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Adding both forms of flip() to BitSet.

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This commit is contained in:
Mike Keesey 2012-07-02 13:21:31 -06:00
parent 31311160c3
commit d419899ac1
2 changed files with 51 additions and 0 deletions
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24
classpath/java/util/BitSet.java
View File

@ -80,6 +80,30 @@ public class BitSet implements Serializable, Cloneable {
bits[i] ^= otherBits.bits[i];
}
}
public void flip(int index) {
flip(index, index+1);
}
public void flip(int fromIndex, int toIndex) {
if (fromIndex > toIndex || fromIndex < 0 || toIndex < 0) {
throw new IndexOutOfBoundsException();
} else if (fromIndex != toIndex) {
int basePartition = longPosition(fromIndex);
int lastPartition = longPosition(toIndex - 1); //range is [fromIndex, toIndex)
int numPartitionsToTraverse = lastPartition - basePartition + 1;
enlarge(lastPartition);
int currentFirstIndex = fromIndex;
for (int i = 0; i < numPartitionsToTraverse; ++i) {
int currentToIndex = Math.min(toIndex, (basePartition + i + 1) * BITS_PER_LONG);
int currentRange = currentToIndex - currentFirstIndex;
long mask = (((1L << currentRange) - 1L) << (currentFirstIndex % BITS_PER_LONG));
bits[i + basePartition] ^= mask;
currentFirstIndex = currentToIndex;
}
}
}
private void enlarge(int newSize) {
if (bits == null || bits.length < newSize) {

27
test/BitsetTest.java
View File

@ -47,6 +47,33 @@ public class BitsetTest {
assertEquals("after 5, 6 is empty", 6, bits.nextClearBit(5));
assertEquals("after 100, 102 is empty", 102, bits.nextClearBit(100));
testFlip();
}
private static void testFlip() {
/* simple case */
BitSet bitset = new BitSet();
bitset.set(0);
bitset.flip(0, 0);
assertTrue("Should not be flipped with 0 length range", bitset.get(0));
bitset.flip(0, 1);
assertTrue("Should be false with range of one", !bitset.get(0));
bitset.flip(0);
assertTrue("Should be true again", bitset.get(0));
/* need to grow */
bitset.flip(1000);
assertTrue("1000 should be true", bitset.get(1000));
assertTrue("1001 should be false", !bitset.get(1001));
assertTrue("999 should be false", !bitset.get(999));
/* Range over 2 segments */
bitset.flip(60, 70);
assertTrue("59 should be false", !bitset.get(59));
for (int i=60; i < 70; ++i) {
assertTrue(i + " should be true", bitset.get(i));
}
assertTrue("70 should be false", !bitset.get(70));
}
static void assertTrue(String msg, boolean flag) {