RideCache load performance improvement

.. string manipulation using raw C since its simple character
   replacement, halved time over previous approach.

.. lookup rideitem in ridecache via binary search (lower_bound)
   rather than serial. Minor speed up.

.. Overall, loading should be noticeably quicker for most users.

src/Core/RideCache.cpp

@@ -124,12 +124,12 @@ RideCache::RideCache(Context *context) : context(context)
         }
     }
 
+    // now sort it - we need to use find on it
+    qSort(rides_.begin(), rides_.end(), rideCacheLessThan);
+
     // load the store - will unstale once cache restored
     load();
 
-    // now sort it
-    qSort(rides_.begin(), rides_.end(), rideCacheLessThan);
-
     // set model once we have the basics
     model_ = new RideCacheModel(context, this);
 
@@ -152,6 +152,20 @@ RideCache::RideCache(Context *context) : context(context)
     connect(&watcher, SIGNAL(progressValueChanged(int)), this, SLOT(progressing(int)));
 }
 
+struct comparerideitem { bool operator()(const RideItem *p1, const RideItem *p2) { return p1->dateTime < p2->dateTime; } };
+
+int
+RideCache::find(RideItem *dt)
+{
+    // use lower_bound to binary search
+    QVector<RideItem*>::const_iterator i = std::lower_bound(rides_.begin(), rides_.end(), dt, comparerideitem());
+    int index = i - rides_.begin();
+
+    // did it find the right value?
+    if (index < 0 || index >= rides_.count() || rides_.at(index)->dateTime != dt->dateTime) return -1;
+    return index;
+}
+
 RideCache::~RideCache()
 {
     exiting = true;