This manual is last updated 20 March 2004 for version 0.4.6 of GNU Libidn.
Copyright © 2002, 2003, 2004 Simon Josefsson.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with the Invariant Sections being "Commercial Support", no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
Indices
Appendices
GNU Libidn is an implementation of the Stringprep, Punycode and IDNA specifications defined by the IETF Internationalized Domain Names (IDN) working group, used for internationalized domain names. The package is available under the GNU Lesser General Public License.
The library contains a generic Stringprep implementation that does Unicode 3.2 NFKC normalization, mapping and prohibitation of characters, and bidirectional character handling. Profiles for Nameprep, iSCSI, SASL and XMPP are included. Punycode and ASCII Compatible Encoding (ACE) via IDNA are supported. A mechanism to define Top-Level Domain (TLD) specific validation tables, and to compare strings against those tables, is included. Default tables for some TLDs are also included.
The Stringprep API consists of two main functions, one for converting data from the system's native representation into UTF-8, and one function to perform the Stringprep processing. Adding a new Stringprep profile for your application within the API is straightforward. The Punycode API consists of one encoding function and one decoding function. The IDNA API consists of the ToASCII and ToUnicode functions, as well as an high-level interface for converting entire domain names to and from the ACE encoded form. The TLD API consists of one set of functions to extract the TLD name from a domain string, one set of functions to locate the proper TLD table to use based on the TLD name, and core functions to validate a string against a TLD table, and some utility wrappers to perform all the steps in one call.
The library is used by, e.g., GNU SASL and Shishi to process user names and passwords. Libidn can be built into GNU Libc to enable a new system-wide getaddrinfo flag for IDN processing.
Libidn is developed for the GNU/Linux system, but runs on over 20 Unix platforms (including Solaris, IRIX, AIX, and Tru64) and Windows. Libidn is written in C and (parts of) the API is accessible from C, C++, Emacs Lisp, Python and Java.
This manual documents the library programming interface. All functions and data types provided by the library are explained. Included are also examples, and documentation for the command line tool idn that provide a quick interface to the library. The Emacs Lisp bindings for the library is also discussed.
The reader is assumed to possess basic familiarity with internationalization concepts and network programming in C or C++.
This manual can be used in several ways. If read from the beginning to the end, it gives a good introduction into the library and how it can be used in an application. Forward references are included where necessary. Later on, the manual can be used as a reference manual to get just the information needed about any particular interface of the library. Experienced programmers might want to start looking at the examples at the end of the manual (see Examples), and then only read up those parts of the interface which are unclear.
This library might have a couple of advantages over other libraries doing a similar job.
The following illustration show the components that make up Libidn, and how your application relates to the library. In the illustration, various components are shown as boxes. You see the generic StringPrep component, the various StringPrep profiles including Nameprep, the Punycode component, the IDNA component, and the TLD component. The arrows indicate aggregation, e.g., IDNA uses Punycode and Nameprep, and in turn Nameprep uses the generic StringPrep interface. The interfaces to all components are available for applications, no component within the library is hidden from the application.
Libidn has at some point in time been tested on the following platforms.
alphaev67-unknown-linux-gnu, alphaev6-unknown-linux-gnu,
arm-unknown-linux-gnu, armv4l-unknown-linux-gnu,
hppa-unknown-linux-gnu, hppa64-unknown-linux-gnu,
i686-pc-linux-gnu, ia64-unknown-linux-gnu,
m68k-unknown-linux-gnu, mips-unknown-linux-gnu,
mipsel-unknown-linux-gnu, powerpc-unknown-linux-gnu,
s390-ibm-linux-gnu, sparc-unknown-linux-gnu,
sparc64-unknown-linux-gnu.
armv4l-unknown-linux-gnu.
alphaev67-dec-osf5.1,
alphaev68-dec-osf5.1.
alphaev6-unknown-linux-gnu,
alphaev67-unknown-linux-gnu.
ia64-unknown-linux-gnu.
x86_64-unknown-linux-gnu (AMD64
Opteron “Melody”).
alphaev6-unknown-linux-gnu,
alphaev67-unknown-linux-gnu, ia64-unknown-linux-gnu.
i686-pc-linux-gnu.
i686-pc-linux-gnu.
i686-pc-linux-gnu.
i686-pc-linux-gnu.
mips-sgi-irix6.5.
rs6000-ibm-aix4.3.2.0.
i686-pc-cygwin.
ia64-hp-hpux11.22,
hppa2.0w-hp-hpux11.11.
sparc-sun-solaris2.8.
sparc-sun-solaris2.9.
alpha-unknown-netbsd1.6,
i386-unknown-netbsdelf1.6.
alpha-unknown-openbsd3.1,
i386-unknown-openbsd3.1.
alpha-unknown-freebsd4.7,
alpha-unknown-freebsd4.8, i386-unknown-freebsd4.7,
i386-unknown-freebsd4.8.
powerpc-apple-darwin6.5.
If you use Libidn on, or port Libidn to, a new platform please report it to the author.
Commercial support is available for users of GNU Libidn. The kind of support that can be purchased may include:
If you are interested, please write to:
Simon Josefsson Datakonsult Drottningholmsv. 70 112 42 Stockholm Sweden E-mail: simon@josefsson.org
If your company provide support related to GNU Libidn and would like to be mentioned here, contact the author (see Bug Reports).
The package can be downloaded from several places, including http://josefsson.org/libidn/releases/. The latest version is stored in a file, e.g., libidn-0.4.6.tar.gz where the 0.4.6 indicate the highest version number.
The package is then extracted, configured and built like many other packages that use Autoconf. For detailed information on configuring and building it, refer to the INSTALL file that is part of the distribution archive.
Here is an example terminal session that download, configure, build and install the package. You will need a few basic tools, such as sh, make and cc.
$ wget -q http://josefsson.org/libidn/releases/libidn-0.4.6.tar.gz
$ tar xfz libidn-0.4.6.tar.gz
$ cd libidn-0.4.6/
$ ./configure
...
$ make
...
$ make install
...
After that Libidn should be properly installed and ready for use.
If you think you have found a bug in Libidn, please investigate it and report it.
Please make an effort to produce a self-contained report, with something definite that can be tested or debugged. Vague queries or piecemeal messages are difficult to act on and don't help the development effort.
If your bug report is good, we will do our best to help you to get a corrected version of the software; if the bug report is poor, we won't do anything about it (apart from asking you to send better bug reports).
If you think something in this manual is unclear, or downright incorrect, or if the language needs to be improved, please also send a note.
Send your bug report to:
If you want to submit a patch for inclusion – from solve a typo you discovered, up to adding support for a new feature – you should submit it as a bug report (see Bug Reports). There are some things that you can do to increase the chances for it to be included in the official package.
Unless your patch is very small (say, under 10 lines) we require that you assign the copyright of your work to the Free Software Foundation. This is to protect the freedom of the project. If you have not already signed papers, we will send you the necessary information when you submit your contribution.
For contributions that doesn't consist of actual programming code, the only guidelines are common sense. Use it.
For code contributions, a number of style guides will help you:
If you normally code using another coding standard, there is no problem, but you should use indent to reformat the code (see GNU Indent (indent)) before submitting your work.
To use `Libidn', you have to perform some changes to your sources and the build system. The necessary changes are small and explained in the following sections. At the end of this chapter, it is described how the library is initialized, and how the requirements of the library are verified.
A faster way to find out how to adapt your application for use with `Libidn' may be to look at the examples at the end of this manual (see Examples).
The library contains a few independent parts, and each part export the interfaces (data types and functions) in a header file. You must include the appropriate header files in all programs using the library, either directly or through some other header file, like this:
#include <stringprep.h>
The header files and the functions they define are categorized as follows:
The name space of the stringprep part of Libidn is stringprep*
for function names, Stringprep* for data types and
STRINGPREP_* for other symbols. In addition the same name
prefixes with one prepended underscore are reserved for internal use
and should never be used by an application.
The name space of the punycode part of Libidn is punycode_* for
function names, Punycode* for data types and PUNYCODE_*
for other symbols. In addition the same name prefixes with one
prepended underscore are reserved for internal use and should never be
used by an application.
The name space of the IDNA part of Libidn is idna_* for
function names, Idna* for data types and IDNA_* for
other symbols. In addition the same name prefixes with one prepended
underscore are reserved for internal use and should never be used by
an application.
The name space of the TLD part of Libidn is tld_* for function
names, Tld_* for data types and TLD_* for other symbols.
In addition the same name prefixes with one prepended underscore are
reserved for internal use and should never be used by an application.
Libidn is stateless and does not need any initialization.
It is often desirable to check that the version of `Libidn' 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.
req_version: Required version number, or NULL.
Check that the the version of the library is at minimum the requested one and return the version string; return NULL if the condition is not satisfied. If a NULL is passed to this function, no check is done, but the version string is simply returned.
See STRINGPREP_VERSION for a suitable
req_versionstring.Return value: Version string of run-time library, or NULL if the run-time library does not meet the required version number.
The normal way to use the function is to put something similar to the
following first in your main:
if (!stringprep_check_version (STRINGPREP_VERSION))
{
printf ("stringprep_check_version() failed:\n"
"Header file incompatible with shared library.\n");
exit(1);
}
If you want to compile a source file including e.g. the `idna.h' header file, you must make sure that the compiler can find it in the directory hierarchy. This is accomplished by adding the path to the directory in which the header file is located to the compilers include file search path (via the -I option).
However, the path to the include file is determined at the time the source is configured. To solve this problem, `Libidn' uses the external package pkg-config that knows the path to the include file and other configuration options. The options that need to be added to the compiler invocation at compile time are output by the --cflags option to pkg-config libidn. The following example shows how it can be used at the command line:
gcc -c foo.c `pkg-config libidn --cflags`
Adding the output of pkg-config libidn --cflags to the compilers command line will ensure that the compiler can find e.g. the idna.h header file.
A similar problem occurs when linking the program with the library. Again, the compiler has to find the library files. For this to work, the path to the library files has to be added to the library search path (via the -L option). For this, the option --libs to pkg-config libidn can be used. For convenience, this option also outputs all other options that are required to link the program with the `libidn' libarary. The example shows how to link foo.o with the `libidn' library to a program foo.
gcc -o foo foo.o `pkg-config libidn --libs`
Of course you can also combine both examples to a single command by specifying both options to pkg-config:
gcc -o foo foo.c `pkg-config libidn --cflags --libs`
If your project uses Autoconf (see GNU Autoconf (autoconf))
to check for installed libraries, you might find the following snippet
illustrative. It add a new configure parameter
--with-libidn, and check for idna.h and -lidn
(possibly below the directory specified as the optional argument to
--with-libidn), and define the CPP symbol
LIBIDN if the library is found. The default behaviour is to
search for the library and enable the functionality (that is, define
the symbol) when the library is found, but if you wish to make the
default behaviour of your package be that Libidn is not used (even if
it is installed on the system), change libidn=yes to
libidn=no on the third line.
AC_ARG_WITH(libidn, AC_HELP_STRING([--with-libidn=[DIR]],
[Support IDN (needs GNU Libidn)]),
libidn=$withval, libidn=yes)
if test "$libidn" != "no"; then
if test "$libidn" != "yes"; then
LDFLAGS="${LDFLAGS} -L$libidn/lib"
CPPFLAGS="${CPPFLAGS} -I$libidn/include"
fi
AC_CHECK_HEADER(idna.h,
AC_CHECK_LIB(idn, stringprep_check_version,
[libidn=yes LIBS="${LIBS} -lidn"], libidn=no),
libidn=no)
fi
if test "$libidn" != "no" ; then
AC_DEFINE(LIBIDN, 1, [Define to 1 if you want IDN support.])
else
AC_MSG_WARN([Libidn not found])
fi
AC_MSG_CHECKING([if Libidn should be used])
AC_MSG_RESULT($libidn)
If you require that your users have installed pkg-config (which
I cannot recommend generally), the above can be done more easily as
follows.
AC_ARG_WITH(libidn, AC_HELP_STRING([--with-libidn=[DIR]],
[Support IDN (needs GNU Libidn)]),
libidn=$withval, libidn=yes)
if test "$libidn" != "no" ; then
PKG_CHECK_MODULES(LIBIDN, libidn >= 0.0.0, [libidn=yes], [libidn=no])
if test "$libidn" != "yes" ; then
libidn=no
AC_MSG_WARN([Libidn not found])
else
libidn=yes
AC_DEFINE(LIBIDN, 1, [Define to 1 if you want Libidn.])
fi
fi
AC_MSG_CHECKING([if Libidn should be used])
AC_MSG_RESULT($libidn)
The rest of this library makes extensive use of Unicode characters. In order to interface this library with the outside world, your application may need to make various Unicode transformations.
stringprep.hTo use the functions explained in this chapter, you need to include the file stringprep.h using:
#include <stringprep.h>
c: a ISO10646 character code
outbuf: output buffer, must have at least 6 bytes of space. If NULL, the length will be computed and returned and nothing will be written to
outbuf.Converts a single character to UTF-8.
Return value: number of bytes written.
p: a pointer to Unicode character encoded as UTF-8
Converts a sequence of bytes encoded as UTF-8 to a Unicode character. If
pdoes not point to a valid UTF-8 encoded character, results are undefined.Return value: the resulting character.
str: a UCS-4 encoded string
len: the maximum length of
strto use. Iflen< 0, then the string is terminated with a 0 character.items_read: location to store number of characters read read, or NULL.
items_written: location to store number of bytes written or NULL. The value here stored does not include the trailing 0 byte.
Convert a string from a 32-bit fixed width representation as UCS-4. to UTF-8. The result will be terminated with a 0 byte.
Return value: a pointer to a newly allocated UTF-8 string. This value must be freed with
free(). If an error occurs, NULL will be returned anderrorset.
str: a UTF-8 encoded string
len: the maximum length of
strto use. Iflen< 0, then the string is nul-terminated.items_written: location to store the number of characters in the result, or NULL.
Convert a string from UTF-8 to a 32-bit fixed width representation as UCS-4, assuming valid UTF-8 input. This function does no error checking on the input.
Return value: a pointer to a newly allocated UCS-4 string. This value must be freed with
free().
str: a Unicode string.
len: length of
strarray, or -1 ifstris nul-terminated.Converts UCS4 string into UTF-8 and runs
stringprep_utf8_nfkc_normalize().Return value: a newly allocated Unicode string, that is the NFKC normalized form of
str.
str: a UTF-8 encoded string.
len: length of
str, in bytes, or -1 ifstris nul-terminated.Converts a string into canonical form, standardizing such issues as whether a character with an accent is represented as a base character and combining accent or as a single precomposed character.
The normalization mode is NFKC (ALL COMPOSE). It standardizes differences that do not affect the text content, such as the above-mentioned accent representation. It standardizes the "compatibility" characters in Unicode, such as SUPERSCRIPT THREE to the standard forms (in this case DIGIT THREE). Formatting information may be lost but for most text operations such characters should be considered the same. It returns a result with composed forms rather than a maximally decomposed form.
Return value: a newly allocated string, that is the NFKC normalized form of
str.
Find out current locale charset. The function respect the CHARSET environment variable, but typically uses nl_langinfo(CODESET) when it is supported. It fall back on "ASCII" if CHARSET isn't set and nl_langinfo isn't supported or return anything.
Note that this function return the application's locale's preferred charset (or thread's locale's preffered charset, if your system support thread-specific locales). It does not return what the system may be using. Thus, if you receive data from external sources you cannot in general use this function to guess what charset it is encoded in. Use stringprep_convert from the external representation into the charset returned by this function, to have data in the locale encoding.
Return value: Return the character set used by the current locale. It will never return NULL, but use "ASCII" as a fallback.
str: input zero-terminated string.
to_codeset: name of destination character set.
from_codeset: name of origin character set, as used by
str.Convert the string from one character set to another using the system's
iconv()function.Return value: Returns newly allocated zero-terminated string which is
strtranscoded into to_codeset.
str: input zero terminated string.
Convert string encoded in the locale's character set into UTF-8 by using
stringprep_convert().Return value: Returns newly allocated zero-terminated string which is
strtranscoded into UTF-8.
str: input zero terminated string.
Convert string encoded in UTF-8 into the locale's character set by using
stringprep_convert().Return value: Returns newly allocated zero-terminated string which is
strtranscoded into the locale's character set.
Stringprep describes a framework for preparing Unicode text strings in order to increase the likelihood that string input and string comparison work in ways that make sense for typical users throughout the world. The stringprep protocol is useful for protocol identifier values, company and personal names, internationalized domain names, and other text strings.
stringprep.hTo use the functions explained in this chapter, you need to include the file stringprep.h using:
#include <stringprep.h>
Further types and structures are defined for applications that want to specify their own stringprep profile. As these are fairly obscure, and by necessity tied to the implementation, we do not document them here. Look into the stringprep.h header file, and the profiles.c source code for the details.
All functions return a code of the Stringprep_rc
enumerated type:
Successful operation. This value is guaranteed to always be zero, the remaining ones are only guaranteed to hold non-zero values, for logical comparison purposes.
String contain unassigned Unicode code points, which is forbidden by the profile.
String contain code points prohibited by the profile.
String contain code points with conflicting bidirection category.
Leading and trailing character in string not of proper bidirectional category.
Contains prohibited code points detected by bidirectional code.
Buffer handed to function was too small. This usually indicate a problem in the calling application.
The stringprep profile was inconsistent. This usually indicate an internal error in the library.
The supplied flag conflicted with profile. This usually indicate a problem in the calling application.
The supplied profile name was not known to the library.
The Unicode NFKC operation failed. This usually indicate an internal error in the library.
The
mallocwas out of memory. This is usually a fatal error.
Disable the NFKC normalization, as well as selecting the non-NFKC case folding tables. Usually the profile specifies BIDI and NFKC settings, and applications should not override it unless in special situations.
Disable the BIDI step. Usually the profile specifies BIDI and NFKC settings, and applications should not override it unless in special situations.
Make the library return with an error if string contains unassigned characters according to profile.
ucs4: input/output array with string to prepare.
len: on input, length of input array with Unicode code points, on exit, length of output array with Unicode code points.
maxucs4len: maximum length of input/output array.
flags: stringprep profile flags, or 0.
profile: pointer to stringprep profile to use.
Prepare the input UCS-4 string according to the stringprep profile, and write back the result to the input string.
The input is not required to be zero terminated (
ucs4[len] = 0). The output will not be zero terminated unlessucs4[len] = 0. Instead, seestringprep_4zi()if your input is zero terminated or if you want the output to be.Since the stringprep operation can expand the string,
maxucs4lenindicate how large the buffer holding the string is. This function will not read or write to code points outside that size.The
flagsare one of Stringprep_profile_flags, or 0.The
profilecontain the instructions to perform. Your application can define new profiles, possibly re-using the generic stringprep tables that always will be part of the library, or use one of the currently supported profiles.Return value: Returns STRINGPREP_OK iff successful, or an error code.
ucs4: input/output array with zero terminated string to prepare.
maxucs4len: maximum length of input/output array.
flags: stringprep profile flags, or 0.
profile: pointer to stringprep profile to use.
Prepare the input zero terminated UCS-4 string according to the stringprep profile, and write back the result to the input string.
Since the stringprep operation can expand the string,
maxucs4lenindicate how large the buffer holding the string is. This function will not read or write to code points outside that size.The
flagsare one of Stringprep_profile_flags, or 0.The
profilecontain the instructions to perform. Your application can define new profiles, possibly re-using the generic stringprep tables that always will be part of the library, or use one of the currently supported profiles.Return value: Returns STRINGPREP_OK iff successful, or an error code.
in: input/ouput array with string to prepare.
maxlen: maximum length of input/output array.
flags: stringprep profile flags, or 0.
profile: pointer to stringprep profile to use.
Prepare the input zero terminated UTF-8 string according to the stringprep profile, and write back the result to the input string.
Note that you must convert strings entered in the systems locale into UTF-8 before using this function, see
stringprep_locale_to_utf8().Since the stringprep operation can expand the string,
maxlenindicate how large the buffer holding the string is. This function will not read or write to characters outside that size.The
flagsare one of Stringprep_profile_flags, or 0.The
profilecontain the instructions to perform. Your application can define new profiles, possibly re-using the generic stringprep tables that always will be part of the library, or use one of the currently supported profiles.Return value: Returns STRINGPREP_OK iff successful, or an error code.
in: input array with UTF-8 string to prepare.
out: output variable with pointer to newly allocate string.
profile: name of stringprep profile to use.
flags: stringprep profile flags, or 0.
Prepare the input zero terminated UTF-8 string according to the stringprep profile, and return the result in a newly allocated variable.
Note that you must convert strings entered in the systems locale into UTF-8 before using this function, see
stringprep_locale_to_utf8().The output
outvariable must be deallocated by the caller.The
flagsare one of Stringprep_profile_flags, or 0.The
profilespecifies the name of the stringprep profile to use. It must be one of the internally supported stringprep profiles.Return value: Returns STRINGPREP_OK iff successful, or an error code.
in: input/ouput array with string to prepare.
maxlen: maximum length of input/output array.
Prepare the input UTF-8 string according to the nameprep profile. The AllowUnassigned flag is false, use
stringprep_nameprepfor true AllowUnassigned. Returns 0 iff successful, or an error code.
in: input/ouput array with string to prepare.
maxlen: maximum length of input/output array.
Prepare the input UTF-8 string according to the draft iSCSI stringprep profile. Returns 0 iff successful, or an error code.
in: input/ouput array with string to prepare.
maxlen: maximum length of input/output array.
Prepare the input UTF-8 string according to the draft SASL ANONYMOUS profile. Returns 0 iff successful, or an error code.
in: input/ouput array with string to prepare.
maxlen: maximum length of input/output array.
Prepare the input UTF-8 string according to the draft XMPP node identifier profile. Returns 0 iff successful, or an error code.
in: input/ouput array with string to prepare.
maxlen: maximum length of input/output array.
Prepare the input UTF-8 string according to the draft XMPP resource identifier profile. Returns 0 iff successful, or an error code.
Punycode is a simple and efficient transfer encoding syntax designed for use with Internationalized Domain Names in Applications. It uniquely and reversibly transforms a Unicode string into an ASCII string. ASCII characters in the Unicode string are represented literally, and non-ASCII characters are represented by ASCII characters that are allowed in host name labels (letters, digits, and hyphens). A general algorithm called Bootstring allows a string of basic code points to uniquely represent any string of code points drawn from a larger set. Punycode is an instance of Bootstring that uses particular parameter values, appropriate for IDNA.
punycode.hTo use the functions explained in this chapter, you need to include the file punycode.h using:
#include <punycode.h>
All functions return a code of the Punycode_status enumerated
type:
Successful operation. This value is guaranteed to always be zero, the remaining ones are only guaranteed to hold non-zero values, for logical comparison purposes.
The punycode function uses a special type to denote Unicode code points. It is guaranteed to always be a 32 bit unsigned integer.
A unsigned integer that hold Unicode code points.
Note that the current implementation will fail if the
input_length exceed 4294967295 (the size of
punycode_uint). This restriction may be removed in the future.
Meanwhile applications are encouraged to not depend on this problem,
and use sizeof to initialize input_length and
output_length.
The functions provided are the following two entry points:
input_length: The number of code points in the
inputarray and the number of flags in thecase_flagsarray.input: An array of code points. They are presumed to be Unicode code points, but that is not strictly REQUIRED. The array contains code points, not code units. UTF-16 uses code units D800 through DFFF to refer to code points 10000..10FFFF. The code points D800..DFFF do not occur in any valid Unicode string. The code points that can occur in Unicode strings (0..D7FF and E000..10FFFF) are also called Unicode scalar values.
case_flags: A NULL pointer or an array of boolean values parallel to the
inputarray. Nonzero (true, flagged) suggests that the corresponding Unicode character be forced to uppercase after being decoded (if possible), and zero (false, unflagged) suggests that it be forced to lowercase (if possible). ASCII code points (0..7F) are encoded literally, except that ASCII letters are forced to uppercase or lowercase according to the corresponding case flags. Ifcase_flagsis a NULL pointer then ASCII letters are left as they are, and other code points are treated as unflagged.output_length: The caller passes in the maximum number of ASCII code points that it can receive. On successful return it will contain the number of ASCII code points actually output.
output: An array of ASCII code points. It is *not* null-terminated; it will contain zeros if and only if the
inputcontains zeros. (Of course the caller can leave room for a terminator and add one if needed.)Converts a sequence of code points (presumed to be Unicode code points) to Punycode.
Return value: The return value can be any of the punycode_status values defined above except punycode_bad_input. If not punycode_success, then
output_sizeandoutputmight contain garbage.
input_length: The number of ASCII code points in the
inputarray.input: An array of ASCII code points (0..7F).
output_length: The caller passes in the maximum number of code points that it can receive into the
outputarray (which is also the maximum number of flags that it can receive into thecase_flagsarray, ifcase_flagsis not a NULL pointer). On successful return it will contain the number of code points actually output (which is also the number of flags actually output, if case_flags is not a null pointer). The decoder will never need to output more code points than the number of ASCII code points in the input, because of the way the encoding is defined. The number of code points output cannot exceed the maximum possible value of a punycode_uint, even if the suppliedoutput_lengthis greater than that.output: An array of code points like the input argument of
punycode_encode()(see above).case_flags: A NULL pointer (if the flags are not needed by the caller) or an array of boolean values parallel to the
outputarray. Nonzero (true, flagged) suggests that the corresponding Unicode character be forced to uppercase by the caller (if possible), and zero (false, unflagged) suggests that it be forced to lowercase (if possible). ASCII code points (0..7F) are output already in the proper case, but their flags will be set appropriately so that applying the flags would be harmless.Converts Punycode to a sequence of code points (presumed to be Unicode code points).
Return value: The return value can be any of the punycode_status values defined above. If not punycode_success, then
output_length,output, andcase_flagsmight contain garbage.
Until now, there has been no standard method for domain names to use characters outside the ASCII repertoire. The IDNA document defines internationalized domain names (IDNs) and a mechanism called IDNA for handling them in a standard fashion. IDNs use characters drawn from a large repertoire (Unicode), but IDNA allows the non-ASCII characters to be represented using only the ASCII characters already allowed in so-called host names today. This backward-compatible representation is required in existing protocols like DNS, so that IDNs can be introduced with no changes to the existing infrastructure. IDNA is only meant for processing domain names, not free text.
idna.hTo use the functions explained in this chapter, you need to include the file idna.h using:
#include <idna.h>
All functions return a exit code:
Successful operation. This value is guaranteed to always be zero, the remaining ones are only guaranteed to hold non-zero values, for logical comparison purposes.
For IDNA_USE_STD3_ASCII_RULES, indicate that the string contains non-LDH ASCII characters.
For IDNA_USE_STD3_ASCII_RULES, indicate that the string contains a leading or trailing hyphen-minus (U+002D).
The final output string is not within the (inclusive) range 1 to 63 characters.
The string does not contain the ACE prefix (for ToUnicode).
The ToASCII operation on output string does not equal the input.
Could not allocate buffer (this is typically a fatal error).
Could not dlopen libcidn DSO (only used internally in libc).
The IDNA flags parameter can take on the following values, or a
bit-wise inclusive or of any subset of the parameters:
Check output to make sure it is a STD3 conforming host name.
The idea behind the IDNA function names are as follows: the
idna_to_ascii_4i and idna_to_unicode_44i functions are
the core IDNA primitives. The 4 indicate that the function
takes UCS-4 strings (i.e., Unicode code points encoded in a 32-bit
unsigned integer type) of the specified length. The i indicate
that the data is written “inline” into the buffer. This means the
caller is responsible for allocating (and deallocating) the string,
and providing the library with the allocated length of the string.
The output length is written in the output length variable. The
remaining functions all contain the z indicator, which means
the strings are zero terminated. All output strings are allocated by
the library, and must be deallocated by the caller. The 4
indicator again means that the string is UCS-4, the 8 means the
strings are UTF-8 and the l indicator means the strings are
encoded in the encoding used by the current locale.
The functions provided are the following entry points:
in: input array with unicode code points.
inlen: length of input array with unicode code points.
out: output zero terminated string that must have room for at least 63 characters plus the terminating zero.
flags: IDNA flags, e.g. IDNA_ALLOW_UNASSIGNED or IDNA_USE_STD3_ASCII_RULES.
The ToASCII operation takes a sequence of Unicode code points that make up one label and transforms it into a sequence of code points in the ASCII range (0..7F). If ToASCII succeeds, the original sequence and the resulting sequence are equivalent labels.
It is important to note that the ToASCII operation can fail. ToASCII fails if any step of it fails. If any step of the ToASCII operation fails on any label in a domain name, that domain name MUST NOT be used as an internationalized domain name. The method for deadling with this failure is application-specific.
The inputs to ToASCII are a sequence of code points, the AllowUnassigned flag, and the UseSTD3ASCIIRules flag. The output of ToASCII is either a sequence of ASCII code points or a failure condition.
ToASCII never alters a sequence of code points that are all in the ASCII range to begin with (although it could fail). Applying the ToASCII operation multiple times has exactly the same effect as applying it just once.
Return value: Returns 0 on success, or an error code.
in: input array with unicode code points.
inlen: length of input array with unicode code points.
out: output array with unicode code points.
outlen: on input, maximum size of output array with unicode code points, on exit, actual size of output array with unicode code points.
flags: IDNA flags, e.g. IDNA_ALLOW_UNASSIGNED or IDNA_USE_STD3_ASCII_RULES.
The ToUnicode operation takes a sequence of Unicode code points that make up one label and returns a sequence of Unicode code points. If the input sequence is a label in ACE form, then the result is an equivalent internationalized label that is not in ACE form, otherwise the original sequence is returned unaltered.
ToUnicode never fails. If any step fails, then the original input sequence is returned immediately in that step.
The Punycode decoder can never output more code points than it inputs, but Nameprep can, and therefore ToUnicode can. Note that the number of octets needed to represent a sequence of code points depends on the particular character encoding used.
The inputs to ToUnicode are a sequence of code points, the AllowUnassigned flag, and the UseSTD3ASCIIRules flag. The output of ToUnicode is always a sequence of Unicode code points.
Return value: Returns error condition, but it must only be used for debugging purposes. The output buffer is always guaranteed to contain the correct data according to the specification (sans malloc induced errors). NB! This means that you normally ignore the return code from this function, as checking it means breaking the standard.
input: zero terminated input Unicode string.
output: pointer to newly allocated output string.
flags: IDNA flags, e.g. IDNA_ALLOW_UNASSIGNED or IDNA_USE_STD3_ASCII_RULES.
Convert UCS-4 domain name to ASCII string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.
Return value: Returns IDNA_SUCCESS on success, or error code.
input: zero terminated input UTF-8 string.
output: pointer to newly allocated output string.
flags: IDNA flags, e.g. IDNA_ALLOW_UNASSIGNED or IDNA_USE_STD3_ASCII_RULES.
Convert UTF-8 domain name to ASCII string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.
Return value: Returns IDNA_SUCCESS on success, or error code.
input: zero terminated input string encoded in the current locale's character set.
output: pointer to newly allocated output string.
flags: IDNA flags, e.g. IDNA_ALLOW_UNASSIGNED or IDNA_USE_STD3_ASCII_RULES.
Convert domain name in the locale's encoding to ASCII string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.
Return value: Returns IDNA_SUCCESS on success, or error code.
input: zero-terminated Unicode string.
output: pointer to newly allocated output Unicode string.
flags: IDNA flags, e.g. IDNA_ALLOW_UNASSIGNED or IDNA_USE_STD3_ASCII_RULES.
Convert possibly ACE encoded domain name in UCS-4 format into a UCS-4 string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.
Return value: Returns IDNA_SUCCESS on success, or error code.
input: zero-terminated UTF-8 string.
output: pointer to newly allocated output Unicode string.
flags: IDNA flags, e.g. IDNA_ALLOW_UNASSIGNED or IDNA_USE_STD3_ASCII_RULES.
Convert possibly ACE encoded domain name in UTF-8 format into a UCS-4 string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.
Return value: Returns IDNA_SUCCESS on success, or error code.
input: zero-terminated UTF-8 string.
output: pointer to newly allocated output UTF-8 string.
flags: IDNA flags, e.g. IDNA_ALLOW_UNASSIGNED or IDNA_USE_STD3_ASCII_RULES.
Convert possibly ACE encoded domain name in UTF-8 format into a UTF-8 string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.
Return value: Returns IDNA_SUCCESS on success, or error code.
input: zero-terminated UTF-8 string.
output: pointer to newly allocated output string encoded in the current locale's character set.
flags: IDNA flags, e.g. IDNA_ALLOW_UNASSIGNED or IDNA_USE_STD3_ASCII_RULES.
Convert possibly ACE encoded domain name in UTF-8 format into a string encoded in the current locale's character set. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.
Return value: Returns IDNA_SUCCESS on success, or error code.
input: zero-terminated string encoded in the current locale's character set.
output: pointer to newly allocated output string encoded in the current locale's character set.
flags: IDNA flags, e.g. IDNA_ALLOW_UNASSIGNED or IDNA_USE_STD3_ASCII_RULES.
Convert possibly ACE encoded domain name in the locale's character set into a string encoded in the current locale's character set. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.
Return value: Returns IDNA_SUCCESS on success, or error code.
Organizations that manage some Top Level Domains (TLDs) have published tables with characters they accept within the domain. The reason may be to reduce complexity that come from using the full Unicode range, and to protect themselves from future (backwards incompatible) changes in the IDN or Unicode specifications. Libidn implement an infrastructure for defining and checking strings against such tables. Libidn also ship some tables from TLDs that we have managed to get permission to use them from. Because these tables are even less static than Unicode or StringPrep tables, it is likely that they will be updated from time to time (even in backwards incompatibe ways). The Libidn interface provide a “version” field for each TLD table, which can be compared for equality to guarantee the same operation over time.
From a design point of view, you can regard the TLD tables for IDN as the “localization” step that come after the “internationalization” step provided by the IETF standards.
The TLD functionality rely on up-to-date tables. The latest version of Libidn aim to provide these, but tables with unclear copying conditions, or generally experimental tables, are not included. Some such tables can be found at http://tldchk.berlios.de.
tld.hTo use the functions explained in this chapter, you need to include the file tld.h using:
#include <tld.h>
Most functions return a exit code:
Successful operation. This value is guaranteed to always be zero, the remaining ones are only guaranteed to hold non-zero values, for logical comparison purposes.
in: Array of unicode code points to process. Does not need to be zero terminated.
inlen: Number of unicode code points.
errpos: Position of offending character is returned here.
tld: Data structure representing the restrictions for which the input should be tested.
Test each of the code points in
infor whether or not they are allowed by the data structure intld, return the position of the first character for which this is not the case inerrpos.Return value: Returns TLD_SUCCESS if all code points are valid or when
tldis null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.
in: Zero terminated array of unicode code points to process.
errpos: Position of offending character is returned here.
tld: Data structure representing the restrictions for which the input should be tested.
Test each of the code points in
infor whether or not they are allowed by the data structure intld, return the position of the first character for which this is not the case inerrpos.Return value: Returns TLD_SUCCESS if all code points are valid or when
tldis null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.
in: Array of unicode code points to process. Does not need to be zero terminated.
inlen: Number of unicode code points.
out: Zero terminated ascii result string pointer.
Isolate the top-level domain of
inand return it as an ASCII string inout.Return value: Return TLD_SUCCESS on success, the corresponding error code otherwise.
in: Zero terminated array of unicode code points to process.
out: Zero terminated ascii result string pointer.
Isolate the top-level domain of
inand return it as an ASCII string inout.Return value: Returns TLD_SUCCESS on success, the corresponding error code otherwise.
in: Zero terminated character array to process.
out: Zero terminated ascii result string pointer.
Isolate the top-level domain of
inand return it as an ASCII string inout. The input stringinmay be UTF-8, ISO-8859-1 or any ASCII compatible character encoding.Return value: Returns TLD_SUCCESS on success, the corresponding error code otherwise.
tld: TLD name (e.g. "com") as zero terminated ASCII byte string.
tables: Zero terminated array of info-structures for TLDs.
Get the TLD table for a named TLD by searching through the given TLD table array.
Return value: Return structure corresponding to TLD
tldby going thrutables, or return NULL if no such structure is found.
tld: TLD name (e.g. "com") as zero terminated ASCII byte string.
overrides: Additional well-formed info-structures for TLDs, or NULL to only use library deault tables.
Get the TLD table for a named TLD, using the internal defaults, possibly overrided by the (optional) supplied tables.
Return value: Return structure corresponding to TLD
tld_str, first looking throughoverridesthen thru built-in list, or NULL if no such structure found.
in: Array of unicode code points to process. Does not need to be zero terminated.
inlen: Number of unicode code points.
errpos: Position of offending character is returned here.
overrides: An array of additional domain restriction structures that complement and supersede the built-in information.
Test each of the code points in
infor whether or not they are allowed by the information inoverridesor by the built-in TLD restriction data. When data for the same TLD is available both internally and inoverrides, the information inoverridestakes precedence. If several entries for a specific TLD are found, the first one is used. Ifoverridesis NULL, only the built-in information is used. The position of the first offending character is returned inerrpos.Return value: Returns TLD_SUCCESS if all code points are valid or when
tldis null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.
in: Zero-terminated array of unicode code points to process.
errpos: Position of offending character is returned here.
overrides: An array of additional domain restriction structures that complement and supersede the built-in information.
Test each of the code points in
infor whether or not they are allowed by the information inoverridesor by the built-in TLD restriction data. When data for the same TLD is available both internally and inoverrides, the information inoverridestakes precedence. If several entries for a specific TLD are found, the first one is used. Ifoverridesis NULL, only the built-in information is used. The position of the first offending character is returned inerrpos.Return value: Returns TLD_SUCCESS if all code points are valid or when
tldis null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.
in: Zero-terminated UTF8 string to process.
errpos: Position of offending character is returned here.
overrides: An array of additional domain restriction structures that complement and supersede the built-in information.
Test each of the characters in
infor whether or not they are allowed by the information inoverridesor by the built-in TLD restriction data. When data for the same TLD is available both internally and inoverrides, the information inoverridestakes precedence. If several entries for a specific TLD are found, the first one is used. Ifoverridesis NULL, only the built-in information is used. The position of the first offending character is returned inerrpos. Note that the error position refers to the decoded character offset rather than the byte position in the string.Return value: Returns TLD_SUCCESS if all characters are valid or when
tldis null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.
in: Zero-terminated string in the current locales encoding to process.
errpos: Position of offending character is returned here.
overrides: An array of additional domain restriction structures that complement and supersede the built-in information.
Test each of the characters in
infor whether or not they are allowed by the information inoverridesor by the built-in TLD restriction data. When data for the same TLD is available both internally and inoverrides, the information inoverridestakes precedence. If several entries for a specific TLD are found, the first one is used. Ifoverridesis NULL, only the built-in information is used. The position of the first offending character is returned inerrpos. Note that the error position refers to the decoded character offset rather than the byte position in the string.Return value: Returns TLD_SUCCESS if all characters are valid or when
tldis null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.
This chapter contains example code which illustrate how `Libidn' can be used when writing your own application.
This example demonstrates how the stringprep functions are used.
/* example.c Example code showing how to use stringprep().
* Copyright (C) 2002, 2003 Simon Josefsson
*
* This file is part of GNU Libidn.
*
* GNU Libidn is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* GNU Libidn is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with GNU Libidn; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stringprep.h>
/*
* Compiling using libtool and pkg-config is recommended:
*
* $ libtool cc -o example example.c `pkg-config --cflags --libs libidn`
* $ ./example
* Input string encoded as `ISO-8859-1': ª
* Before locale2utf8 (length 2): aa 0a
* Before stringprep (length 3): c2 aa 0a
* After stringprep (length 2): 61 0a
* $
*
*/
int
main (int argc, char *argv[])
{
char buf[BUFSIZ];
char *p;
int rc;
size_t i;
printf ("Input string encoded as `%s': ", stringprep_locale_charset ());
fflush (stdout);
fgets (buf, BUFSIZ, stdin);
printf ("Before locale2utf8 (length %d): ", strlen (buf));
for (i = 0; i < strlen (buf); i++)
printf ("%02x ", buf[i] & 0xFF);
printf ("\n");
p = stringprep_locale_to_utf8 (buf);
if (p)
{
strcpy (buf, p);
free (p);
}
else
printf ("Could not convert string to UTF-8, continuing anyway...\n");
printf ("Before stringprep (length %d): ", strlen (buf));
for (i = 0; i < strlen (buf); i++)
printf ("%02x ", buf[i] & 0xFF);
printf ("\n");
rc = stringprep (buf, BUFSIZ, 0, stringprep_nameprep);
if (rc != STRINGPREP_OK)
printf ("Stringprep failed with rc %d...\n", rc);
else
{
printf ("After stringprep (length %d): ", strlen (buf));
for (i = 0; i < strlen (buf); i++)
printf ("%02x ", buf[i] & 0xFF);
printf ("\n");
}
return 0;
}
This example demonstrates how the punycode functions are used.
/* example2.c Example code showing how to use punycode.
* Copyright (C) 2002, 2003 Simon Josefsson
* Copyright (C) 2002 Adam M. Costello
*
* This file is part of GNU Libidn.
*
* GNU Libidn is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* GNU Libidn is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with GNU Libidn; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
/*
* This file is derived from RFC 3492 written by Adam M. Costello.
*
* Disclaimer and license: Regarding this entire document or any
* portion of it (including the pseudocode and C code), the author
* makes no guarantees and is not responsible for any damage resulting
* from its use. The author grants irrevocable permission to anyone
* to use, modify, and distribute it in any way that does not diminish
* the rights of anyone else to use, modify, and distribute it,
* provided that redistributed derivative works do not contain
* misleading author or version information. Derivative works need
* not be licensed under similar terms.
*
*/
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <punycode.h>
/* For testing, we'll just set some compile-time limits rather than */
/* use malloc(), and set a compile-time option rather than using a */
/* command-line option. */
enum
{
unicode_max_length = 256,
ace_max_length = 256
};
static void
usage (char **argv)
{
fprintf (stderr,
"\n"
"%s -e reads code points and writes a Punycode string.\n"
"%s -d reads a Punycode string and writes code points.\n"
"\n"
"Input and output are plain text in the native character set.\n"
"Code points are in the form u+hex separated by whitespace.\n"
"Although the specification allows Punycode strings to contain\n"
"any characters from the ASCII repertoire, this test code\n"
"supports only the printable characters, and needs the Punycode\n"
"string to be followed by a newline.\n"
"The case of the u in u+hex is the force-to-uppercase flag.\n",
argv[0], argv[0]);
exit (EXIT_FAILURE);
}
static void
fail (const char *msg)
{
fputs (msg, stderr);
exit (EXIT_FAILURE);
}
static const char too_big[] =
"input or output is too large, recompile with larger limits\n";
static const char invalid_input[] = "invalid input\n";
static const char overflow[] = "arithmetic overflow\n";
static const char io_error[] = "I/O error\n";
/* The following string is used to convert printable */
/* characters between ASCII and the native charset: */
static const char print_ascii[] = "\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n" "\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n" " !\"#$%&'()*+,-./" "0123456789:;<=>?" "\0x40" /* at sign */
"ABCDEFGHIJKLMNO"
"PQRSTUVWXYZ[\\]^_" "`abcdefghijklmno" "pqrstuvwxyz{|}~\n";
int
main (int argc, char **argv)
{
enum punycode_status status;
int r;
size_t input_length, output_length, j;
unsigned char case_flags[unicode_max_length];
if (argc != 2)
usage (argv);
if (argv[1][0] != '-')
usage (argv);
if (argv[1][2] != 0)
usage (argv);
if (argv[1][1] == 'e')
{
uint32_t input[unicode_max_length];
unsigned long codept;
char output[ace_max_length + 1], uplus[3];
int c;
/* Read the input code points: */
input_length = 0;
for (;;)
{
r = scanf ("%2s%lx", uplus, &codept);
if (ferror (stdin))
fail (io_error);
if (r == EOF || r == 0)
break;
if (r != 2 || uplus[1] != '+' || codept > (uint32_t) - 1)
{
fail (invalid_input);
}
if (input_length == unicode_max_length)
fail (too_big);
if (uplus[0] == 'u')
case_flags[input_length] = 0;
else if (uplus[0] == 'U')
case_flags[input_length] = 1;
else
fail (invalid_input);
input[input_length++] = codept;
}
/* Encode: */
output_length = ace_max_length;
status = punycode_encode (input_length, input, case_flags,
&output_length, output);
if (status == punycode_bad_input)
fail (invalid_input);
if (status == punycode_big_output)
fail (too_big);
if (status == punycode_overflow)
fail (overflow);
assert (status == punycode_success);
/* Convert to native charset and output: */
for (j = 0; j < output_length; ++j)
{
c = output[j];
assert (c >= 0 && c <= 127);
if (print_ascii[c] == 0)
fail (invalid_input);
output[j] = print_ascii[c];
}
output[j] = 0;
r = puts (output);
if (r == EOF)
fail (io_error);
return EXIT_SUCCESS;
}
if (argv[1][1] == 'd')
{
char input[ace_max_length + 2], *p, *pp;
uint32_t output[unicode_max_length];
/* Read the Punycode input string and convert to ASCII: */
fgets (input, ace_max_length + 2, stdin);
if (ferror (stdin))
fail (io_error);
if (feof (stdin))
fail (invalid_input);
input_length = strlen (input) - 1;
if (input[input_length] != '\n')
fail (too_big);
input[input_length] = 0;
for (p = input; *p != 0; ++p)
{
pp = strchr (print_ascii, *p);
if (pp == 0)
fail (invalid_input);
*p = pp - print_ascii;
}
/* Decode: */
output_length = unicode_max_length;
status = punycode_decode (input_length, input, &output_length,
output, case_flags);
if (status == punycode_bad_input)
fail (invalid_input);
if (status == punycode_big_output)
fail (too_big);
if (status == punycode_overflow)
fail (overflow);
assert (status == punycode_success);
/* Output the result: */
for (j = 0; j < output_length; ++j)
{
r = printf ("%s+%04lX\n",
case_flags[j] ? "U" : "u", (unsigned long) output[j]);
if (r < 0)
fail (io_error);
}
return EXIT_SUCCESS;
}
usage (argv);
return EXIT_SUCCESS; /* not reached, but quiets compiler warning */
}
This example demonstrates how the library is used to convert internationalized domain names into ASCII compatible names.
/* example3.c Example ToASCII() code showing how to use Libidn.
* Copyright (C) 2002, 2003 Simon Josefsson
*
* This file is part of GNU Libidn.
*
* GNU Libidn is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* GNU Libidn is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with GNU Libidn; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stringprep.h> /* stringprep_locale_charset() */
#include <idna.h> /* idna_to_ascii_lz() */
/*
* Compiling using libtool and pkg-config is recommended:
*
* $ libtool cc -o example3 example3.c `pkg-config --cflags --libs libidn`
* $ ./example3
* Input domain encoded as `ISO-8859-1': www.räksmörgåsª.example
* Read string (length 23): 77 77 77 2e 72 e4 6b 73 6d f6 72 67 e5 73 aa 2e 65 78 61 6d 70 6c 65
* ACE label (length 33): 'www.xn--rksmrgsa-0zap8p.example'
* 77 77 77 2e 78 6e 2d 2d 72 6b 73 6d 72 67 73 61 2d 30 7a 61 70 38 70 2e 65 78 61 6d 70 6c 65
* $
*
*/
int
main (int argc, char *argv[])
{
char buf[BUFSIZ];
char *p;
int rc;
size_t i;
printf ("Input domain encoded as `%s': ", stringprep_locale_charset ());
fflush (stdout);
fgets (buf, BUFSIZ, stdin);
buf[strlen (buf) - 1] = '\0';
printf ("Read string (length %d): ", strlen (buf));
for (i = 0; i < strlen (buf); i++)
printf ("%02x ", buf[i] & 0xFF);
printf ("\n");
rc = idna_to_ascii_lz (buf, &p, 0);
if (rc != IDNA_SUCCESS)
{
printf ("ToASCII() failed... %d\n", rc);
exit (1);
}
printf ("ACE label (length %d): '%s'\n", strlen (p), p);
for (i = 0; i < strlen (p); i++)
printf ("%02x ", p[i] & 0xFF);
printf ("\n");
free (p);
return 0;
}
This example demonstrates how the library is used to convert ASCII compatible names to internationalized domain names.
/* example4.c Example ToUnicode() code showing how to use Libidn.
* Copyright (C) 2002, 2003 Simon Josefsson
*
* This file is part of GNU Libidn.
*
* GNU Libidn is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* GNU Libidn is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with GNU Libidn; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stringprep.h> /* stringprep_locale_charset() */
#include <idna.h> /* idna_to_unicode_lzlz() */
/*
* Compiling using libtool and pkg-config is recommended:
*
* $ libtool cc -o example4 example4.c `pkg-config --cflags --libs libidn`
* $ ./example4
* Input domain encoded as `ISO-8859-1': www.xn--rksmrgsa-0zap8p.example
* Read string (length 33): 77 77 77 2e 78 6e 2d 2d 72 6b 73 6d 72 67 73 61 2d 30 7a 61 70 38 70 2e 65 78 61 6d 70 6c 65
* ACE label (length 23): 'www.räksmörgåsa.example'
* 77 77 77 2e 72 e4 6b 73 6d f6 72 67 e5 73 61 2e 65 78 61 6d 70 6c 65
* $
*
*/
int
main (int argc, char *argv[])
{
char buf[BUFSIZ];
char *p;
int rc;
size_t i;
printf ("Input domain encoded as `%s': ", stringprep_locale_charset ());
fflush (stdout);
fgets (buf, BUFSIZ, stdin);
buf[strlen (buf) - 1] = '\0';
printf ("Read string (length %d): ", strlen (buf));
for (i = 0; i < strlen (buf); i++)
printf ("%02x ", buf[i] & 0xFF);
printf ("\n");
rc = idna_to_unicode_lzlz (buf, &p, 0);
if (rc != IDNA_SUCCESS)
{
printf ("ToUnicode() failed... %d\n", rc);
exit (1);
}
printf ("ACE label (length %d): '%s'\n", strlen (p), p);
for (i = 0; i < strlen (p); i++)
printf ("%02x ", p[i] & 0xFF);
printf ("\n");
free (p);
return 0;
}
This example demonstrates how the library is used to check a string for invalid characters within a specific TLD.
/* example5.c --- Example TLD checking.
* Copyright (C) 2004 Simon Josefsson
*
* This file is part of GNU Libidn.
*
* GNU Libidn is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* GNU Libidn is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with GNU Libidn; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* Get stringprep_locale_charset, etc. */
#include <stringprep.h>
/* Get idna_to_ascii_8z, etc. */
#include <idna.h>
/* Get tld_check_4z. */
#include <tld.h>
/*
* Compiling using libtool and pkg-config is recommended:
*
* $ libtool cc -o example5 example5.c `pkg-config --cflags --libs libidn`
* $ ./example5
* Input domain encoded as `UTF-8': fooß.no
* Read string (length 8): 66 6f 6f c3 9f 2e 6e 6f
* ToASCII string (length 8): fooss.no
* ToUnicode string: U+0066 U+006f U+006f U+0073 U+0073 U+002e U+006e U+006f
* Domain accepted by TLD check
*
* $ ./example5
* Input domain encoded as `UTF-8': gr€€n.no
* Read string (length 12): 67 72 e2 82 ac e2 82 ac 6e 2e 6e 6f
* ToASCII string (length 16): xn--grn-l50aa.no
* ToUnicode string: U+0067 U+0072 U+20ac U+20ac U+006e U+002e U+006e U+006f
* Domain rejected by TLD check, Unicode position 2
*
*/
int
main (int argc, char *argv[])
{
char buf[BUFSIZ];
char *p;
uint32_t *r;
int rc;
size_t errpos, i;
printf ("Input domain encoded as `%s': ", stringprep_locale_charset ());
fflush (stdout);
fgets (buf, BUFSIZ, stdin);
buf[strlen (buf) - 1] = '\0';
printf ("Read string (length %d): ", strlen (buf));
for (i = 0; i < strlen (buf); i++)
printf ("%02x ", buf[i] & 0xFF);
printf ("\n");
p = stringprep_locale_to_utf8 (buf);
if (p)
{
strcpy (buf, p);
free (p);
}
else
printf ("Could not convert string to UTF-8, continuing anyway...\n");
rc = idna_to_ascii_8z (buf, &p, 0);
if (rc != IDNA_SUCCESS)
{
printf ("idna_to_ascii_8z failed (%d)...\n", rc);
return 2;
}
printf ("ToASCII string (length %d): %s\n", strlen (p), p);
rc = idna_to_unicode_8z4z (p, &r, 0);
free (p);
if (rc != IDNA_SUCCESS)
{
printf ("idna_to_unicode_8z4z failed (%d)...\n", rc);
return 2;
}
printf ("ToUnicode string: ");
for (i = 0; r[i]; i++)
printf ("U+%04x ", r[i]);
printf ("\n");
rc = tld_check_4z (r, &errpos, NULL);
free (r);
if (rc == TLD_INVALID)
{
printf ("Domain rejected by TLD check, Unicode position %d\n", errpos);
return 1;
}
else if (rc != TLD_SUCCESS)
{
printf ("tld_check_4z() failed... %d\n", rc);
return 2;
}
printf ("Domain accepted by TLD check\n");
return 0;
}
GNU Libidn (idn) – Internationalized Domain Names command line tool
idn allows internationalized string preparation
(stringprep), encoding and decoding of punycode data, and IDNA
ToASCII/ToUnicode operations to be performed on the command line.
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., ToASCII, or Punycode encode) 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.
You can override the charset used by setting environment variable
CHARSET.
To process a string that starts with -, for example
-foo, use -- to signal the end of parameters, as in
idn --quiet -a -- -foo.
idn recognizes these commands:
-h, --help Print help and exit
-V, --version Print version and exit
-s, --stringprep Prepare string according to nameprep profile
-d, --punycode-decode Decode Punycode
-e, --punycode-encode Encode Punycode
-a, --idna-to-ascii Convert to ACE according to IDNA (default)
-u, --idna-to-unicode Convert from ACE according to IDNA
--allow-unassigned Toggle IDNA AllowUnassigned flag (default=off)
--usestd3asciirules Toggle IDNA UseSTD3ASCIIRules flag (default=off)
-t, --tld Check string for TLD specific rules
Only for --idna-to-ascii and --idna-to-unicode
(default=on)
-p, --profile=STRING Use specified stringprep profile instead
Valid stringprep profiles are `Nameprep',
`iSCSI', `Nodeprep', `Resourceprep', `trace', and
`SASLprep'.
--debug Print debugging information (default=off)
--quiet Silent operation (default=off)
The CHARSET environment variable can be used to override what character set to be used for decoding incoming data (i.e., on the command line or on the standard input stream), and to encode data to the standard output. If your system is set up correctly, however, the application will guess which character set is used automatically. Example usage:
$ CHARSET=ISO-8859-1 idn --punycode-encode
...
Standard usage, reading input from standard input:
jas@latte:~$ idn
libidn 0.3.5
Copyright 2002, 2003 Simon Josefsson.
GNU Libidn comes with NO WARRANTY, to the extent permitted by law.
You may redistribute copies of GNU Libidn under the terms of
the GNU Lesser General Public License. For more information
about these matters, see the file named COPYING.LIB.
Type each input string on a line by itself, terminated by a newline character.
räksmörgås.se
xn--rksmrgs-5wao1o.se
jas@latte:~$
Reading input from command line, and disabling copyright and license information:
jas@latte:~$ idn --quiet räksmörgås.se blåbærgrød.no
xn--rksmrgs-5wao1o.se
xn--blbrgrd-fxak7p.no
jas@latte:~$
Accessing a specific StringPrep profile directly:
jas@latte:~$ idn --quiet --profile=SASLprep --stringprep teßtª
teßta
jas@latte:~$
Getting character data encoded right, and making sure Libidn use the
same encoding, can be difficult. The reason for this is that most
systems 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 Libidn is to use the --debug parameter to find out which character set encoding idn believe your locale uses.
jas@latte:~$ idn --debug --quiet ""
system locale uses 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 idn appear to be unable to translate from your system
locale into UTF-8 (which is used internally), and you get an
error like the following:
jas@latte:~$ idn --quiet foo
idn: could not convert from ISO-8859-1 to UTF-8.
jas@latte:~$
The simplest explanation is that you haven't installed the iconv conversion tools. You can find it as a standalone library in GNU Libiconv (http://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 (e.g., glibc-locale for Debian) to be able to use it.
Another explanation is that the error is correct and you are feeding
idn invalid data. This can happen inadvertently if you are not
careful with the character set encodings you use. For example, if
your shell run in a ISO-8859-1 environment, and you invoke
idn with the CHARSET 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 parsable as 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:~$ idn --quiet --debug ""
system locale uses charset `ISO-8859-1'.
jas@latte:~$ CHARSET=UTF-8 idn --quiet --debug räksmörgås
system locale uses charset `UTF-8'.
input[0] = U+0072
input[1] = U+4af3
input[2] = U+006d
input[3] = U+1b29e5
input[4] = U+0073
output[0] = U+0078
output[1] = U+006e
output[2] = U+002d
output[3] = U+002d
output[4] = U+0072
output[5] = U+006d
output[6] = U+0073
output[7] = U+002d
output[8] = U+0068
output[9] = U+0069
output[10] = U+0036
output[11] = U+0064
output[12] = U+0035
output[13] = U+0039
output[14] = U+0037
output[15] = U+0035
output[16] = U+0035
output[17] = U+0032
output[18] = U+0061
xn--rms-hi6d597552a
jas@latte:~$
The sense moral here is to forget about CHARSET (configure your locales properly instead) unless you know what you are doing, and if you want to use it, do it carefully, after verifying with --debug that you get the desired results.
Included in Libidn are punycode.el and idna.el that
provides an Emacs Lisp API to (a limited set of) the Libidn API. This
section describes the API. Currently the IDNA API always set the
UseSTD3ASCIIRules flag and clear the AllowUnassigned
flag, in the future there may be functionality to specify these flags
via the API.
Name of the GNU Libidn idn application. The default is idn. This variable can be customized.
List of environment variable definitions prepended to process-environment. The default is ("CHARSET=UTF-8"). This variable can be customized.
List of parameters passed to punycode-program to invoke punycode encoding mode. The default is ("--quiet" "--punycode-encode"). This variable can be customized.
Parameters passed to punycode-program to invoke punycode decoding mode. The default is ("--quiet" "--punycode-decode"). This variable can be customized.
Returns a Punycode encoding of the string, after converting the input into UTF-8.
Returns a possibly multibyte string which is the decoding of the string which is a punycode encoded string.
Name of the GNU Libidn idn application. The default is idn. This variable can be customized.
List of environment variable definitions prepended to process-environment. The default is ("CHARSET=UTF-8"). This variable can be customized.
List of parameters passed to idna-program to invoke IDNA ToASCII mode. The default is ("--quiet" "--idna-to-ascii" "--usestd3asciirules"). This variable can be customized.
Parameters passed idna-program to invoke IDNA ToUnicode mode. The default is ("--quiet" "--idna-to-unicode" "--usestd3asciirules"). This variable can be customized.
Returns an ASCII Compatible Encoding (ACE) of the string computed by the IDNA ToASCII operation on the input string, after converting the input to UTF-8.
Returns a possibly multibyte string which is the output of the IDNA ToUnicode operation computed on the input string.
The punycode code was taken from the IETF IDN Punycode specification, by Adam M. Costello. The TLD code was contributed by Thomas Jacob. The Java implementation was contributed by Oliver Hitz. The Unicode tables were provided by Unicode, Inc. Some functions for dealing with Unicode (see nfkc.c and toutf8.c) has been borrowed from GLib downloaded from www.gtk.org.
Several people reported bugs, sent patches or suggested improvements, see the file THANKS in the top-level directory of the source code.
idn: Invoking idnidna-to-ascii: Emacs APIidna-to-unicode: Emacs APIidna_to_ascii_4i: IDNA Functionsidna_to_ascii_4z: IDNA Functionsidna_to_ascii_8z: IDNA Functionsidna_to_ascii_lz: IDNA Functionsidna_to_unicode_44i: IDNA Functionsidna_to_unicode_4z4z: IDNA Functionsidna_to_unicode_8z4z: IDNA Functionsidna_to_unicode_8z8z: IDNA Functionsidna_to_unicode_8zlz: IDNA Functionsidna_to_unicode_lzlz: IDNA Functionspunycode-decode: Emacs APIpunycode-encode: Emacs APIpunycode_decode: Punycode Functionspunycode_encode: Punycode Functionsstringprep: Stringprep Functionsstringprep_4i: Stringprep Functionsstringprep_4zi: Stringprep Functionsstringprep_check_version: Version Checkstringprep_convert: Utility Functionsstringprep_iscsi: Stringprep Functionsstringprep_locale_charset: Utility Functionsstringprep_locale_to_utf8: Utility Functionsstringprep_nameprep_no_unassigned: Stringprep Functionsstringprep_plain: Stringprep Functionsstringprep_profile: Stringprep Functionsstringprep_ucs4_nfkc_normalize: Utility Functionsstringprep_ucs4_to_utf8: Utility Functionsstringprep_unichar_to_utf8: Utility Functionsstringprep_utf8_nfkc_normalize: Utility Functionsstringprep_utf8_to_locale: Utility Functionsstringprep_utf8_to_ucs4: Utility Functionsstringprep_utf8_to_unichar: Utility Functionsstringprep_xmpp_nodeprep: Stringprep Functionsstringprep_xmpp_resourceprep: Stringprep Functionstld_check_4: TLD Functionstld_check_4t: TLD Functionstld_check_4tz: TLD Functionstld_check_4z: TLD Functionstld_check_8z: TLD Functionstld_check_lz: TLD Functionstld_default_table: TLD Functionstld_get_4: TLD Functionstld_get_4z: TLD Functionstld_get_table: TLD Functionstld_get_z: TLD Functions Copyright © 1991, 1999 Free Software Foundation, Inc.
59 Temple Place – Suite 330, Boston, MA 02111-1307, USA
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307,
USA.
Also add information on how to contact you by electronic and paper mail.
You should also get your employer (if you work as a programmer) or your school, if any, to sign a “copyright disclaimer” for the library, if necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the library
`Frob' (a library for tweaking knobs) written by James Random Hacker.
signature of Ty Coon, 1 April 1990
Ty Coon, President of Vice
That's all there is to it!
Copyright © 2000,2001,2002 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA 02111-1307, USA
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To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:
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Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this:
with the Invariant Sections being list their titles, with
the Front-Cover Texts being list, and with the Back-Cover Texts
being list.
If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.
If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.