idn2_lookup_u8(3)

💖 idn2_lookup_u8 — a.k.a. the libidn2 API function 💖

okay bestie, sit DOWN, because this one is literally the main character of IDNA2008 lookups. it's <cyan>idn2_lookup_u8</cyan> from the libidn2 manual, and yes, she ate. 🍓

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✨ SYNOPSIS ✨

#include <idn2.h>

int idn2_lookup_u8(const uint8_t * src, uint8_t ** lookupname, int
flags);

that's it, that's the whole vibe. one function, three little arguments, infinite slay. 💅

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🎀 ARGUMENTS 🎀

• const uint8_t * src — your input, bestie! it's a zero-terminated UTF-8 string, and it must be in Unicode NFC normalized form. no cap, if it's not NFC you're gonna have a bad time. 😭
• uint8_t ** lookupname — the output variable, freshly allocated by the function, holding the name you're gonna look up in DNS. so it's giving "here's your glow-up result" energy. 👑
• int flags — optional idn2_flags to modify the behaviour. this is where you customize the whole situation. 🦋

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🌈 DESCRIPTION 🌈

So what does she actually do? She performs the IDNA2008 lookup string conversion on the domain name src, exactly as described in section 5 of RFC 5891. iconic behavior, honestly. 📜✨

heads up bestie: the input string must be encoded in UTF-8 and be in Unicode NFC form. both. no exceptions. that's the vibe check.

Pass IDN2_NFC_INPUT in flags to convert the input to NFC form before further processing. and listen — IDN2_TRANSITIONAL and IDN2_NONTRANSITIONAL already imply IDN2_NFC_INPUT, so no need to double up, she's got you. 🫶

Pass IDN2_ALABEL_ROUNDTRIP in flags to convert any input A-labels to U-labels and perform additional testing. and get this — this is default since version 2.2. to switch this behavior off, you pass IDN2_NO_ALABEL_ROUNDTRIP. yes, it's the "not me flipping the default" situation. 💀

Pass IDN2_TRANSITIONAL to enable Unicode TR46 transitional processing, and IDN2_NONTRANSITIONAL to enable Unicode TR46 non-transitional processing. pick your fighter. 🥊

Multiple flags may be specified by binary or:ing them together. stack 'em like bracelets. 🌸

After version 2.0.3: IDN2_USE_STD3_ASCII_RULES is disabled by default. previously we were eliminating non-STD3 characters from domain strings such as _443._tcp.example.com, or IPs like 1.2.3.4/24 provided to libidn2 functions. that was an unexpected regression for applications switching from libidn, and thus it is no longer applied by default. 😤 Use IDN2_USE_STD3_ASCII_RULES to enable that behavior again, if that's your thing.

After version 0.11: lookupname may be NULL to test lookup of src without allocating memory. a little dry-run moment, we love to see it. 🧚

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⭐ RETURNS ⭐

On successful conversion, IDN2_OK is returned. 🎉

If the output domain or any label would have been too long, IDN2_TOO_BIG_DOMAIN or IDN2_TOO_BIG_LABEL is returned — she's too big to fit, it's giving oversized luggage at the airport. 🧳

Or, you know, another error code is returned. just read the error, bestie. 🙈

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🦋 SINCE 🦋

0.1 — she's been here since the beginning. a true OG. 👑

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💜 REPORTING BUGS 💜

Found a bug? don't gatekeep, report it to <help-libidn@gnu.org>. 📧

General guidelines for reporting bugs live at: https://www.gnu.org/gethelp/

Libidn2 home page: https://www.gnu.org/software/libidn2/

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🌸 COPYRIGHT 🌸

Copyright © 2002-2025 Simon Josefsson.

Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved. periodt. 💅

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🔥 SEE ALSO 🔥

The full documentation for libidn2 is maintained as a Texinfo manual. if the info and libidn2 programs are properly installed at your site, the command:

info libidn2

should give you access to the complete manual. iykyk. 📖✨

As an alternative, you may obtain the manual from:

https://www.gnu.org/software/libidn/libidn2/manual/

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and that's the whole page, bestie! 🫶 this was libidn2 version 2.3.8, and yeah, we're deep in the idn2_lookup_u8(3) era. go forth and normalize those strings. mwah. 💖🎀🦋