55 lines
1.3 KiB
Java
55 lines
1.3 KiB
Java
/*******************************************************************************
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* Copyright (c) 2002 - 2006 IBM Corporation.
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* All rights reserved. This program and the accompanying materials
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* are made available under the terms of the Eclipse Public License v1.0
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* which accompanies this distribution, and is available at
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* http://www.eclipse.org/legal/epl-v10.html
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*
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* Contributors:
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* IBM Corporation - initial API and implementation
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*******************************************************************************/
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package com.ibm.wala.util.math;
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import com.ibm.wala.util.debug.Assertions;
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import com.ibm.wala.util.intset.Bits;
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/**
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*
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* simple utilities with logarithms
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*
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* @author sfink
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*/
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public class Logs {
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/**
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* @param x
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* @return true iff x == 2^n for some integral n
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*/
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public static boolean isPowerOf2(int x) {
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if (x < 0) {
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return false;
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} else {
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return Bits.populationCount(x) == 1;
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}
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}
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/**
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* @param x where x == 2^n for some integral n
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*/
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public static int log2(int x) {
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if (Assertions.verifyAssertions) {
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Assertions._assert(isPowerOf2(x));
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}
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int test = 1;
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for (int i =0 ; i<31; i++) {
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if (test == x) {
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return i;
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}
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test <<= 1;
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}
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Assertions.UNREACHABLE();
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return -1;
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}
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}
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