+/** \file test-extract.c
+ * \brief Extract EXIF data from a file and write it to another file.
+ *
+ * Copyright (C) 2019 Dan Fandrich <dan@coneharvesters.com>
+ *
+ * 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 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.
+ *
+ */
+
+#include "libexif/exif-data.h"
+
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+
+static const unsigned char header[4] = {'\xff', '\xd8', '\xff', '\xe1'};
+
+int main(const int argc, const char *argv[])
+{
+ int first = 1;
+ const char *fn = "input.jpg";
+ const char *outfn = "output.exif";
+ ExifData *d;
+ unsigned char *buf;
+ unsigned int len;
+ FILE *f;
+ unsigned char lenbuf[2];
+
+ if (argc > 1 && !strcmp(argv[1], "-o")) {
+ outfn = argv[2];
+ first += 2;
+ }
+ if (argc > first) {
+ fn = argv[first];
+ ++first;
+ }
+ if (argc > first) {
+ fprintf (stderr, "Too many arguments\n");
+ return 1;
+ }
+
+ d = exif_data_new_from_file(fn);
+ if (!d) {
+ fprintf (stderr, "Could not load data from '%s'!\n", fn);
+ return 1;
+ }
+
+ exif_data_save_data(d, &buf, &len);
+ exif_data_unref(d);
+
+ if (!buf) {
+ fprintf (stderr, "Could not extract EXIF data!\n");
+ return 2;
+ }
+
+ f = fopen(outfn, "wb");
+ if (!f) {
+ fprintf (stderr, "Could not open '%s' for writing!\n", outfn);
+ return 1;
+ }
+ /* Write EXIF with headers and length. */
+ if (fwrite(header, 1, sizeof(header), f) != sizeof(header)) {
+ fprintf (stderr, "Could not write to '%s'!\n", outfn);
+ return 3;
+ }
+ /*
+ * FIXME: The buffer from exif_data_save_data() seems to contain extra 0xffd8
+ * 0xffd9 JPEG markers at the end that I wasn't expecting, making the length
+ * seem too long. Should those markers really be included?
+ */
+ exif_set_short(lenbuf, EXIF_BYTE_ORDER_MOTOROLA, len);
+ if (fwrite(lenbuf, 1, 2, f) != 2) {
+ fprintf (stderr, "Could not write to '%s'!\n", outfn);
+ return 3;
+ }
+ if (fwrite(buf, 1, len, f) != len) {
+ fprintf (stderr, "Could not write to '%s'!\n", outfn);
+ return 3;
+ }
+ if (fclose(f) != 0) {
+ fprintf (stderr, "Could not close '%s'!\n", outfn);
+ return 3;
+ }
+ free(buf);
+ fprintf (stderr, "Wrote EXIF data to '%s'\n", outfn);
+
+ return 0;
+}