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/* sxiv: exif.c
* Copyright (c) 2012 Bert Muennich <be.muennich at googlemail.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* This program 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#define _POSIX_C_SOURCE 200112L
#include <stdlib.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
#include "exif.h"
#include "util.h"
ssize_t s_read(int fd, const char *fn, void *buf, size_t n) {
ssize_t ret;
ret = read(fd, buf, n);
if (ret < n) {
warn("unexpected end-of-file: %s", fn);
return -1;
} else {
return ret;
}
}
unsigned short btous(unsigned char *buf, byteorder_t order) {
if (buf == NULL)
return 0;
if (order == BO_BIG_ENDIAN)
return buf[0] << 8 | buf[1];
else
return buf[1] << 8 | buf[0];
}
unsigned int btoui(unsigned char *buf, byteorder_t order) {
if (buf == NULL)
return 0;
if (order == BO_BIG_ENDIAN)
return buf[0] << 24 | buf[1] << 16 | buf[2] << 8 | buf[3];
else
return buf[3] << 24 | buf[2] << 16 | buf[1] << 8 | buf[0];
}
int exif_orientation(const fileinfo_t *file) {
int fd;
unsigned char data[EXIF_MAX_LEN];
byteorder_t order = BO_BIG_ENDIAN;
unsigned int cnt, len, idx, val;
if (file == NULL || file->path == NULL)
return -1;
fd = open(file->path, O_RDONLY);
if (fd < 0)
return -1;
if (s_read(fd, file->name, data, 4) < 0)
goto abort;
if (btous(data, order) != JPEG_MARKER_SOI)
goto abort;
if (btous(data + 2, order) != JPEG_MARKER_APP1)
goto abort;
if (s_read(fd, file->name, data, 2) < 0)
goto abort;
len = btous(data, order);
if (len < 8)
goto abort;
if (s_read(fd, file->name, data, 6) < 0)
goto abort;
if (btoui(data, order) != EXIF_HEAD)
goto abort;
len -= 8;
if (len < 12 || len > EXIF_MAX_LEN)
goto abort;
if (s_read(fd, file->name, data, len) < 0)
goto abort;
switch (btous(data, order)) {
case EXIF_BO_BIG_ENDIAN:
order = BO_BIG_ENDIAN;
break;
case EXIF_BO_LITTLE_ENDIAN:
order = BO_LITTLE_ENDIAN;
break;
default:
goto abort;
break;
}
if (btous(data + 2, order) != EXIF_TAG_MARK)
goto abort;
idx = btoui(data + 4, order);
if (idx > len - 2)
goto abort;
val = 0;
cnt = btous(data + idx, order);
for (idx += 2; cnt > 0 && idx < len - 12; cnt--, idx += 12) {
if (btous(data + idx, order) == EXIF_TAG_ORIENTATION) {
val = btous(data + idx + 8, order);
break;
}
}
close(fd);
return val;
abort:
close(fd);
return -1;
}
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