Add SPDX license tags to source files.

This set of files are those originally written by the author of this
commit. Two files exclusively written by me are hereby dedicated to the
public domain, while some others get explicit LGPL2+ tags which were
previously implied because of their inclusion in this project.

14 files changed, 45 insertions, 5 deletions

diff --git a/.appveyor.yml b/.appveyor.yml
index 95d3df4..cb38b6b 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -1,4 +1,8 @@
 # AppVeyor CI configuration file https://www.appveyor.com/
+#
+# SPDX-FileCopyrightText: Placed into the public domain by Dan Fandrich
+# SPDX-License-Identifier: CC0-1.0
+
 image: Visual Studio 2022
 environment:
   CYGWIN_MIRROR: https://cygwin.mirror.constant.com
diff --git a/.cirrus.yml b/.cirrus.yml
index ae3eacf..dd753a5 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -1,5 +1,8 @@
 # Cirrus CI configuration
 # https://cirrus-ci.com/github/libexif/libexif
+#
+# SPDX-FileCopyrightText: Placed into the public domain by Dan Fandrich
+# SPDX-License-Identifier: CC0-1.0
 
 freebsd_task:
   name: FreeBSD
diff --git a/contrib/Makefile.am b/contrib/Makefile.am
index 7965c42..9be0755 100644
--- a/contrib/Makefile.am
+++ b/contrib/Makefile.am
@@ -1,3 +1,6 @@
+# Copyright (C) 2008 Dan Fandrich <dan@coneharvesters.com>
+# SPDX-License-Identifier: LGPL-2.0-or-later
+
 SUBDIRS = examples
 
 # The c++ and aolserver contrib directories are out of date and are
diff --git a/contrib/examples/Makefile.am b/contrib/examples/Makefile.am
index 61bb4be..d198802 100644
--- a/contrib/examples/Makefile.am
+++ b/contrib/examples/Makefile.am
@@ -1,4 +1,8 @@
 # Simple example programs
+#
+# Copyright (C) 2008-2009 Dan Fandrich <dan@coneharvesters.com>
+# SPDX-License-Identifier: LGPL-2.0-or-later
+
 check_PROGRAMS = photographer thumbnail write-exif
 
 # Example programs with dependencies other than plain libexif
diff --git a/contrib/examples/photographer.c b/contrib/examples/photographer.c
index b40df43..2f04e64 100644
--- a/contrib/examples/photographer.c
+++ b/contrib/examples/photographer.c
@@ -3,7 +3,8 @@
  * EXIF and MakerNote tags. The tags selected are those that may aid in
  * identification of the photographer who took the image.
  *
- * Placed into the public domain by Dan Fandrich
+ * SPDX-FileCopyrightText: Placed into the public domain by Dan Fandrich
+ * SPDX-License-Identifier: CC0-1.0
  */
 
 #include <stdio.h>
diff --git a/contrib/examples/thumbnail.c b/contrib/examples/thumbnail.c
index 1750d5c..3bb843b 100644
--- a/contrib/examples/thumbnail.c
+++ b/contrib/examples/thumbnail.c
@@ -2,7 +2,8 @@
  * libexif example program to extract an EXIF thumbnail from an image
  * and save it into a new file.
  *
- * Placed into the public domain by Dan Fandrich
+ * SPDX-FileCopyrightText: Placed into the public domain by Dan Fandrich
+ * SPDX-License-Identifier: CC0-1.0
  */
 
 #include <stdio.h>
diff --git a/contrib/examples/write-exif.c b/contrib/examples/write-exif.c
index bae2786..7190690 100644
--- a/contrib/examples/write-exif.c
+++ b/contrib/examples/write-exif.c
@@ -1,8 +1,6 @@
 /*
  * write-exif.c
  *
- * Placed into the public domain by Daniel Fandrich
- *
  * Create a new EXIF data block and write it into a JPEG image file.
  *
  * The JPEG image data used in this example is fixed and is guaranteed not
@@ -10,6 +8,9 @@
  * in the file the EXIF data should be. In real life, a library like
  * libjpeg (included with the exif command-line tool source code) would
  * be used to write to an existing JPEG file.
+ *
+ * SPDX-FileCopyrightText: Placed into the public domain by Dan Fandrich
+ * SPDX-License-Identifier: CC0-1.0
  */
 
 #include <stdio.h>
diff --git a/doc/footer.html b/doc/footer.html
index dd88ecd..fcc1b03 100644
--- a/doc/footer.html
+++ b/doc/footer.html
@@ -1,5 +1,6 @@
 
-
+<!-- Copyright (C) 2009-2017 Dan Fandrich <dan@coneharvesters.com>
+     SPDX-License-Identifier: LGPL-2.0-or-later -->
 <hr size="1">
 <address style="text-align: right;">
 <a href="https://libexif.github.io" target="_top">libexif</a>
diff --git a/m4m/failmalloc.m4 b/m4m/failmalloc.m4
index 73e6929..17bb12c 100644
--- a/m4m/failmalloc.m4
+++ b/m4m/failmalloc.m4
@@ -1,4 +1,8 @@
 dnl Search for libfailmalloc to use for testing
+dnl
+dnl Copyright (C) 2018-2021 Dan Fandrich <dan@coneharvesters.com>, et. al.
+dnl SPDX-License-Identifier: LGPL-2.0-or-later
+
 AC_DEFUN([CHECK_FAILMALLOC],[dnl
   dnl Libtool sets the default library paths
   LT_INIT([win32-dll])
diff --git a/m4m/stdint.m4 b/m4m/stdint.m4
index 0eca373..803320f 100644
--- a/m4m/stdint.m4
+++ b/m4m/stdint.m4
@@ -2,6 +2,9 @@ dnl AC_NEED_STDINT_H ( HEADER-TO-GENERATE )
 dnl
 dnl Look for a header file that defines size-specific integer types like the
 dnl ones recommended to be in stdint.h in the C99 standard (e.g. uint32_t).
+dnl
+dnl Copyright (C) 2001-2021 Dan Fandrich <dan@coneharvesters.com>, et. al.
+dnl SPDX-License-Identifier: LGPL-2.0-or-later
 
 dnl AX_CHECK_DEFINED_TYPE ( TYPE, FILE, ACTION-IF-FOUND, ACTION-IF-NOT-FOUND )
 dnl This is similar to _AC_CHECK_TYPE_NEW (a.k.a. new syntax version of
diff --git a/test/check-failmalloc.sh b/test/check-failmalloc.sh
index c4e26d5..ecb6513 100755
--- a/test/check-failmalloc.sh
+++ b/test/check-failmalloc.sh
@@ -10,6 +10,9 @@
 # functions that could encounter a problem. The issue could be solved in more
 # cases with more judicious use of log calls with EXIF_LOG_CODE_NO_MEMORY
 # codes.
+#
+# Copyright (C) 2018-2021 Dan Fandrich <dan@coneharvesters.com>, et. al.
+# SPDX-License-Identifier: LGPL-2.0-or-later
 
 VERBOSE=
 if [ "$1" = "-v" ] ; then
diff --git a/test/extract-parse.sh b/test/extract-parse.sh
index df93fa5..548b7de 100755
--- a/test/extract-parse.sh
+++ b/test/extract-parse.sh
@@ -2,6 +2,10 @@
 # Compares the parsed EXIF data extracted from test images with the parsed EXIF
 # data in the original images. This tests that the tag parsing and writing
 # round-trip produces an EXIF structure with the same meaning as the original.
+#
+# Copyright (C) 2019-2021 Dan Fandrich <dan@coneharvesters.com>, et. al.
+# SPDX-License-Identifier: LGPL-2.0-or-later
+
 srcdir="${srcdir:-.}"
 TMPORIGINAL="$(mktemp)"
 TMPEXTRACTED="$(mktemp)"
diff --git a/test/parse-regression.sh b/test/parse-regression.sh
index 974f183..1f97051 100755
--- a/test/parse-regression.sh
+++ b/test/parse-regression.sh
@@ -1,5 +1,9 @@
 #!/bin/sh
 # Parses test EXIF files and compares the results to that expected
+#
+# Copyright (C) 2018-2021 Dan Fandrich <dan@coneharvesters.com>, et. al.
+# SPDX-License-Identifier: LGPL-2.0-or-later
+
 srcdir="${srcdir:-.}"
 TMPLOG="$(mktemp)"
 trap 'rm -f "${TMPLOG}"' 0
diff --git a/test/swap-byte-order.sh b/test/swap-byte-order.sh
index 919482b..384d279 100755
--- a/test/swap-byte-order.sh
+++ b/test/swap-byte-order.sh
@@ -1,5 +1,9 @@
 #!/bin/sh
 # Swaps the byte order of test EXIF files and ensures the data don't change.
+#
+# Copyright (C) 2018-2021 Dan Fandrich <dan@coneharvesters.com>, et. al.
+# SPDX-License-Identifier: LGPL-2.0-or-later
+
 srcdir="${srcdir:-.}"
 TMPLOG="$(mktemp)"
 trap 'rm -f "${TMPLOG}"' 0