Valid-License-Identifier: LGPL-2.1
Valid-License-Identifier: LGPL-2.1-only
Valid-License-Identifier: LGPL-2.1+
Valid-License-Identifier: LGPL-2.1-or-later
SPDX-URL: https://spdx.org/licenses/LGPL-2.1.html
Usage-Guide:
  To use this license in source code, put one of the following SPDX
  tag/value pairs into a comment according to the placement
  guidelines in the licensing rules documentation.
  For 'GNU Lesser General Public License (LGPL) version 2.1 only' use:
    SPDX-License-Identifier: LGPL-2.1
  For 'GNU Lesser General Public License (LGPL) version 2.1 or any later
  version' use:
    SPDX-License-Identifier: LGPL-2.1+
License-Text:

GNU LESSER GENERAL PUBLIC LICENSE
Version 2.1, February 1999

Copyright (C) 1991, 1999 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.

[This is the first released version of the Lesser GPL. It also counts as
the successor of the GNU Library Public License, version 2, hence the
version number 2.1.]

Preamble

The licenses for most software are designed to take away your freedom to
share and change it. By contrast, the GNU General Public Licenses are
intended to guarantee your freedom to share and change free software--to
make sure the software is free for all its users.

This license, the Lesser General Public License, applies to some specially
designated software packages--typically libraries--of the Free Software
Foundation and other authors who decide to use it. You can use it too, but
we suggest you first think carefully about whether this license or the
ordinary General Public License is the better strategy to use in any
particular case, based on the explanations below.

When we speak of free software, we are referring to freedom of use, not
price. Our General Public Licenses are designed to make sure that you have
the freedom to distribute copies of free software (and charge for this
service if you wish); that you receive source code or can get it if you
want it; that you can change the software and use pieces of it in new free
programs; and that you are informed that you can do these things.

To protect your rights, we need to make restrictions that forbid
distributors to deny you these rights or to ask you to surrender these
rights. These restrictions translate to certain responsibilities for you if
you distribute copies of the library or if you modify it.

For example, if you distribute copies of the library, whether gratis or for
a fee, you must give the recipients all the rights that we gave you. You
must make sure that they, too, receive or can get the source code. If you
link other code with the library, you must provide complete object files to
the recipients, so that they can relink them with the library after making
changes to the library and recompiling it. And you must show them these
terms so they know their rights.

We protect your rights with a two-step method: (1) we copyright the
library, and (2) we offer you this license, which gives you legal
permission to copy, distribute and/or modify the library.

To protect each distributor, we want to make it very clear that there is no
warranty for the free library. Also, if the library is modified by someone
else and passed on, the recipients should know that what they have is not
the original version, so that the original author's reputation will not be
affected by problems that might be introduced by others.

Finally, software patents pose a constant threat to the existence of any
free program. We wish to make sure that a company cannot effectively
restrict the users of a free program by obtaining a restrictive license
from a patent holder. Therefore, we insist that any patent license obtained
for a version of the library must be consistent with the full freedom of
use specified in this license.

Most GNU software, including some libraries, is covered by the ordinary GNU
General Public License. This license, the GNU Lesser General Public
License, applies to certain designated libraries, and is quite different
from the ordinary General Public License. We use this license for certain
libraries in order to permit linking those libraries into non-free
programs.

When a program is linked with a library, whether statically or using a
shared library, the combination of the two is legally speaking a combined
work, a derivative of the original library. The ordinary General Public
License therefore permits such linking only if the entire combination fits
its criteria of freedom. The Lesser General Public License permits more lax
criteria for linking other code with the library.

We call this license the "Lesser" General Public License because it does
Less to protect the user's freedom than the ordinary General Public
License. It also provides other free software developers Less of an
advantage over competing non-free programs. These disadvantages are the
reason we use the ordinary General Public License for many
libraries. However, the Lesser license provides advantages in certain
special circumstances.

For example, on rare occasions, there may be a special need to encourage
the widest possible use of a certain library, so that it becomes a de-facto
standard. To achieve this, non-free programs must be allowed to use the
library. A more frequent case is that a free library does the same job as
widely used non-free libraries. In this case, there is little to gain by
limiting the free library to free software only, so we use the Lesser
General Public License.

In other cases, permission to use a particular library in non-free programs
enables a greater number of people to use a large body of free
software. For example, permission to use the GNU C Library in non-free
programs enables many more people to use the whole GNU operating system, as
well as its variant, the GNU/Linux operating system.

Although the Lesser General Public License is Less protective of the users'
freedom, it does ensure that the user of a program that is linked with the
Library has the freedom and the wherewithal to run that program using a
modified version of the Library.

The precise terms and conditions for copying, distribution and modification
follow. Pay close attention to the difference between a "work based on the
library" and a "work that uses the library". The former contains code
derived from the library, whereas the latter must be combined with the
library in order to run.

TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

0. This License Agreement applies to any software library or other program
   which contains a notice placed by the copyright holder or other
   authorized party saying it may be distributed under the terms of this
   Lesser General Public License (also called "this License"). Each
   licensee is addressed as "you".

   A "library" means a collection of software functions and/or data
   prepared so as to be conveniently linked with application programs
   (which use some of those functions and data) to form executables.

   The "Library", below, refers to any such software library or work which
   has been distributed under these terms. A "work based on the Library"
   means either the Library or any derivative work under copyright law:
   that is to say, a work containing the Library or a portion of it, either
   verbatim or with modifications and/or translated straightforwardly into
   another language. (Hereinafter, translation is included without
   limitation in the term "modification".)

   "Source code" for a work means the preferred form of the work for making
   modifications to it. For a library, complete source code means all the
   source code for all modules it contains, plus any associated interface
   definition files, plus the scripts used to control compilation and
   installation of the library.

    Activities other than copying, distribution and modification are not
    covered by this License; they are outside its scope. The act of running
    a program using the Library is not restricted, and output from such a
    program is covered only if its contents constitute a work based on the
    Library (independent of the use of the Library in a tool for writing
    it). Whether that is true depends on what the Library does and what the
    program that uses the Library does.

1. You may copy and distribute verbatim copies of the Library's complete
   source code as you receive it, in any medium, provided that you
   conspicuously and appropriately publish on each copy an appropriate
   copyright notice and disclaimer of warranty; keep intact all the notices
   that refer to this License and to the absence of any warranty; and
   distribute a copy of this License along with the Library.

   You may charge a fee for the physical act of transferring a copy, and
   you may at your option offer warranty protection in exchange for a fee.

2. You may modify your copy or copies of the Library or any portion of it,
   thus forming a work based on the Library, and copy and distribute such
   modifications or work under the terms of Section 1 above, provided that
   you also meet all of these conditions:

   a) The modified work must itself be a software library.

   b) You must cause the files modified to carry prominent notices stating
      that you changed the files and the date of any change.

   c) You must cause the whole of the work to be licensed at no charge to
      all third parties under the terms of this License.

   d) If a facility in the modified Library refers to a function or a table
      of data to be supplied by an application program that uses the
      facility, other than as an argument passed when the facility is
      invoked, then you must make a good faith effort to ensure that, in
      the event an application does not supply such function or table, the
      facility still operates, and performs whatever part of its purpose
      remains meaningful.

   (For example, a function in a library to compute square roots has a
    purpose that is entirely well-defined independent of the
    application. Therefore, Subsection 2d requires that any
    application-supplied function or table used by this function must be
    optional: if the application does not supply it, the square root
    function must still compute square roots.)

   These requirements apply to the modified work as a whole. If
   identifiable sections of that work are not derived from the Library, and
   can be reasonably considered independent and separate works in
   themselves, then this License, and its terms, do not apply to those
   sections when you distribute them as separate works. But when you
   distribute the same sections as part of a whole which is a work based on
   the Library, the distribution of the whole must be on the terms of this
   License, whose permissions for other licensees extend to the entire
   whole, and thus to each and every part regardless of who wrote it.

   Thus, it is not the intent of this section to claim rights or contest
   your rights to work written entirely by you; rather, the intent is to
   exercise the right to control the distribution of derivative or
   collective works based on the Library.

   In addition, mere aggregation of another work not based on the Library
   with the Library (or with a work based on the Library) on a volume of a
   storage or distribution medium does not bring the other work under the
   scope of this License.

3. You may opt to apply the terms of the ordinary GNU General Public
   License instead of this License to a given copy of the Library. To do
   this, you must alter all the notices that refer to this License, so that
   they refer to the ordinary GNU General Public License, version 2,
   instead of to this License. (If a newer version than version 2 of the
   ordinary GNU General Public License has appeared, then you can specify
   that version instead if you wish.) Do not make any other change in these
   notices.

   Once this change is made in a given copy, it is irreversible for that
   copy, so the ordinary GNU General Public License applies to all
   subsequent copies and derivative works made from that copy.

   This option is useful when you wish to copy part of the code of the
   Library into a program that is not a library.

4. You may copy and distribute the Library (or a portion or derivative of
   it, under Section 2) in object code or executable form under the terms
   of Sections 1 and 2 above provided that you accompany it with the
   complete corresponding machine-readable source code, which must be
   distributed under the terms of Sections 1 and 2 above on a medium
   customarily used for software interchange.

   If distribution of object code is made by offering access to copy from a
   designated place, then offering equivalent access to copy the source
   code from the same place satisfies the requirement to distribute the
   source code, even though third parties are not compelled to copy the
   source along with the object code.

5. A program that contains no derivative of any portion of the Library, but
   is designed to work with the Library by being compiled or linked with
   it, is called a "work that uses the Library". Such a work, in isolation,
   is not a derivative work of the Library, and therefore falls outside the
   scope of this License.

   However, linking a "work that uses the Library" with the Library creates
   an executable that is a derivative of the Library (because it contains
   portions of the Library), rather than a "work that uses the
   library". The executable is therefore covered by this License. Section 6
   states terms for distribution of such executables.

   When a "work that uses the Library" uses material from a header file
   that is part of the Library, the object code for the work may be a
   derivative work of the Library even though the source code is
   not. Whether this is true is especially significant if the work can be
   linked without the Library, or if the work is itself a library. The
   threshold for this to be true is not precisely defined by law.

   If such an object file uses only numerical parameters, data structure
   layouts and accessors, and small macros and small inline functions (ten
   lines or less in length), then the use of the object file is
   unrestricted, regardless of whether it is legally a derivative
   work. (Executables containing this object code plus portions of the
   Library will still fall under Section 6.)

   Otherwise, if the work is a derivative of the Library, you may
   distribute the object code for the work under the terms of Section
   6. Any executables containing that work also fall under Section 6,
   whether or not they are linked directly with the Library itself.

6. As an exception to the Sections above, you may also combine or link a
   "work that uses the Library" with the Library to produce a work
   containing portions of the Library, and distribute that work under terms
   of your choice, provided that the terms permit modification of the work
   for the customer's own use and reverse engineering for debugging such
   modifications.

   You must give prominent notice with each copy of the work that the
   Library is used in it and that the Library and its use are covered by
   this License. You must supply a copy of this License. If the work during
   execution displays copyright notices, you must include the copyright
   notice for the Library among them, as well as a reference directing the
   user to the copy of this License. Also, you must do one of these things:

   a) Accompany the work with the complete corresponding machine-readable
      source code for the Library including whatever changes were used in
      the work (which must be distributed under Sections 1 and 2 above);
      and, if the work is an executable linked with the Library, with the
      complete machine-readable "work that uses the Library", as object
      code and/or source code, so that the user can modify the Library and
      then relink to produce a modified executable containing the modified
      Library. (It is understood that the user who changes the contents of
      definitions files in the Library will not necessarily be able to
      recompile the application to use the modified definitions.)

   b) Use a suitable shared library mechanism for linking with the
      Library. A suitable mechanism is one that (1) uses at run time a copy
      of the library already present on the user's computer system, rather
      than copying library functions into the executable, and (2) will
      operate properly with a modified version of the library, if the user
      installs one, as long as the modified version is interface-compatible
      with the version that the work was made with.

   c) Accompany the work with a written offer, valid for at least three
      years, to give the same user the materials specified in Subsection
      6a, above, for a charge no more than the cost of performing this
      distribution.

   d) If distribution of the work is made by offering access to copy from a
      designated place, offer equivalent access to copy the above specified
      materials from the same place.

   e) Verify that the user has already received a copy of these materials
      or that you have already sent this user a copy.

   For an executable, the required form of the "work that uses the Library"
   must include any data and utility programs needed for reproducing the
   executable from it. However, as a special exception, the materials to be
   distributed need not include anything that is normally distributed (in
   either source or binary form) with the major components (compiler,
   kernel, and so on) of the operating system on which the executable runs,
   unless that component itself accompanies the executable.

   It may happen that this requirement contradicts the license restrictions
   of other proprietary libraries that do not normally accompany the
   operating system. Such a contradiction means you cannot use both them
   and the Library together in an executable that you distribute.

7. You may place library facilities that are a work based on the Library
   side-by-side in a single library together with other library facilities
   not covered by this License, and distribute such a combined library,
   provided that the separate distribution of the work based on the Library
   and of the other library facilities is otherwise permitted, and provided
   that you do these two things:

   a) Accompany the combined library with a copy of the same work based on
      the Library, uncombined with any other library facilities. This must
      be distributed under the terms of the Sections above.

   b) Give prominent notice with the combined library of the fact that part
      of it is a work based on the Library, and explaining where to find
      the accompanying uncombined form of the same work.

8. You may not copy, modify, sublicense, link with, or distribute the
   Library except as expressly provided under this License. Any attempt
   otherwise to copy, modify, sublicense, link with, or distribute the
   Library is void, and will automatically terminate your rights under this
   License. However, parties who have received copies, or rights, from you
   under this License will not have their licenses terminated so long as
   such parties remain in full compliance.

9. You are not required to accept this License, since you have not signed
   it. However, nothing else grants you permission to modify or distribute
   the Library or its derivative works. These actions are prohibited by law
   if you do not accept this License. Therefore, by modifying or
   distributing the Library (or any work based on the Library), you
   indicate your acceptance of this License to do so, and all its terms and
   conditions for copying, distributing or modifying the Library or works
   based on it.

10. Each time you redistribute the Library (or any work based on the
    Library), the recipient automatically receives a license from the
    original licensor to copy, distribute, link with or modify the Library
    subject to these terms and conditions. You may not impose any further
    restrictions on the recipients' exercise of the rights granted
    herein. You are not responsible for enforcing compliance by third
    parties with this License.

11. If, as a consequence of a court judgment or allegation of patent
    infringement or for any other reason (not limited to patent issues),
    conditions are imposed on you (whether by court order, agreement or
    otherwise) that contradict the conditions of this License, they do not
    excuse you from the conditions of this License. If you cannot
    distribute so as to satisfy simultaneously your obligations under this
    License and any other pertinent obligations, then as a consequence you
    may not distribute the Library at all. For example, if a patent license
    would not permit royalty-free redistribution of the Library by all
    those who receive copies directly or indirectly through you, then the
    only way you could satisfy both it and this License would be to refrain
    entirely from distribution of the Library.

    If any portion of this section is held invalid or unenforceable under
    any particular circumstance, the balance of the section is intended to
    apply, and the section as a whole is intended to apply in other
    circumstances.

    It is not the purpose of this section to induce you to infringe any
    patents or other property right claims or to contest validity of any
    such claims; this section has the sole purpose of protecting the
    integrity of the free software distribution system which is implemented
    by public license practices. Many people have made generous
    contributions to the wide range of software distributed through that
    system in reliance on consistent application of that system; it is up
    to the author/donor to decide if he or she is willing to distribute
    software through any other system and a licensee cannot impose that
    choice.

    This section is intended to make thoroughly clear what is believed to
    be a consequence of the rest of this License.

12. If the distribution and/or use of the Library is restricted in certain
    countries either by patents or by copyrighted interfaces, the original
    copyright holder who places the Library under this License may add an
    explicit geographical distribution limitation excluding those
    countries, so that distribution is permitted only in or among countries
    not thus excluded. In such case, this License incorporates the
    limitation as if written in the body of this License.

13. The Free Software Foundation may publish revised and/or new versions of
    the Lesser General Public License from time to time. Such new versions
    will be similar in spirit to the present version, but may differ in
    detail to address new problems or concerns.

    Each version is given a distinguishing version number. If the Library
    specifies a version number of this License which applies to it and "any
    later version", you have the option of following the terms and
    conditions either of that version or of any later version published by
    the Free Software Foundation. If the Library does not specify a license
    version number, you may choose any version ever published by the Free
    Software Foundation.

14. If you wish to incorporate parts of the Library into other free
    programs whose distribution conditions are incompatible with these,
    write to the author to ask for permission. For software which is
    copyrighted by the Free Software Foundation, write to the Free Software
    Foundation; we sometimes make exceptions for this. Our decision will be
    guided by the two goals of preserving the free status of all
    derivatives of our free software and of promoting the sharing and reuse
    of software generally.

NO WARRANTY

15. BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
    FOR THE LIBRARY, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
    OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
    PROVIDE THE LIBRARY "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
    EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
    ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE LIBRARY IS WITH
    YOU. SHOULD THE LIBRARY PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
    NECESSARY SERVICING, REPAIR OR CORRECTION.

16. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
    WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
    REDISTRIBUTE THE LIBRARY AS PERMITTED ABOVE, BE LIABLE TO YOU FOR
    DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL
    DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE LIBRARY
    (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED
    INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF
    THE LIBRARY TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR
    OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Libraries

If you develop a new library, and you want it to be of the greatest
possible use to the public, we recommend making it free software that
everyone can redistribute and change. You can do so by permitting
redistribution under these terms (or, alternatively, under the terms of the
ordinary General Public License).

To apply these terms, attach the following notices to the library. It is
safest to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least the
"copyright" line and a pointer to where the full notice is found.

one line to give the library's name and an idea of what it does.
Copyright (C) year name of author

This library 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.

This library 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 this library; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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!