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This is libidn2.info, produced by makeinfo version 6.7 from libidn2.texi. This manual is for Libidn2 (version 2.3.4, 11 July 2022), an implementation of IDNA2008/TR46 internationalized domain names. Copyright © 2011–2022 Simon Josefsson INFO-DIR-SECTION Software libraries START-INFO-DIR-ENTRY * libidn2: (libidn2). Internationalized domain names (IDNA2008/TR46) processing. END-INFO-DIR-ENTRY INFO-DIR-SECTION Localization START-INFO-DIR-ENTRY * idn2: (libidn2)Invoking idn2. Internationalized Domain Name (IDNA2008/TR46) conversion. END-INFO-DIR-ENTRY File: libidn2.info, Node: Top, Next: Introduction, Up: (dir) Libidn2 ******* This manual is for Libidn2 (version 2.3.4, 11 July 2022), an implementation of IDNA2008/TR46 internationalized domain names. Copyright © 2011–2022 Simon Josefsson * Menu: * Introduction:: What is Libidn2? * Library Functions:: Library functions. * Converting from libidn:: Demonstrate how to convert from libidn. * Examples:: Demonstrate how to use the library. * Invoking idn2:: Command line interface to the library. * Interface Index:: * Concept Index:: File: libidn2.info, Node: Introduction, Next: Library Functions, Prev: Top, Up: Top 1 Introduction ************** Libidn2 is a free software implementation of IDNA2008, Punycode and Unicode TR46. Its purpose is to encode and decode internationalized domain names. The library is a rewrite of the popular but legacy libidn library, and is backwards (API) compatible with it. See *note Converting from libidn:: for more information. For technical reference, see: • IDNA2008 Framework (<https://tools.ietf.org/html/rfc5890>) • IDNA2008 Protocol (<https://tools.ietf.org/html/rfc5891>) • IDNA2008 Unicode tables (<https://tools.ietf.org/html/rfc5892>) • IDNA2008 Bidi rule (<https://tools.ietf.org/html/rfc5893>) • Punycode (<https://tools.ietf.org/html/rfc3492>) • Unicode IDNA Compatibility Processing (<http://www.unicode.org/reports/tr46/>) Libidn2 uses GNU libunistring (<https://www.gnu.org/software/libunistring/>) for Unicode processing and optionally GNU libiconv (<https://www.gnu.org/software/libiconv/>) for character set conversion. The library is dual-licensed under LGPLv3 or GPLv2, see the file COPYING for detailed information. File: libidn2.info, Node: Library Functions, Next: Converting from libidn, Prev: Introduction, Up: Top 2 Library Functions ******************* Below are the interfaces of the Libidn2 library documented. 2.1 Header file ‘idn2.h’ ======================== To use the functions documented in this chapter, you need to include the file ‘idn2.h’ like this: #include <idn2.h> 2.2 Core Functions ================== When you have the data encoded in UTF-8 form the direct interfaces to the library are as follows. idn2_to_ascii_8z ---------------- -- Function: int idn2_to_ascii_8z (const char * INPUT, char ** OUTPUT, int FLAGS) INPUT: zero terminated input UTF-8 string. OUTPUT: pointer to newly allocated output string. FLAGS: optional ‘idn2_flags’ to modify behaviour. Convert UTF-8 domain name to ASCII string using the IDNA2008 rules. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller. The default behavior of this function (when flags are zero) is to apply the IDNA2008 rules without the TR46 amendments. As the TR46 non-transitional processing is nowadays ubiquitous, when unsure, it is recommended to call this function with the ‘IDN2_NONTRANSITIONAL’ and the ‘IDN2_NFC_INPUT’ flags for compatibility with other software. Return value: Returns ‘IDN2_OK’ on success, or error code. *Since:* 2.0.0 idn2_to_unicode_8z8z -------------------- -- Function: int idn2_to_unicode_8z8z (const char * INPUT, char ** OUTPUT, int FLAGS) INPUT: Input zero-terminated UTF-8 string. OUTPUT: Newly allocated UTF-8 output string. FLAGS: Currently unused. Converts a possibly ACE encoded domain name in UTF-8 format into a UTF-8 string (punycode decoding). The output buffer will be zero-terminated and must be deallocated by the caller. ‘output’ may be NULL to test lookup of ‘input’ without allocating memory. *Since:* 2.0.0 idn2_lookup_u8 -------------- -- Function: int idn2_lookup_u8 (const uint8_t * SRC, uint8_t ** LOOKUPNAME, int FLAGS) SRC: input zero-terminated UTF-8 string in Unicode NFC normalized form. LOOKUPNAME: newly allocated output variable with name to lookup in DNS. FLAGS: optional ‘idn2_flags’ to modify behaviour. Perform IDNA2008 lookup string conversion on domain name ‘src’ , as described in section 5 of RFC 5891. Note that the input string must be encoded in UTF-8 and be in Unicode NFC form. Pass ‘IDN2_NFC_INPUT’ in ‘flags’ to convert input to NFC form before further processing. ‘IDN2_TRANSITIONAL’ and ‘IDN2_NONTRANSITIONAL’ do already imply ‘IDN2_NFC_INPUT’ . Pass ‘IDN2_ALABEL_ROUNDTRIP’ in ‘flags’ to convert any input A-labels to U-labels and perform additional testing. This is default since version 2.2. To switch this behavior off, pass IDN2_NO_ALABEL_ROUNDTRIP Pass ‘IDN2_TRANSITIONAL’ to enable Unicode TR46 transitional processing, and ‘IDN2_NONTRANSITIONAL’ to enable Unicode TR46 non-transitional processing. Multiple flags may be specified by binary or:ing them together. After version 2.0.3: ‘IDN2_USE_STD3_ASCII_RULES’ disabled by default. Previously we were eliminating non-STD3 characters from domain strings such as _443._tcp.example.com, or IPs 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. After version 0.11: ‘lookupname’ may be NULL to test lookup of ‘src’ without allocating memory. *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, or another error code is returned. *Since:* 0.1 idn2_register_u8 ---------------- -- Function: int idn2_register_u8 (const uint8_t * ULABEL, const uint8_t * ALABEL, uint8_t ** INSERTNAME, int FLAGS) ULABEL: input zero-terminated UTF-8 and Unicode NFC string, or NULL. ALABEL: input zero-terminated ACE encoded string (xn–), or NULL. INSERTNAME: newly allocated output variable with name to register in DNS. FLAGS: optional ‘idn2_flags’ to modify behaviour. Perform IDNA2008 register string conversion on domain label ‘ulabel’ and ‘alabel’ , as described in section 4 of RFC 5891. Note that the input ‘ulabel’ must be encoded in UTF-8 and be in Unicode NFC form. Pass ‘IDN2_NFC_INPUT’ in ‘flags’ to convert input ‘ulabel’ to NFC form before further processing. It is recommended to supply both ‘ulabel’ and ‘alabel’ for better error checking, but supplying just one of them will work. Passing in only ‘alabel’ is better than only ‘ulabel’ . See RFC 5891 section 4 for more information. After version 0.11: ‘insertname’ may be NULL to test conversion of ‘src’ without allocating memory. *Returns:* On successful conversion ‘IDN2_OK’ is returned, when the given ‘ulabel’ and ‘alabel’ does not match each other ‘IDN2_UALABEL_MISMATCH’ is returned, when either of the input labels are too long ‘IDN2_TOO_BIG_LABEL’ is returned, when ‘alabel’ does does not appear to be a proper A-label ‘IDN2_INVALID_ALABEL’ is returned, or another error code is returned. 2.3 Locale Functions ==================== As a convenience, the following functions are provided that will convert the input from the locale encoding format to UTF-8 and normalize the string using NFC, and then apply the core functions described earlier. idn2_to_ascii_lz ---------------- -- Function: int idn2_to_ascii_lz (const char * INPUT, char ** OUTPUT, int FLAGS) INPUT: zero terminated input UTF-8 string. OUTPUT: pointer to newly allocated output string. FLAGS: optional ‘idn2_flags’ to modify behaviour. Convert a domain name in locale’s encoding to ASCII string using the IDNA2008 rules. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller. The default behavior of this function (when flags are zero) is to apply the IDNA2008 rules without the TR46 amendments. As the TR46 non-transitional processing is nowadays ubiquitous, when unsure, it is recommended to call this function with the ‘IDN2_NONTRANSITIONAL’ and the ‘IDN2_NFC_INPUT’ flags for compatibility with other software. *Returns:* ‘IDN2_OK’ on success, or error code. Same as described in ‘idn2_lookup_ul()’ documentation. *Since:* 2.0.0 idn2_to_unicode_8zlz -------------------- -- Function: int idn2_to_unicode_8zlz (const char * INPUT, char ** OUTPUT, int FLAGS) INPUT: Input zero-terminated UTF-8 string. OUTPUT: Newly allocated output string in current locale’s character set. FLAGS: Currently unused. Converts a possibly ACE encoded domain name in UTF-8 format into a string encoded in the current locale’s character set (punycode decoding). The output buffer will be zero-terminated and must be deallocated by the caller. ‘output’ may be NULL to test lookup of ‘input’ without allocating memory. *Since:* 2.0.0 idn2_to_unicode_lzlz -------------------- -- Function: int idn2_to_unicode_lzlz (const char * INPUT, char ** OUTPUT, int FLAGS) INPUT: Input zero-terminated string encoded in the current locale’s character set. OUTPUT: Newly allocated output string in current locale’s character set. FLAGS: Currently unused. Converts a possibly ACE encoded domain name in the locale’s character set into a string encoded in the current locale’s character set (punycode decoding). The output buffer will be zero-terminated and must be deallocated by the caller. ‘output’ may be NULL to test lookup of ‘input’ without allocating memory. *Since:* 2.0.0 idn2_lookup_ul -------------- -- Function: int idn2_lookup_ul (const char * SRC, char ** LOOKUPNAME, int FLAGS) SRC: input zero-terminated locale encoded string. LOOKUPNAME: newly allocated output variable with name to lookup in DNS. FLAGS: optional ‘idn2_flags’ to modify behaviour. Perform IDNA2008 lookup string conversion on domain name ‘src’ , as described in section 5 of RFC 5891. Note that the input is assumed to be encoded in the locale’s default coding system, and will be transcoded to UTF-8 and NFC normalized by this function. Pass ‘IDN2_ALABEL_ROUNDTRIP’ in ‘flags’ to convert any input A-labels to U-labels and perform additional testing. This is default since version 2.2. To switch this behavior off, pass IDN2_NO_ALABEL_ROUNDTRIP Pass ‘IDN2_TRANSITIONAL’ to enable Unicode TR46 transitional processing, and ‘IDN2_NONTRANSITIONAL’ to enable Unicode TR46 non-transitional processing. Multiple flags may be specified by binary or:ing them together, for example ‘IDN2_ALABEL_ROUNDTRIP’ | ‘IDN2_NONTRANSITIONAL’ . The ‘IDN2_NFC_INPUT’ in ‘flags’ is always enabled in this function. After version 0.11: ‘lookupname’ may be NULL to test lookup of ‘src’ without allocating memory. *Returns:* On successful conversion ‘IDN2_OK’ is returned, if conversion from locale to UTF-8 fails then ‘IDN2_ICONV_FAIL’ 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, or another error code is returned. *Since:* 0.1 idn2_register_ul ---------------- -- Function: int idn2_register_ul (const char * ULABEL, const char * ALABEL, char ** INSERTNAME, int FLAGS) ULABEL: input zero-terminated locale encoded string, or NULL. ALABEL: input zero-terminated ACE encoded string (xn–), or NULL. INSERTNAME: newly allocated output variable with name to register in DNS. FLAGS: optional ‘idn2_flags’ to modify behaviour. Perform IDNA2008 register string conversion on domain label ‘ulabel’ and ‘alabel’ , as described in section 4 of RFC 5891. Note that the input ‘ulabel’ is assumed to be encoded in the locale’s default coding system, and will be transcoded to UTF-8 and NFC normalized by this function. It is recommended to supply both ‘ulabel’ and ‘alabel’ for better error checking, but supplying just one of them will work. Passing in only ‘alabel’ is better than only ‘ulabel’ . See RFC 5891 section 4 for more information. After version 0.11: ‘insertname’ may be NULL to test conversion of ‘src’ without allocating memory. *Returns:* On successful conversion ‘IDN2_OK’ is returned, when the given ‘ulabel’ and ‘alabel’ does not match each other ‘IDN2_UALABEL_MISMATCH’ is returned, when either of the input labels are too long ‘IDN2_TOO_BIG_LABEL’ is returned, when ‘alabel’ does does not appear to be a proper A-label ‘IDN2_INVALID_ALABEL’ is returned, when ‘ulabel’ locale to UTF-8 conversion failed ‘IDN2_ICONV_FAIL’ is returned, or another error code is returned. 2.4 Control Flags ================= The ‘flags’ parameter can take on the following values, or a bit-wise inclusive or of any subset of the parameters: -- Global flag: idn2_flags IDN2_NFC_INPUT Apply NFC normalization on input. -- Global flag: idn2_flags IDN2_ALABEL_ROUNDTRIP Apply additional round-trip conversion of A-label inputs. -- Global flag: idn2_flags IDN2_TRANSITIONAL Perform Unicode TR46 transitional processing. -- Global flag: idn2_flags IDN2_NONTRANSITIONAL Perform Unicode TR46 non-transitional processing (default). -- Global flag: idn2_flags IDN2_NO_TR46 Disable any TR#46 transitional or non-transitional processing. -- Global flag: idn2_flags IDN2_USE_STD3_ASCII_RULES Use STD3 ASCII rules. This is a TR#46 flag and is a no-op when IDN2_NO_TR46 is specified. 2.5 Error Handling ================== idn2_strerror ------------- -- Function: const char * idn2_strerror (int RC) RC: return code from another libidn2 function. Convert internal libidn2 error code to a humanly readable string. The returned pointer must not be de-allocated by the caller. Return value: A humanly readable string describing error. idn2_strerror_name ------------------ -- Function: const char * idn2_strerror_name (int RC) RC: return code from another libidn2 function. Convert internal libidn2 error code to a string corresponding to internal header file symbols. For example, idn2_strerror_name(IDN2_MALLOC) will return the string "IDN2_MALLOC". The caller must not attempt to de-allocate the returned string. Return value: A string corresponding to error code symbol. 2.6 Return Codes ================ The functions normally return 0 on success or a negative error code. -- Return code: idn2_rc IDN2_OK Successful return. -- Return code: idn2_rc IDN2_MALLOC Memory allocation error. -- Return code: idn2_rc IDN2_NO_CODESET Could not determine locale string encoding format. -- Return code: idn2_rc IDN2_ICONV_FAIL Could not transcode locale string to UTF-8. -- Return code: idn2_rc IDN2_ENCODING_ERROR Unicode data encoding error. -- Return code: idn2_rc IDN2_NFC Error normalizing string. -- Return code: idn2_rc IDN2_PUNYCODE_BAD_INPUT Punycode invalid input. -- Return code: idn2_rc IDN2_PUNYCODE_BIG_OUTPUT Punycode output buffer too small. -- Return code: idn2_rc IDN2_PUNYCODE_OVERFLOW Punycode conversion would overflow. -- Return code: idn2_rc IDN2_TOO_BIG_DOMAIN Domain name longer than 255 characters. -- Return code: idn2_rc IDN2_TOO_BIG_LABEL Domain label longer than 63 characters. -- Return code: idn2_rc IDN2_INVALID_ALABEL Input A-label is not valid. -- Return code: idn2_rc IDN2_UALABEL_MISMATCH Input A-label and U-label does not match. -- Return code: idn2_rc IDN2_INVALID_FLAGS Invalid combination of flags. -- Return code: idn2_rc IDN2_NOT_NFC String is not NFC. -- Return code: idn2_rc IDN2_2HYPHEN String has forbidden two hyphens. -- Return code: idn2_rc IDN2_HYPHEN_STARTEND String has forbidden starting/ending hyphen. -- Return code: idn2_rc IDN2_LEADING_COMBINING String has forbidden leading combining character. -- Return code: idn2_rc IDN2_DISALLOWED String has disallowed character. -- Return code: idn2_rc IDN2_CONTEXTJ String has forbidden context-j character. -- Return code: idn2_rc IDN2_CONTEXTJ_NO_RULE String has context-j character with no rull. -- Return code: idn2_rc IDN2_CONTEXTO String has forbidden context-o character. -- Return code: idn2_rc IDN2_CONTEXTO_NO_RULE String has context-o character with no rull. -- Return code: idn2_rc IDN2_UNASSIGNED String has forbidden unassigned character. -- Return code: idn2_rc IDN2_BIDI String has forbidden bi-directional properties. -- Return code: idn2_rc IDN2_DOT_IN_LABEL Label has forbidden dot (TR46). -- Return code: idn2_rc IDN2_INVALID_TRANSITIONAL Label has character forbidden in transitional mode (TR46). -- Return code: idn2_rc IDN2_INVALID_NONTRANSITIONAL Label has character forbidden in non-transitional mode (TR46). 2.7 Memory Handling =================== idn2_free --------- -- Function: void idn2_free (void * PTR) PTR: pointer to deallocate Call free(3) on the given pointer. This function is typically only useful on systems where the library malloc heap is different from the library caller malloc heap, which happens on Windows when the library is a separate DLL. 2.8 Version Check ================= It is often desirable to check that the version of Libidn2 used is indeed one which fits all requirements. Even with binary compatibility new features may have been introduced but due to problem with the dynamic linker an old version is actually used. So you may want to check that the version is okay right after program startup. idn2_check_version ------------------ -- Function: const char * idn2_check_version (const char * REQ_VERSION) REQ_VERSION: version string to compare with, or NULL. Check IDN2 library version. This function can also be used to read out the version of the library code used. See ‘IDN2_VERSION’ for a suitable ‘req_version’ string, it corresponds to the idn2.h header file version. Normally these two version numbers match, but if you are using an application built against an older libidn2 with a newer libidn2 shared library they will be different. Return value: Check that the version of the library is at minimum the one given as a string in ‘req_version’ and return the actual version string of the library; return NULL if the condition is not met. If NULL is passed to this function no check is done and only the version string is returned. The normal way to use the function is to put something similar to the following first in your ‘main’: if (!idn2_check_version (IDN2_VERSION)) { printf ("idn2_check_version() failed:\n" "Header file incompatible with shared library.\n"); exit(EXIT_FAILURE); } File: libidn2.info, Node: Converting from libidn, Next: Examples, Prev: Library Functions, Up: Top 3 Converting from libidn ************************ This library is backwards (API) compatible with the libidn library (<https://www.gnu.org/software/libidn/>). Although it is recommended for new software to use the native libidn2 functions (i.e., the ones prefixed with ‘idn2’), old software isn’t always feasible to modify. 3.1 Converting with minimal modifications ========================================= As such, libidn2, provides compatibility macros which switch all libidn functions, to libidn2 functions in a backwards compatible way. To take advantage of these compatibility functions, it is sufficient to replace the ‘idna.h’ header in legacy code, with ‘idn2.h’. That would transform the software from using libidn, i.e., IDNA2003, to using libidn2 with IDNA2008 non-transitional encoding. 3.2 Converting to native APIs ============================= However, it is recommended to switch applications to the IDN2 native APIs. The following table provides a mapping of libidn code snippets to libidn2, for switching to IDNA2008. libidn libidn2 ------------------------------------------------------------ rc = idna_to_ascii_8z (buf, &p, IDNA_USE_STD3_ASCII_RULES);rc = idn2_to_ascii_8z (buf, &p, IDN2_USE_STD3_ASCII_RULES); if (rc != IDNA_SUCCESS) if (rc != IDN2_OK) rc = idna_to_ascii_8z (buf, &p, 0 /* any other flags */);/* we recommend to use the default flags (0), so that if (rc != IDNA_SUCCESS) * the default behavior of libidn2 applies. */ rc = idn2_to_ascii_8z (buf, &p, 0); if (rc != IDN2_OK) rc = idna_to_unicode_8z8z (buf, &p, 0 /* any flags */);rc = idn2_to_unicode_8z8z (buf, &p, 0); if (rc != IDNA_SUCCESS) if (rc != IDN2_OK) Note that, although the table only lists the UTF-8 functions, the mapping is identical for every other one on the family of toUnicode and toAscii. As the IDNA2003 details differ signicantly to IDNA2008, not all flags used in the libidn functions map to any specific flags; it is typically safe to use the suggested libidn2 flags. Exceptionally the libidn flag ‘IDNA_USE_STD3_ASCII_RULES’ is mapped to ‘IDN2_USE_STD3_ASCII_RULES’. 3.3 Converting with backwards compatibility =========================================== In several cases where IDNA2008 mappings do not exist whereas IDNA2003 mappings do, software like browsers take a backwards compatible approach. That is convert the domain to IDNA2008 form, and if that fails try the IDNA2003 conversion. The following example demonstrates that approach. rc = idn2_to_ascii_8z (buf, &p, IDN2_NONTRANSITIONAL); /* IDNA2008 */ if (rc == IDN2_DISALLOWED) rc = idn2_to_ascii_8z (buf, &p, IDN2_TRANSITIONAL); /* IDNA2003 - compatible */ 3.4 Using libidn and libidn2 code ================================= In the special case of software that needs to support both libraries (e.g., both IDNA2003 and IDNA2008), you must define ‘IDN2_SKIP_LIBIDN_COMPAT’ prior to including ‘idn2.h’ in order to disable compatibility code which overlaps with libidn functionality. That would allow software to use both libraries’ functions. 3.5 Stringprep and libidn2 ========================== The original libidn library includes functionality for the stringprep processing in ‘stringprep.h’. That functionality was an integral part of an IDNA2003 implementation, but it does not apply to IDNA2008. Furthermore, stringprep processing has been replaced by the PRECIS framework (RFC8264). For the reasons above, libidn2 does not implement stringprep or any other string processing protocols unrelated to IDNA2008. Applications requiring the stringprep processing should continue using the original libidn, and new applications should consider using the PRECIS framework. File: libidn2.info, Node: Examples, Next: Invoking idn2, Prev: Converting from libidn, Up: Top 4 Examples ********** This chapter contains example code which illustrate how Libidn2 is used when you write your own application. * Menu: * ToASCII:: Example using IDNA ToASCII. * ToUnicode:: Example using IDNA ToUnicode. * Lookup:: Example IDNA2008 Lookup domain name operation. * Register:: Example IDNA2008 Register label operation. File: libidn2.info, Node: ToASCII, Next: ToUnicode, Up: Examples 4.1 ToASCII example =================== This example demonstrates how the library is used to convert internationalized domain names into ASCII compatible names (ACE). It expects input to be in UTF-8 form. /* example-toascii.c --- Example ToASCII() code showing how to use Libidn2. * * This code is placed under public domain. */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <idn2.h> /* idn2_to_ascii_8z() */ /* * Compiling using pkg-config is recommended: * * $ cc -o example-toascii example-toascii.c $(pkg-config --cflags --libs libidn2) * $ ./example-toascii * Input domain encoded as `UTF-8': βόλος.com * Read string (length 15): ce b2 cf 8c ce bb ce bf cf 82 2e 63 6f 6d 0a * ACE label (length 17): 'xn--nxasmm1c.com' * */ int main (void) { char buf[BUFSIZ]; char *p; int rc; size_t i; if (!fgets (buf, BUFSIZ, stdin)) perror ("fgets"); buf[strlen (buf) - 1] = '\0'; printf ("Read string (length %ld): ", (long int) strlen (buf)); for (i = 0; i < strlen (buf); i++) printf ("%02x ", (unsigned) buf[i] & 0xFF); printf ("\n"); /* Use non-transitional IDNA2008 */ rc = idn2_to_ascii_8z (buf, &p, IDN2_NONTRANSITIONAL); if (rc != IDNA_SUCCESS) { printf ("ToASCII() failed (%d): %s\n", rc, idn2_strerror (rc)); return EXIT_FAILURE; } printf ("ACE label (length %ld): '%s'\n", (long int) strlen (p), p); free (p); /* or idn2_free() */ return 0; } File: libidn2.info, Node: ToUnicode, Next: Lookup, Prev: ToASCII, Up: Examples 4.2 ToUnicode example ===================== This example demonstrates how the library is used to convert ASCII compatible names (ACE) to internationalized domain names. Both input and output are in UTF-8 form. /* example-tounicode.c --- Example ToUnicode() code showing how to use Libidn2. * * This code is placed under public domain. */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <idn2.h> /* idn2_to_unicode_8z8z() */ /* * Compiling using pkg-config is recommended: * * $ cc -o example-to-unicode example-to-unicode.c $(pkg-config --cflags --libs libidn2) * $ ./example-tounicode * Input domain (ACE) encoded as `UTF-8': xn--nxasmm1c.com * * Read string (length 16): 78 6e 2d 2d 6e 78 61 73 6d 6d 31 63 2e 63 6f 6d * ACE label (length 14): 'βόλος.com' * */ int main (void) { char buf[BUFSIZ]; char *p; int rc; size_t i; if (!fgets (buf, BUFSIZ, stdin)) perror ("fgets"); buf[strlen (buf) - 1] = '\0'; printf ("Read string (length %ld): ", (long int) strlen (buf)); for (i = 0; i < strlen (buf); i++) printf ("%02x ", (unsigned) buf[i] & 0xFF); printf ("\n"); rc = idn2_to_unicode_8z8z (buf, &p, 0); if (rc != IDNA_SUCCESS) { printf ("ToUnicode() failed (%d): %s\n", rc, idn2_strerror (rc)); return EXIT_FAILURE; } printf ("ACE label (length %ld): '%s'\n", (long int) strlen (p), p); free (p); /* or idn2_free() */ return 0; } File: libidn2.info, Node: Lookup, Next: Register, Prev: ToUnicode, Up: Examples 4.3 Lookup ========== This example demonstrates how a domain name is processed before it is lookup in the DNS. The input expected is in the locale encoding. #include <stdio.h> /* printf, fflush, fgets, stdin, perror, fprintf */ #include <string.h> /* strlen */ #include <locale.h> /* setlocale */ #include <stdlib.h> /* free */ #include <idn2.h> /* idn2_lookup_ul, IDN2_OK, idn2_strerror, idn2_strerror_name */ int main (int argc, char *argv[]) { int rc; char src[BUFSIZ]; char *lookupname; setlocale (LC_ALL, ""); printf ("Enter (possibly non-ASCII) domain name to lookup: "); fflush (stdout); if (!fgets (src, sizeof (src), stdin)) { perror ("fgets"); return 1; } src[strlen (src) - 1] = '\0'; rc = idn2_lookup_ul (src, &lookupname, 0); if (rc != IDN2_OK) { fprintf (stderr, "error: %s (%s, %d)\n", idn2_strerror (rc), idn2_strerror_name (rc), rc); return 1; } printf ("IDNA2008 domain name to lookup in DNS: %s\n", lookupname); free (lookupname); return 0; } File: libidn2.info, Node: Register, Prev: Lookup, Up: Examples 4.4 Register ============ This example demonstrates how a domain label is processed before it is registered in the DNS. The input expected is in the locale encoding. #include <stdio.h> /* printf, fflush, fgets, stdin, perror, fprintf */ #include <string.h> /* strlen */ #include <locale.h> /* setlocale */ #include <stdlib.h> /* free */ #include <idn2.h> /* idn2_register_ul, IDN2_OK, idn2_strerror, idn2_strerror_name */ int main (int argc, char *argv[]) { int rc; char src[BUFSIZ]; char *insertname; setlocale (LC_ALL, ""); printf ("Enter (possibly non-ASCII) label to register: "); fflush (stdout); if (!fgets (src, sizeof (src), stdin)) { perror ("fgets"); return 1; } src[strlen (src) - 1] = '\0'; rc = idn2_register_ul (src, NULL, &insertname, 0); if (rc != IDN2_OK) { fprintf (stderr, "error: %s (%s, %d)\n", idn2_strerror (rc), idn2_strerror_name (rc), rc); return 1; } printf ("IDNA2008 label to register in DNS: %s\n", insertname); free (insertname); return 0; } File: libidn2.info, Node: Invoking idn2, Next: Interface Index, Prev: Examples, Up: Top 5 Invoking idn2 *************** ‘idn2’ translates internationalized domain names to the IDNA2008 encoded format, either for lookup or registration. If strings are specified on the command line, they are used as input and the computed output is printed to standard output ‘stdout’. If no strings are specified on the command line, the program read data, line by line, from the standard input ‘stdin’, and print the computed output to standard output. What processing is performed (e.g., lookup or register) is indicated by options. If any errors are encountered, the execution of the applications is aborted. All strings are expected to be encoded in the preferred charset used by your locale. Use ‘--debug’ to find out what this charset is. On POSIX systems you may use the ‘LANG’ environment variable to specify a different locale. To process a string that starts with ‘-’, for example ‘-foo’, use ‘--’ to signal the end of parameters, as in ‘idn2 -r -- -foo’. 5.1 Options =========== ‘idn2’ recognizes these commands: -h, --help Print help and exit -V, --version Print version and exit -d, --decode Decode (punycode) domain name -l, --lookup Lookup domain name (default) -r, --register Register label -T, --tr46t Enable TR46 transitional processing -N, --tr46nt Enable TR46 non-transitional processing --no-tr46 Disable TR46 processing --usestd3asciirules Enable STD3 ASCII rules --no-alabelroundtrip Disable A-label roundtrip for lookups --debug Print debugging information --quiet Silent operation 5.2 Environment Variables ========================= On POSIX systems the LANG environment variable can be used to override the system locale for the command being invoked. The system locale may influence what character set is used to decode data (i.e., strings on the command line or data read from the standard input stream), and to encode data to the standard output. If your system is set up correctly, however, the application will use the correct locale and character set automatically. Example usage: $ LANG=en_US.UTF-8 idn2 ... 5.3 Examples ============ Standard usage, reading input from standard input and disabling license and usage instructions: jas@latte:~$ idn2 --quiet räksmörgås.se xn--rksmrgs-5wao1o.se ... Reading input from the command line: jas@latte:~$ idn2 räksmörgås.se blåbærgrød.no xn--rksmrgs-5wao1o.se xn--blbrgrd-fxak7p.no jas@latte:~$ Testing the IDNA2008 Register function: jas@latte:~$ idn2 --register fußball xn--fuball-cta jas@latte:~$ 5.4 Troubleshooting =================== Getting character data encoded right, and making sure Libidn2 use the same encoding, can be difficult. The reason for this is that most systems may encode character data in more than one character encoding, i.e., using ‘UTF-8’ together with ‘ISO-8859-1’ or ‘ISO-2022-JP’. This problem is likely to continue to exist until only one character encoding come out as the evolutionary winner, or (more likely, at least to some extents) forever. The first step to troubleshooting character encoding problems with Libidn2 is to use the ‘--debug’ parameter to find out which character set encoding ‘idn2’ believe your locale uses. jas@latte:~$ idn2 --debug --quiet "" Charset: UTF-8 jas@latte:~$ If it prints ‘ANSI_X3.4-1968’ (i.e., ‘US-ASCII’), this indicate you have not configured your locale properly. To configure the locale, you can, for example, use ‘LANG=sv_SE.UTF-8; export LANG’ at a ‘/bin/sh’ prompt, to set up your locale for a Swedish environment using ‘UTF-8’ as the encoding. Sometimes ‘idn2’ appear to be unable to translate from your system locale into ‘UTF-8’ (which is used internally), and you will get an error message like this: idn2: lookup: could not convert string to UTF-8 One explanation is that you didn’t install the ‘iconv’ conversion tools. You can find it as a standalone library in GNU Libiconv (<https://www.gnu.org/software/libiconv/>). On many GNU/Linux systems, this library is part of the system, but you may have to install additional packages to be able to use it. Another explanation is that the error is correct and you are feeding ‘idn2’ invalid data. This can happen inadvertently if you are not careful with the character set encoding you use. For example, if your shell run in a ‘ISO-8859-1’ environment, and you invoke ‘idn2’ with the ‘LANG’ environment variable as follows, you will feed it ‘ISO-8859-1’ characters but force it to believe they are ‘UTF-8’. Naturally this will lead to an error, unless the byte sequences happen to be valid ‘UTF-8’. Note that even if you don’t get an error, the output may be incorrect in this situation, because ‘ISO-8859-1’ and ‘UTF-8’ does not in general encode the same characters as the same byte sequences. jas@latte:~$ idn2 --quiet --debug "" Charset: ISO-8859-1 jas@latte:~$ LANG=sv_SE.UTF-8 idn2 --debug räksmörgås Charset: UTF-8 input[0] = 0x72 input[1] = 0xc3 input[2] = 0xa4 input[3] = 0xc3 input[4] = 0xa4 input[5] = 0x6b input[6] = 0x73 input[7] = 0x6d input[8] = 0xc3 input[9] = 0xb6 input[10] = 0x72 input[11] = 0x67 input[12] = 0xc3 input[13] = 0xa5 input[14] = 0x73 UCS-4 input[0] = U+0072 UCS-4 input[1] = U+00e4 UCS-4 input[2] = U+00e4 UCS-4 input[3] = U+006b UCS-4 input[4] = U+0073 UCS-4 input[5] = U+006d UCS-4 input[6] = U+00f6 UCS-4 input[7] = U+0072 UCS-4 input[8] = U+0067 UCS-4 input[9] = U+00e5 UCS-4 input[10] = U+0073 output[0] = 0x72 output[1] = 0xc3 output[2] = 0xa4 output[3] = 0xc3 output[4] = 0xa4 output[5] = 0x6b output[6] = 0x73 output[7] = 0x6d output[8] = 0xc3 output[9] = 0xb6 output[10] = 0x72 output[11] = 0x67 output[12] = 0xc3 output[13] = 0xa5 output[14] = 0x73 UCS-4 output[0] = U+0072 UCS-4 output[1] = U+00e4 UCS-4 output[2] = U+00e4 UCS-4 output[3] = U+006b UCS-4 output[4] = U+0073 UCS-4 output[5] = U+006d UCS-4 output[6] = U+00f6 UCS-4 output[7] = U+0072 UCS-4 output[8] = U+0067 UCS-4 output[9] = U+00e5 UCS-4 output[10] = U+0073 xn--rksmrgs-5waap8p jas@latte:~$ The sense moral here is to forget about ‘LANG’ (instead, configure your system locale properly) unless you know what you are doing, and if you want to use ‘LANG’, do it carefully and after verifying with ‘--debug’ that you get the desired results. File: libidn2.info, Node: Interface Index, Next: Concept Index, Prev: Invoking idn2, Up: Top Interface Index *************** [index ] * Menu: * idn2_check_version: Library Functions. (line 484) * idn2_free: Library Functions. (line 463) * idn2_lookup_u8: Library Functions. (line 71) * idn2_lookup_ul: Library Functions. (line 239) * idn2_register_u8: Library Functions. (line 121) * idn2_register_ul: Library Functions. (line 281) * idn2_strerror: Library Functions. (line 345) * idn2_strerror_name: Library Functions. (line 356) * idn2_to_ascii_8z: Library Functions. (line 25) * idn2_to_ascii_lz: Library Functions. (line 166) * idn2_to_unicode_8z8z: Library Functions. (line 51) * idn2_to_unicode_8zlz: Library Functions. (line 194) * idn2_to_unicode_lzlz: Library Functions. (line 216) File: libidn2.info, Node: Concept Index, Prev: Interface Index, Up: Top Concept Index ************* [index ] * Menu: * command line: Invoking idn2. (line 6) * Examples: Examples. (line 6) * idn2: Invoking idn2. (line 6) * invoking idn2: Invoking idn2. (line 6) * libidn: Converting from libidn. (line 6) * Library Functions: Library Functions. (line 6) Tag Table: Node: Top564 Node: Introduction1121 Node: Library Functions2324 Ref: idn2_to_ascii_8z2891 Ref: idn2_to_unicode_8z8z3862 Ref: idn2_lookup_u84434 Ref: idn2_register_u86521 Ref: idn2_to_ascii_lz8406 Ref: idn2_to_unicode_8zlz9456 Ref: idn2_to_unicode_lzlz10122 Ref: idn2_lookup_ul10839 Ref: idn2_register_ul12559 Ref: idn2_strerror15091 Ref: idn2_strerror_name15435 Ref: idn2_free18491 Ref: idn2_check_version19224 Node: Converting from libidn20444 Node: Examples24495 Node: ToASCII24942 Node: ToUnicode26472 Node: Lookup28000 Node: Register29138 Node: Invoking idn230269 Node: Interface Index37303 Node: Concept Index38407 End Tag Table Local Variables: coding: utf-8 End: