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Manual Reference Pages  -  IDN_ENCODENAME (3)


idn_encodename - encode an internationalized domain name




#include <idn/api.h>

idn_result_t idn_encodename(idn_action_t actions, const char *from, char *to, size_t tolen);


The function idn_encodename() converts a domain name from and writes the result on to, at most tolen bytes. Note that from must be terminated by NUL, and tolen includes room for a NUL character.

The argument actions specifies which steps in the entire encoding process should be performed. The following list shows action names corresponding with steps of the encoding process. The function performs the steps in that order.

1. IDN_UNICODECONV Convert a domain name from local encoding (e.g. ISO-8859-1) to UTF-8.
2. IDN_MAP Perform mappings (NFC, Lowercase conversion, etc.).
3. IDN_ASCLOWER Convert ASCII uppercase letters (A..Z) to lowercase (a..z).
4. IDN_RTCONV Convert A-labels to U-labels.
5. IDN_PROHCHECK Check prohibited code points.
6. IDN_UNASCHECK Check unassigned code points.
7. IDN_NFCCHECK Check labels are in NFC.
8. IDN_PREFCHECK Check labels containing "--" in the 3rd and 4th characters.
9. IDN_HYPHCHECK Check labels beginning/ending with "-".
10. IDN_COMBCHECK Check labels beginning with a combining mark.
11. IDN_CTXJCHECK Check CONTEXTJ code points.
12a. IDN_CTXOCHECK Check CONTEXTO code points for the registration protocol.
12b. IDN_CTXOLITECHECK Check CONTEXTO code points for the lookup protocol.
13. IDN_BIDICHECK Check requirements specified in [IDNA2008-BIDI].
14. IDN_LOCALCHECK Perform local check (optional).
15. IDN_IDNCONV Convert labels in UTF-8 to Punycode.
16. IDN_LENCHECK Check length of each label.
17. IDN_RTCHECK Perform round trip check for each label.

Between the step 2 and 3, the domain name is split into labels. The step 3 through 17 are applied to each label. After the step 17, labels are joined with a separator ‘‘.’’.

A value of bitwise-OR of some actions can be specified, like:

r = idn_encodename(IDN_UNICODECONV | IDN_MAP, from, to, tolen);

Also the following actions are provided for convenience:

IDN_ENCODE_REGIST Encode a domain name with IDNA2008 registration protocol. libidnkit performs the step 1..11, 12a, 13 and 15..17. libidnkitlite performs the step 2..11, 12a, 13 and 15..17.
IDN_ENCODE_LOOKUP Encode a domain name with IDNA2008 lookup protocol. libidnkit performs the step 1..8, 10, 11, 12b, 13 and 15..17. libidnkitlite performs the step 2..8, 10, 11, 12b, 13 and 15..17.

Upon success, idn_encodename() returns idn_success. Otherwise, it returns an error code. See idn_result_tostring(3) for the complete list of error codes.


To get an address of an internationalized domain name written in the application’s local encoding, use idn_encodename() to convert the name to the format suitable for passing to resolver functions.

idn_result_t r;
char ace_name[256];
struct hostent *hp;

... r = idn_encodename(IDN_ENCODE_LOOKUP, name, ace_name, sizeof(ace_name)); if (r != idn_success) { fprintf(stderr, "idn_encodename failed: %s\n", idn_result_tostring(r)); exit(1); }

hp = gethostbyname(ace_name); ...


idnconv(1), libidnkit(3), idn_nameinit(3), idn_result_tostring(3), idn2.conf(5)
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--> IDN_ENCODENAME (3) Sep 21, 2012

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