public void testIsPowerOfTwo() {
for (BigInteger x : ALL_BIGINTEGER_CANDIDATES) {
// Checks for a single bit set.
boolean expected = x.signum() > 0 & x.and(x.subtract(ONE)).equals(ZERO);
assertEquals(expected, BigIntegerMath.isPowerOfTwo(x));
}
}
public void testFloorPowerOfTwo() {
for (BigInteger x : POSITIVE_BIGINTEGER_CANDIDATES) {
BigInteger result = BigIntegerMath.floorPowerOfTwo(x);
assertTrue(BigIntegerMath.isPowerOfTwo(result));
assertTrue(result.compareTo(x) <= 0);
assertTrue(result.add(result).compareTo(x) > 0);
}
}
public void testCeilingPowerOfTwo() {
for (BigInteger x : POSITIVE_BIGINTEGER_CANDIDATES) {
BigInteger result = BigIntegerMath.ceilingPowerOfTwo(x);
assertTrue(BigIntegerMath.isPowerOfTwo(result));
assertTrue(result.compareTo(x) >= 0);
assertTrue(result.compareTo(x.add(x)) < 0);
}
}
// Relies on the correctness of isPowerOfTwo(BigInteger).
public void testLog2Exact() {
for (BigInteger x : POSITIVE_BIGINTEGER_CANDIDATES) {
// We only expect an exception if x was not a power of 2.
boolean isPowerOf2 = BigIntegerMath.isPowerOfTwo(x);
try {
assertEquals(x, ZERO.setBit(BigIntegerMath.log2(x, UNNECESSARY)));
assertTrue(isPowerOf2);
} catch (ArithmeticException e) {
assertFalse(isPowerOf2);
}
}
}
