Libidn FAQ -- Anticipated Frequently Asked Questions.
Copyright (C) 2002-2026 Simon Josefsson
See the end for copying conditions.

Q#1: Why doesn't Libidn use a separate library for the Unicode
     operations?

A#1: Separate libraries (Glib, QT, libiconv) seldom mark the
     Unicode tables with the corresponding Unicode version they
     implement, nor do they provide a interface where a specific
     version can be requested.  This violates the stringprep
     specification which requires that a specific version must be
     used.  Also, some of these third party libraries depend on
     non-portable behavior (e.g. threads).

Q#2: Why do Libidn include several stringprep profiles?  They waste
     space!

A#2: The stringprep profiles included are usually derived from the
     generic stringprep tables, and doesn't waste more than say a few
     hundred bytes (see profiles.c).  The Unicode normalization tables
     and the generic stringprep tables are roughly equivalent in size,
     although the latter tables can surely be compressed much further.
     They occupy about 100 kilobytes on typical platforms.  However,
     if in the future several large Stringprep profiles are added,
     configure options will be added to help reduce size.

Q#3: I thought GNU was encouraging libraries to be licensed under the GPL?

A#3: The reasoning for this was for libraries that provide unique
     functionality to encourage more free programs.  Since there are
     several IDN libraries out there, using the GPL for Libidn would
     only encourage people not to use Libidn which would not help the
     spread of free software.

Q#4: How do I add a new stringprep profile?

A#4: Add the profile definition to profiles.c, export the symbol and
     optionally add a CPP macro in stringprep.h (and document it in
     stringprep.c).  If you want to add self tests, do it through
     tst_stringprep.c.  Mention it in NEWS.

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