode characters using only the 7bit us-ascii characters that are permitted in network host names. Punycode is used for internationalized domain names -- i.e. IDN or IDNA (Internationalizing Domain Names in Applications).

Punycode is defined in RFC 3492. Converting to/from punycode does not include the "xn--" prefix. The "xn--" prefix is to signify that punycode follows. For example, the string " café.com" is converted to "caf-dma.com" in punycode. The punycode domain name is "xn--caf-dma.com".

Converting an email address to punycode would be as follows. Suppose the email address is "coffee@café.com". The punycode representation is "coffee@xn--caf-dma.com". The RFC 3492 punycode representation of "café.com" is simply "caf-dma.com", but the punycode domain name is "xn--caf-dma.com".

The "xn--" is a constant. It is the same regardless of the domain. For example, the punycode URL representation of "mañana.com" is "xn--maana-pta.com".

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Integer;
sb: TChilkatStringBuilder;

begin
sb := TChilkatStringBuilder.Create(Self);

// Load the string "café" from a utf-8 text file.
success := sb.LoadFile('qa_data/txt/cafe.txt','utf-8');

sb.PunyEncode();
Memo1.Lines.Add(sb.GetAsString());

sb.PunyDecode();
Memo1.Lines.Add(sb.GetAsString());

// The output is:
// 
// caf-dma
// café
end;