1 /* Copyright (C) 2000, 2002 Free Software Foundation 2 3 This file is part of GNU Classpath. 4 5 GNU Classpath is free software; you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation; either version 2, or (at your option) 8 any later version. 9 10 GNU Classpath is distributed in the hope that it will be useful, but 11 WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with GNU Classpath; see the file COPYING. If not, write to the 17 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 18 02110-1301 USA. 19 20 Linking this library statically or dynamically with other modules is 21 making a combined work based on this library. Thus, the terms and 22 conditions of the GNU General Public License cover the whole 23 combination. 24 25 As a special exception, the copyright holders of this library give you 26 permission to link this library with independent modules to produce an 27 executable, regardless of the license terms of these independent 28 modules, and to copy and distribute the resulting executable under 29 terms of your choice, provided that you also meet, for each linked 30 independent module, the terms and conditions of the license of that 31 module. An independent module is a module which is not derived from 32 or based on this library. If you modify this library, you may extend 33 this exception to your version of the library, but you are not 34 obligated to do so. If you do not wish to do so, delete this 35 exception statement from your version. */ 36 37 package gnu.java.awt; 38 39 /** 40 * Simple transparent utility class that can be used to perform bit 41 * mask extent calculations. 42 */ 43 public final class BitMaskExtent 44 { 45 /** The number of the least significant bit of the bit mask extent. */ 46 public byte leastSignificantBit; 47 48 /** The number of bits in the bit mask extent. */ 49 public byte bitWidth; 50 51 /** 52 * Set the bit mask. This will calculate and set the leastSignificantBit 53 * and bitWidth fields. 54 * 55 * @see #leastSignificantBit 56 * @see #bitWidth 57 */ setMask(long mask)58 public void setMask(long mask) 59 { 60 leastSignificantBit = 0; 61 bitWidth = 0; 62 if (mask == 0) return; 63 long shiftMask = mask; 64 for (; (shiftMask&1) == 0; shiftMask >>>=1) leastSignificantBit++; 65 for (; (shiftMask&1) != 0; shiftMask >>>=1) bitWidth++; 66 67 if (shiftMask != 0) 68 throw new IllegalArgumentException("mask must be continuous"); 69 } 70 71 /** 72 * Calculate the bit mask based on the values of the 73 * leastSignificantBit and bitWidth fields. 74 */ toMask()75 public long toMask() 76 { 77 return ((1<<bitWidth)-1) << leastSignificantBit; 78 } 79 } 80