Use Calendar.add() instead of Calendar.roll()

Calendar.roll() breaks the year at the beginning of the year, so
use add() instead, which changes larger fields.

Also, only use 4 bins, since the last bin's boundary is not relevant.

Lastly, no need to return Calendar in beginningOfDay.

Fixes http://b/issue?id=2361382

core/java/android/webkit/DateSorter.java

@@ -38,7 +38,7 @@ public class DateSorter {
     /** must be >= 3 */
     public static final int DAY_COUNT = 5;
 
-    private long [] mBins = new long[DAY_COUNT];
+    private long [] mBins = new long[DAY_COUNT-1];
     private String [] mLabels = new String[DAY_COUNT];
     
     private static final int NUM_DAYS_AGO = 5;
@@ -54,15 +54,13 @@ public class DateSorter {
         
         // Create the bins
         mBins[0] = c.getTimeInMillis(); // Today
-        c.roll(Calendar.DAY_OF_YEAR, -1);
+        c.add(Calendar.DAY_OF_YEAR, -1);
         mBins[1] = c.getTimeInMillis();  // Yesterday
-        c.roll(Calendar.DAY_OF_YEAR, -(NUM_DAYS_AGO - 1));
+        c.add(Calendar.DAY_OF_YEAR, -(NUM_DAYS_AGO - 1));
         mBins[2] = c.getTimeInMillis();  // Five days ago
-        c.roll(Calendar.DAY_OF_YEAR, NUM_DAYS_AGO); // move back to today
-        c.roll(Calendar.MONTH, -1);
+        c.add(Calendar.DAY_OF_YEAR, NUM_DAYS_AGO); // move back to today
+        c.add(Calendar.MONTH, -1);
         mBins[3] = c.getTimeInMillis();  // One month ago
-        c.roll(Calendar.MONTH, -1);
-        mBins[4] = c.getTimeInMillis();  // Over one month ago
 
         // build labels
         mLabels[0] = context.getText(com.android.internal.R.string.today).toString();
@@ -84,11 +82,11 @@ public class DateSorter {
      * date bin this date belongs to
      */
     public int getIndex(long time) {
-        // Lame linear search
-        for (int i = 0; i < DAY_COUNT; i++) {
+        int lastDay = DAY_COUNT - 1;
+        for (int i = 0; i < lastDay; i++) {
             if (time > mBins[i]) return i;
         }
-        return DAY_COUNT - 1;
+        return lastDay;
     }
 
     /**
@@ -96,6 +94,7 @@ public class DateSorter {
      * @return string label suitable for display to user
      */
     public String getLabel(int index) {
+        if (index < 0 || index >= DAY_COUNT) return "";
         return mLabels[index];
     }
 
@@ -105,17 +104,22 @@ public class DateSorter {
      * @return date boundary at given index
      */
     public long getBoundary(int index) {
+        int lastDay = DAY_COUNT - 1;
+        // Error case
+        if (index < 0 || index > lastDay) index = 0;
+        // Since this provides a lower boundary on dates that will be included
+        // in the given bin, provide the smallest value
+        if (index == lastDay) return Long.MIN_VALUE;
         return mBins[index];
     }
 
     /**
      * Calcuate 12:00am by zeroing out hour, minute, second, millisecond
      */
-    private Calendar beginningOfDay(Calendar c) {
+    private void beginningOfDay(Calendar c) {
         c.set(Calendar.HOUR_OF_DAY, 0);
         c.set(Calendar.MINUTE, 0);
         c.set(Calendar.SECOND, 0);
         c.set(Calendar.MILLISECOND, 0);
-        return c;
     }
 }