1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   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.
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  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 }