[tracker] libtracker-extract: Fix broken EXIF GPS coordinate extraction

[Martyn James Russell <mr src gnome org>]

commit 652a137a93b4948c27696ba184ddd85fac70b62d
Author: Martyn Russell <martyn lanedo com>
Date:   Fri Aug 29 11:58:48 2014 +0100

    libtracker-extract: Fix broken EXIF GPS coordinate extraction
    
    This was causing Valgrind to report reading past memory barriers

 src/libtracker-extract/tracker-exif.c |   62 +++++++++++++++++++++++----------
 1 files changed, 43 insertions(+), 19 deletions(-)
---
diff --git a/src/libtracker-extract/tracker-exif.c b/src/libtracker-extract/tracker-exif.c
index 371b30b..3e70169 100644
--- a/src/libtracker-extract/tracker-exif.c
+++ b/src/libtracker-extract/tracker-exif.c
@@ -288,32 +288,56 @@ get_gps_coordinate (ExifData *exif,
 
        if (entry && refentry) {
                ExifByteOrder order;
-               ExifRational c1,c2,c3;
+               ExifRational degrees, minutes, seconds;
                gfloat f;
                gchar ref;
 
-               order = exif_data_get_byte_order (exif);
-               c1 = exif_get_rational (entry->data, order);
-               c2 = exif_get_rational (entry->data+8, order);
-               c3 = exif_get_rational (entry->data+16, order);
-               ref = exif_get_short (refentry->data, order);
+               if (entry->size == 24) {
+                       order = exif_data_get_byte_order (exif);
+                       degrees = exif_get_rational (entry->data, order);
+                       minutes = exif_get_rational (entry->data + 8, order);
+                       seconds = 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;
-               }
+                       /* Avoid ridiculous values */
+                       if (degrees.denominator == 0 ||
+                           minutes.denominator == 0 ||
+                           seconds.denominator == 0) {
+                               return NULL;
+                       }
 
-               f = (double)c1.numerator/c1.denominator+
-                   (double)c2.numerator/(c2.denominator*60)+
-                   (double)c3.numerator/(c3.denominator*60*60);
+                       f = (gdouble) degrees.numerator / degrees.denominator +
+                               (gdouble) minutes.numerator / (minutes.denominator * 60) +
+                               (gdouble) seconds.numerator / (seconds.denominator * 60 * 60);
 
-               if (ref == 'S' || ref == 'W') {
-                       f = -1 * f;
-               }
+                       if (ref == 'S' || ref == 'W') {
+                               f = -1 * f;
+                       }
 
-               return g_strdup_printf ("%f", f);
+                       return g_strdup_printf ("%f", f);
+               } else {
+                       gchar buf[25] = { 0 };
+
+                       /* Incomplete data or it doesn't exist, fall
+                        * back to exif_entry_get_value() for safety.
+                        */
+                       exif_entry_get_value (entry, buf, sizeof (buf) - 1);
+
+                       if (buf[0] == '\0') {
+                               g_message ("EXIF GPS coordinate information is non-existent but EXIF tag '%s' 
was found, "
+                                          "possible broken EXIF data?",
+                                          exif_tag_get_name (tag));
+                       } else {
+                               g_message ("EXIF GPS coordinate information is partial, "
+                                          "got EXIF tag '%s' with value '%s', "
+                                          "expected with degrees, minutes and seconds",
+                                          exif_tag_get_name (tag),
+                                          buf);
+                       }
+
+                       g_message ("EXIF GPS coordinate information could not be extracted with tag '%s'",
+                                  exif_tag_get_name (tag));
+               }
        }
 
        return NULL;