[tracker] libtracker-extract: Do some basic checks for GPS coordinates in EXIF tags

[Carlos Garnacho <carlosg src gnome org>]

commit 4b319b8ed06066a69feaf314c9c1cec582beb241
Author: Carlos Garnacho <carlos lanedo com>
Date:   Fri Jun 24 17:14:38 2011 +0200

    libtracker-extract: Do some basic checks for GPS coordinates in EXIF tags
    
    On some photos it would get the ExifEntries, but the coordinates wouldn't
    be meaningful, so at least check the rational numbers' denominators to
    avoid division by zero.

 src/libtracker-extract/tracker-exif.c |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)
---
diff --git a/src/libtracker-extract/tracker-exif.c b/src/libtracker-extract/tracker-exif.c
index 37fd810..280621e 100644
--- a/src/libtracker-extract/tracker-exif.c
+++ b/src/libtracker-extract/tracker-exif.c
@@ -297,7 +297,14 @@ get_gps_coordinate (ExifData *exif,
 		c2 = exif_get_rational (entry->data+8, order);
 		c3 = exif_get_rational (entry->data+16, order);
 		ref = exif_get_short (refentry->data, order);
-		
+
+		/* Avoid ridiculous values */
+		if (c1.denominator == 0 ||
+		    c2.denominator == 0 ||
+		    c3.denominator == 0) {
+			return NULL;
+		}
+
 		f = (double)c1.numerator/c1.denominator+
 		    (double)c2.numerator/(c2.denominator*60)+
 		    (double)c3.numerator/(c3.denominator*60*60);
@@ -327,6 +334,12 @@ get_gps_altitude (ExifData *exif,
 
 		order = exif_data_get_byte_order (exif);
 		c = exif_get_rational (entry->data, order);
+
+		/* Avoid ridiculous values */
+		if (c.denominator == 0) {
+			return NULL;
+		}
+
 		f = (double)c.numerator/c.denominator;
 
 		/* Strictly speaking it is invalid not to have this