1 /* 2 * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 24 /* 25 * @test 26 * @bug 4495754 27 * @summary Basic test for int bit twiddling 28 * @author Josh Bloch 29 * @key randomness 30 */ 31 32 import java.util.Random; 33 import static java.lang.Integer.*; 34 35 public class BitTwiddle { 36 private static final int N = 1000; // # of repetitions per test 37 38 public static void main(String args[]) { 39 Random rnd = new Random(); 40 41 if (highestOneBit(0) != 0) 42 throw new RuntimeException("a"); 43 if (highestOneBit(-1) != MIN_VALUE) 44 throw new RuntimeException("b"); 45 if (highestOneBit(1) != 1) 46 throw new RuntimeException("c"); 47 48 if (lowestOneBit(0) != 0) 49 throw new RuntimeException("d"); 50 if (lowestOneBit(-1) != 1) 51 throw new RuntimeException("e"); 52 if (lowestOneBit(MIN_VALUE) != MIN_VALUE) 53 throw new RuntimeException("f"); 54 55 for (int i = 0; i < N; i++) { 56 int x = rnd.nextInt(); 57 if (highestOneBit(x) != reverse(lowestOneBit(reverse(x)))) 58 throw new RuntimeException("g: " + toHexString(x)); 59 } 60 61 if (numberOfLeadingZeros(0) != SIZE) 62 throw new RuntimeException("h"); 63 if (numberOfLeadingZeros(-1) != 0) 64 throw new RuntimeException("i"); 65 if (numberOfLeadingZeros(1) != (SIZE - 1)) 66 throw new RuntimeException("j"); 67 68 if (numberOfTrailingZeros(0) != SIZE) 69 throw new RuntimeException("k"); 70 if (numberOfTrailingZeros(1) != 0) 71 throw new RuntimeException("l"); 72 if (numberOfTrailingZeros(MIN_VALUE) != (SIZE - 1)) 73 throw new RuntimeException("m"); 74 75 for (int i = 0; i < N; i++) { 76 int x = rnd.nextInt(); 77 if (numberOfLeadingZeros(x) != numberOfTrailingZeros(reverse(x))) 78 throw new RuntimeException("n: " + toHexString(x)); 79 } 80 81 if (bitCount(0) != 0) 82 throw new RuntimeException("o"); 83 84 for (int i = 0; i < SIZE; i++) { 85 int pow2 = 1 << i; 86 if (bitCount(pow2) != 1) 87 throw new RuntimeException("p: " + i); 88 if (bitCount(pow2 -1) != i) 89 throw new RuntimeException("q: " + i); 90 } 91 92 for (int i = 0; i < N; i++) { 93 int x = rnd.nextInt(); 94 if (bitCount(x) != bitCount(reverse(x))) 95 throw new RuntimeException("r: " + toHexString(x)); 96 } 97 98 for (int i = 0; i < N; i++) { 99 int x = rnd.nextInt(); 100 int dist = rnd.nextInt(); 101 if (bitCount(x) != bitCount(rotateRight(x, dist))) 102 throw new RuntimeException("s: " + toHexString(x) + 103 toHexString(dist)); 104 if (bitCount(x) != bitCount(rotateLeft(x, dist))) 105 throw new RuntimeException("t: " + toHexString(x) + 106 toHexString(dist)); 107 if (rotateRight(x, dist) != rotateLeft(x, -dist)) 108 throw new RuntimeException("u: " + toHexString(x) + 109 toHexString(dist)); 110 if (rotateRight(x, -dist) != rotateLeft(x, dist)) 111 throw new RuntimeException("v: " + toHexString(x) + 112 toHexString(dist)); 113 } 114 115 if (signum(0) != 0 || signum(1) != 1 || signum(-1) != -1 116 || signum(MIN_VALUE) != -1 || signum(MAX_VALUE) != 1) 117 throw new RuntimeException("w"); 118 119 for (int i = 0; i < N; i++) { 120 int x = rnd.nextInt(); 121 int sign = (x < 0 ? -1 : (x == 0 ? 0 : 1)); 122 if (signum(x) != sign) 123 throw new RuntimeException("x: " + toHexString(x)); 124 } 125 126 if(reverseBytes(0xaabbccdd) != 0xddccbbaa) 127 throw new RuntimeException("y"); 128 129 for (int i = 0; i < N; i++) { 130 int x = rnd.nextInt(); 131 if (bitCount(x) != bitCount(reverseBytes(x))) 132 throw new RuntimeException("z: " + toHexString(x)); 133 } 134 } 135 }