fix bug in bitcount helper, fixes graphhopper#809

Author: karussell

core/src/main/java/com/graphhopper/util/Helper.java

@@ -88,11 +88,15 @@ static String packageToPath(Package pkg) {
     }
 
     public static int countBitValue(int maxTurnCosts) {
-        double val = Math.log(maxTurnCosts) / Math.log(2);
-        int intVal = (int) val;
-        if (val == intVal)
-            return intVal;
-        return intVal + 1;
+        if (maxTurnCosts < 0)
+            throw new IllegalArgumentException("maxTurnCosts cannot be negative " + maxTurnCosts);
+
+        int counter = 0;
+        while (maxTurnCosts > 0) {
+            maxTurnCosts >>= 1;
+            counter++;
+        }
+        return counter++;
     }
 
     public static void loadProperties(Map<String, String> map, Reader tmpReader) throws IOException {

core/src/test/java/com/graphhopper/util/HelperTest.java

@@ -47,7 +47,12 @@ public void tearDown() {
 
     @Test
     public void testCountBitValue() throws Exception {
-        assertEquals(2, Helper.countBitValue(4));
+        assertEquals(1, Helper.countBitValue(1));
+        assertEquals(2, Helper.countBitValue(2));
+        assertEquals(2, Helper.countBitValue(3));
+        assertEquals(3, Helper.countBitValue(4));
+        assertEquals(3, Helper.countBitValue(7));
+        assertEquals(4, Helper.countBitValue(8));
         assertEquals(5, Helper.countBitValue(20));
     }