Source for gnu.java.awt.BitMaskExtent

   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
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  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
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  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:    */
  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:    */
  75:   public long toMask()
  76:   {
  77:     return ((1<<bitWidth)-1) << leastSignificantBit;
  78:   }
  79: }