Update the licensing documentation.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

2 files changed, 62 insertions, 3 deletions

diff --git a/COPYING.md b/COPYING.md
index 8d18b6d..4174ac9 100644
--- a/COPYING.md
+++ b/COPYING.md
@@ -2,7 +2,8 @@
 
 The `libsquashfs` library is released under the terms and conditions of the
 **GNU Lesser General Public License version 3 or later**. This applies to
-all source code in the directories `lib/sqfs` and `include/sqfs`.
+all source code in the directories `lib/sqfs` and `include/sqfs`, unless
+otherwise noted.
 
 The rest of squashfs-tools-ng is released under the terms and conditions of
 the **GNU General Public License version 3 or later**.
@@ -20,6 +21,25 @@ Although the existing squashfs-tools and the Linux kernel implementation have
 been used for testing, the source code in this package is neither based on,
 nor derived from either of them.
 
+## Third Party Library Source Code
+
+The source code of `libsquashfs` incorporates modified copies of third party
+libraries that are subject to the terms and conditions of their respective
+licenses.
+
+The following is included:
+
+ - `lib/sqfs/block_processor/xxhash.c` contains a modified implementation of
+   the xxhash32 algorithm. See `licenses/xxhash.txt` for information on
+   copyright and licensing terms and conditions.
+ - `lib/sqfs/comp/lz4` contains files extracted from the LZ4 compression
+   library. See `lib/sqfs/comp/lz4/README` for details and `licenses/LZ4.txt`
+   for information on copyright and licensing terms and conditions.
+ - `lib/sqfs/comp/zlib` contains files that have been extracted from the the
+   zlib compression library and modified. See `lib/sqfs/comp/zlib/README` for
+   details and `licenses/zlib.txt` for information on copyright and licensing
+   terms and conditions.
+
 # Binary Packages with 3rd Party Libraries
 
 If this file is included in a binary release package, additional 3rd party
@@ -32,12 +52,24 @@ The following may be included:
    released under the terms and conditions of the GNU General Public License
    version 2. A copy of the license is included in `licenses/GPLv2.txt`.
  - The LZ4 compression library. Copyright Yann Collet. This is released under a
-   2 clause BSD style license, included in `licenses/LZ4.txt`.
+   2 clause BSD style license, included in `licenses/LZ4.txt`. This library may
+   be linked directly into `libsquashfs`, built from source code included in
+   the source distribution.
  - The XZ utils liblzma library is released into the public domain. An excerpt
    from the `COPYING` file of its source code archive is included
    in `licenses/xz.txt`.
  - The zlib compression library. Copyright Jean-loup Gailly and Mark Adler.
    This is released under the terms and conditions of the zlib license,
-   included in `licenses/zlib.txt`
+   included in `licenses/zlib.txt`. This library may be linked directly
+   into `libsquashfs`, built from source code included in the source
+   distribution.
  - The zstd compression library. Copyright Facebook, Inc. All rights reserved.
    This is released under a BSD style license, included in `licenses/zstd.txt`.
+
+
+Independend of build configurations, the `libsquashfs` library contains
+the following 3rd party source code, directly linked into the library:
+
+ - A modified version of the xxhash32 hash function (Copyright Yann Collet).
+   This is released under a 2-Clause BSD License. See `licenses/xxhash.txt`
+   for details.
diff --git a/licenses/xxhash.txt b/licenses/xxhash.txt
new file mode 100644
index 0000000..f2a94b0
--- /dev/null
+++ b/licenses/xxhash.txt
@@ -0,0 +1,27 @@
+xxHash - Extremely Fast Hash algorithm
+Copyright (C) 2012-2016, Yann Collet.
+
+BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+  * Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+  * Redistributions in binary form must reproduce the above
+    copyright notice, this list of conditions and the following disclaimer
+    in the documentation and/or other materials provided with the
+    distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.