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\input texinfo   @c -*-texinfo-*-
@comment $Id$
@comment %**start of header
@setfilename libidn.info
@include version.texi
@settitle GNU Libidn @value{VERSION}
@syncodeindex pg cp
@comment %**end of header
@copying
This manual is for GNU Libidn
(version @value{VERSION}, @value{UPDATED}),
which is a library for internationalized string processing.

Copyright @copyright{} 2002, 2003 Simon Josefsson.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover Texts being ``A GNU Manual,''
and with the Back-Cover Texts as in (a) below.  A copy of the
license is included in the section entitled ``GNU Free Documentation
License.''

(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
this GNU Manual, like GNU software.  Copies published by the Free
Software Foundation raise funds for GNU development.''
@end quotation
@end copying

@dircategory GNU Libraries
@direntry
* libidn: (libidn).     Internationalized string processing library.
@end direntry

@titlepage
@title GNU Libidn
@subtitle for version @value{VERSION}, @value{UPDATED}
@author Simon Josefsson (@email{bug-libidn@@gnu.org})
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@ifnottex
@node Top
@top GNU Libidn

@insertcopying
@end ifnottex

@menu
* Introduction::                How to use this manual.
* Preparation::                 What you should do before using the library.
* Stringprep Functions::        Stringprep functions.
* Punycode Functions::          Punycode functions.
* IDNA Functions::              IDNA functions.
* Examples::                    Demonstrate how to use the library.
* Acknowledgements::            Whom to blame.

Appendices

* Library Copying::             How you can copy and share GNU Libidn.
* Copying This Manual::         How you can copy and share this manual.

Indices

* Index::
@end menu


@node Introduction
@chapter Introduction

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.  It is
available under the GNU Lesser General Public License.  Currently the
Nameprep, Kerberos 5, SASL and XMPP Stringprep profiles are supported.

The library contains a generic Stringprep implementation (including
Unicode 3.2 NFKC normalization, table mapping of characters, and
Bidirectional Character handling), a few Stringprep profiles, and an
implementation of the functionality defined by Punycode and IDNA.

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.  Each stringprep
profile has a corresponding CPP macro.  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 library is used by forthcoming network applications to process
user names and passwords before they are input to cryptographic
operations.  Libidn can be built into GNU Libc to enable a new
getaddrinfo() flag for system-wide IDN processing.

GNU Libidn is developed for the GNU/Linux system, but runs on over 20
Unix platforms (including Solaris, IRIX, AIX, and Tru64) and Windows.

@menu
* Getting Started::
* Features::
* Supported Platforms::
* Bug Reports::
@end menu

@node Getting Started
@section Getting Started

This manual documents the library programming interface.  All
functions and data types provided by the library are explained.

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 (@pxref{Examples}), and then only
read up those parts of the interface which are unclear.

@node Features
@section Features

This library might have a couple of advantages over other libraries
doing a similar job.

@table @asis
@item It's Free Software
Anybody can use, modify, and redistribute it under the terms of the
GNU Lesser General Public License.

@item It's thread-safe
No global state is kept in the library.

@item It's portable
It should work on all Unix like operating systems, including Windows.

@end table

@node Supported Platforms
@section Supported Platforms

Libidn has at some point in time been tested on the following
platforms.

@enumerate

@item Debian GNU/Linux 3.0 (Woody)
@cindex Debian

GCC 2.95.4 and GNU Make. This is the main development platform.
@code{alphaev67-unknown-linux-gnu}, @code{alphaev6-unknown-linux-gnu},
@code{hppa64-unknown-linux-gnu}, @code{i686-pc-linux-gnu},
@code{ia64-unknown-linux-gnu}.

@item Tru64 UNIX
@cindex Tru64

Tru64 UNIX C compiler and Tru64 Make. @code{alphaev67-dec-osf5.1},
@code{alphaev68-dec-osf5.1}.

@item SuSE Linux 7.1
@cindex SuSE

GCC 2.96 and GNU Make. @code{alphaev6-unknown-linux-gnu},
@code{alphaev67-unknown-linux-gnu}.

@item SuSE Linux 7.2a
@cindex SuSE Linux

GCC 3.0 and GNU Make. @code{ia64-unknown-linux-gnu}.

@item RedHat Linux 7.2
@cindex RedHat

GCC 2.96 and GNU Make. @code{alphaev6-unknown-linux-gnu},
@code{alphaev67-unknown-linux-gnu}, @code{ia64-unknown-linux-gnu}.

@item RedHat Linux 8.0
@cindex RedHat

GCC 3.2 and GNU Make. @code{i686-pc-linux-gnu}.

@item RedHat Advanced Server 2.1
@cindex RedHat Advanced Server

GCC 2.96 and GNU Make. @code{i686-pc-linux-gnu}.

@item Slackware Linux 8.0.01
@cindex RedHat

GCC 2.95.3 and GNU Make. @code{i686-pc-linux-gnu}.

@item Mandrake Linux 9.0
@cindex Mandrake

GCC 3.2 and GNU Make. @code{i686-pc-linux-gnu}.

@item IRIX 6.5
@cindex IRIX

MIPS C compiler, IRIX Make. @code{mips-sgi-irix6.5}.

@item AIX 4.3.2
@cindex AIX

IBM C for AIX compiler, AIX Make.  @code{rs6000-ibm-aix4.3.2.0}.

@item Microsoft Windows 2000 (Cygwin)
@cindex Windows

GCC 3.2, GNU make. @code{i686-pc-cygwin}.

@item HP-UX 11
@cindex HP-UX

HP-UX C compiler and HP Make. @code{ia64-hp-hpux11.22},
@code{hppa2.0w-hp-hpux11.11}.

@item SUN Solaris 2.8
@cindex Solaris

Sun WorkShop Compiler C 6.0 and SUN Make. @code{sparc-sun-solaris2.8}.

@item NetBSD 1.6
@cindex NetBSD

GCC 2.95.3 and GNU Make. @code{alpha-unknown-netbsd1.6},
@code{i386-unknown-netbsdelf1.6}.

@item OpenBSD 3.1 and 3.2
@cindex OpenBSD

GCC 2.95.3 and GNU Make. @code{alpha-unknown-openbsd3.1},
@code{i386-unknown-openbsd3.1}.

@item FreeBSD 4.7
@cindex FreeBSD

GCC 2.95.4 and GNU Make. @code{alpha-unknown-freebsd4.7},
@code{i386-unknown-freebsd4.7}.

@end enumerate

If you use Libidn on, or port Libidn to, a new platform please report
it to the author.

@node Bug Reports
@section Bug Reports
@cindex Reporting Bugs

If you think you have found a bug in Libidn, please investigate it and
report it.

@itemize @bullet

@item Please make sure that the bug is really in Libidn, and
preferably also check that it hasn't already been fixed in the latest
version.

@item You have to send us a test case that makes it possible for us to
reproduce the bug.

@item You also have to explain what is wrong; if you get a crash, or
if the results printed are not good and in that case, in what way.
Make sure that the bug report includes all information you would need
to fix this kind of bug for someone else.

@end itemize

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:

@center @samp{bug-libidn@@gnu.org}


@c **********************************************************
@c *******************  Preparation  ************************
@c **********************************************************
@node Preparation
@chapter Preparation

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
(@pxref{Examples}).

@menu
* Header::
* Initialization::
* Version Check::
* Building the source::
@end menu

@node Header
@section Header

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:

@example
#include <stringprep.h>
@end example

The header files and the functions they define are categorized as
follows:

@table @asis
@item stringprep.h

The low-level stringprep API entry point.  Normal applications uses
one specific stringprep profile, and should rather include the
corresponding profile header file (see below).  If you are writing an
application that only makes use of the utility functions, including
this header file may be more appropriate however.

The name space of the stringprep part of Libidn is @code{stringprep*}
for function names, @code{Stringprep*} for data types and
@code{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.

@item stringprep_generic.h

The entry point to the generic tables specified in the stringprep
specification.  It is normally only needed by applications that want
to define its own stringprep profile, based on the generic tables.

This header file uses the same namespace as the main stringprep.h
header file.

@item stringprep_kerberos5.h

The entry point to the experimental Kerberos 5 profile of stringprep.

This header file uses the same namespace as the main stringprep.h
header file.

@item stringprep_nameprep.h

The entry point to the IDN (``nameprep'') profile of stringprep.  This
is the entry point used by applications needing low-level access to
the stringprep profile used in IDN.  Most applications requesting IDN
functionality will want idna.h instead though.

This header file uses the same namespace as the main stringprep.h
header file.

@item stringprep_plain.h

The entry point to the SASL ANONYMOUS (``plain'') profile of
stringprep.

This header file uses the same namespace as the main stringprep.h
header file.

@item stringprep_xmpp.h

The entry point to the experimental XMPP node (``nodeprep'') and
resource identifier (``resourceprep'') profiles of stringprep.

This header file uses the same namespace as the main stringprep.h
header file.

@item punycode.h

The entry point to Punycode encoding and decoding functions.  Normally
punycode is used via the idna.h interface, but some application may
want to perform raw punycode operations.

The name space of the punycode part of Libidn is @code{punycode_*} for
function names, @code{Punycode*} for data types and @code{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.

@item idna.h

The entry point to the IDNA functions.  This is the normal entry point
for applications that need IDN functionality.

The name space of the IDNA part of Libidn is @code{idna_*} for
function names, @code{Idna*} for data types and @code{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.

@end table

@node Initialization
@section Initialization

Libidn is stateless and does not need any initialization.

@node Version Check
@section Version Check

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.

@include libidn-api-version.texi

The normal way to use the function is to put something similar to the
following first in your @code{main()}:

@example
  if (!stringprep_check_version (STRINGPREP_VERSION))
    @{
      printf ("stringprep_check_version() failed:\n"
              "Header file incompatible with shared library.\n");
      exit(1);
    @}
@end example

@node Building the source
@section Building the source
@cindex Compiling your application

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 @option{-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 @command{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 @option{--cflags} option to @command{pkg-config libidn}.  The
following example shows how it can be used at the command line:

@example
gcc -c foo.c `pkg-config libidn --cflags`
@end example

Adding the output of @samp{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 @option{-L} option).  For this, the option
@option{--libs} to @command{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 @file{foo.o} with the `libidn' library to a program
@command{foo}.

@example
gcc -o foo foo.o `pkg-config libidn --libs`
@end example

Of course you can also combine both examples to a single command by
specifying both options to @command{pkg-config}:

@example
gcc -o foo foo.c `pkg-config libidn --cflags --libs`
@end example

@c **********************************************************
@c ******************  Stringprep Functions *****************
@c **********************************************************
@node Stringprep Functions
@chapter Stringprep Functions
@cindex Stringprep Functions

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.

@defcv {Enumerated type} Stringprep_profile_flags STRINGPREP_NO_NFKC
STRINGPREP_NO_NFKC disables the NFKC normalization, as well as
selecting the non-NFKC case folding tables.  Usually the profile
specifies BIDI and NFKC settings.
@end defcv

@defcv {Enumerated type} Stringprep_profile_flags STRINGPREP_NO_BIDI
STRINGPREP_NO_BIDI disables the BIDI step.  Usually the profile
specifies BIDI and NFKC settings.
@end defcv

@defcv {Enumerated type} Stringprep_profile_flags STRINGPREP_NO_UNASSIGNED
STRINGPREP_NO_UNASSIGNED causes stringprep() abort with an error if
string contains unassigned characters according to profile.
@end defcv

@include libidn-api-stringprep.texi

@c **********************************************************
@c *******************  Punycode Functions ******************
@c **********************************************************
@node Punycode Functions
@chapter Punycode Functions
@cindex Punycode Functions

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). This document defines a general algorithm called Bootstring
that 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 specified by this
document, appropriate for IDNA.

@include libidn-api-punycode.texi

@c **********************************************************
@c ********************* IDNA Functions *********************
@c **********************************************************
@node IDNA Functions
@chapter IDNA Functions
@cindex IDNA Functions

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.

@include libidn-api-idna.texi

@c **********************************************************
@c ***********************  Examples  ***********************
@c **********************************************************
@node Examples
@chapter Examples
@cindex Examples

This chapter contains example code which illustrate how `Libidn' can
be used when writing your own application.

@menu
* Example 1::           Example using stringprep.
* Example 2::           Example using punycode.
* Example 3::           Example using IDNA ToASCII.
* Example 4::           Example using IDNA ToUnicode.
@end menu

@node Example 1
@section Example 1

This example demonstrates how the stringprep functions are used.

@example
@include example.c.texi
@end example


@node Example 2
@section Example 2

This example demonstrates how the punycode functions are used.

@example
@include example2.c.texi
@end example


@node Example 3
@section Example 3

This example demonstrates how the library is used to convert
internationalized domain names into ASCII compatible names.

@example
@include example3.c.texi
@end example


@node Example 4
@section Example 4

This example demonstrates how the library is used to convert ASCII
compatible names to internationalized domain names.

@example
@include example4.c.texi
@end example

@c **********************************************************
@c *******************  Acknowledgements  *******************
@c **********************************************************
@node Acknowledgements
@chapter Acknowledgements

Simon Josefsson created the library autumn 2002 when he really should
have been studying mathematics.

The punycode code was taken from the IETF IDN Punycode specification,
by Adam M. Costello.

Some functions (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.

@include lgpl.texi

@node Copying This Manual
@appendix Copying This Manual

@menu
* GNU Free Documentation License::  License for copying this manual.
@end menu

@include fdl.texi


@node Index
@unnumbered Index

@printindex cp

@bye