(Visual FoxPro) 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 ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL lnSuccess
LOCAL loSb

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSb = CreateObject('Chilkat.StringBuilder')

* Load the string "café" from a utf-8 text file.
lnSuccess = loSb.LoadFile("qa_data/txt/cafe.txt","utf-8")

loSb.PunyEncode()
? loSb.GetAsString()

loSb.PunyDecode()
? loSb.GetAsString()

* The output is:
* 
* caf-dma
* café

RELEASE loSb