Address Josh's review comments

Author: tedyu

unsafe/src/main/java/org/apache/spark/unsafe/bitset/BitSet.java

@@ -107,7 +107,7 @@ public int nextSetBit(int fromIndex) {
    * @return whether any bit in the BitSet is set
    */
   public boolean anySet() {
-    return BitSetMethods.anySet(baseObject, baseOffset, numWords*BitSetMethods.WORD_SIZE);
+    return BitSetMethods.anySet(baseObject, baseOffset, numWords);
   }
 
 }

unsafe/src/main/java/org/apache/spark/unsafe/bitset/BitSetMethods.java

@@ -70,11 +70,9 @@ public static boolean isSet(Object baseObject, long baseOffset, int index) {
   /**
    * Returns {@code true} if any bit is set.
    */
-  public static boolean anySet(Object baseObject, long baseOffset, long bitSetWidthInBytes) {
-    assert bitSetWidthInBytes % WORD_SIZE == 0;
-    int widthInLong = (int)(bitSetWidthInBytes / WORD_SIZE);
+  public static boolean anySet(Object baseObject, long baseOffset, long bitSetWidthInWords) {
     long addr = baseOffset;
-    for (int i = 0; i < widthInLong; i++, addr += WORD_SIZE) {
+    for (int i = 0; i < bitSetWidthInWords; i++, addr += WORD_SIZE) {
       if (PlatformDependent.UNSAFE.getLong(baseObject, addr) != 0) {
         return true;
       }

unsafe/src/test/java/org/apache/spark/unsafe/bitset/BitSetSuite.java

@@ -39,6 +39,7 @@ public void basicOps() {
     for (int i = 0; i < bs.capacity(); i++) {
       Assert.assertFalse(bs.isSet(i));
     }
+    // another form of asserting that the bit set is empty
     Assert.assertFalse(bs.anySet());
 
     // Set every bit and check it.
@@ -53,6 +54,11 @@ public void basicOps() {
       bs.unset(i);
       Assert.assertFalse(bs.isSet(i));
     }
+
+    // Make sure anySet() can detect any set bit
+    bs = createBitSet(256);
+    bs.set(64);
+    Assert.assertTrue(bs.anySet());
   }
 
   @Test