/*******************************************************************************
* Copyright (c) 2002 - 2006 IBM Corporation.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package com.ibm.wala.util.intset;
/**
* utilities for manipulating values at the bit-level.
*/
public class Bits {
// there's no reason to instantiate this class.
private Bits() {
}
/**
* Return the lower 8 bits (as an int) of an int
*/
public static int lower8(int value) {
return (value & 0xff);
}
/**
* Return the lower 16 bits (as an int) of an int
*/
public static int lower16(int value) {
return (value & 0xffff);
}
/**
* Return the upper 16 bits (as an int) of an int
*/
public static int upper16(int value) {
return value >>> 16;
}
/**
* Return the upper 24 bits (as an int) of an int
*/
public static int upper24(int value) {
return value >>> 8;
}
/**
* Return the lower 32 bits (as an int) of a long
*/
public static int lower32(long value) {
return (int) value;
}
/**
* Return the upper 32 bits (as an int) of a long
*/
public static int upper32(long value) {
return (int) (value >>> 32);
}
/**
* Does an int literal val fit in bits bits?
*/
public static boolean fits(int val, int bits) {
val = val >> bits - 1;
return (val == 0 || val == -1);
}
/**
* Return the number of ones in the binary representation of an integer. Hank Warren's Hacker's Delight algorithm
*/
public static int populationCount(int value) {
int result = ((value & 0xAAAAAAAA) >>> 1) + (value & 0x55555555);
result = ((result & 0xCCCCCCCC) >>> 2) + (result & 0x33333333);
result = ((result & 0xF0F0F0F0) >>> 4) + (result & 0x0F0F0F0F);
result = ((result & 0xFF00FF00) >>> 8) + (result & 0x00FF00FF);
result = ((result & 0xFFFF0000) >>> 16) + (result & 0x0000FFFF);
return result;
}
}