69 lines
2.2 KiB
Java
69 lines
2.2 KiB
Java
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/* Copyright (C) 2000, 2002 Free Software Foundation
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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As a special exception, if you link this library with other files to
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produce an executable, this library does not by itself cause the
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resulting executable to be covered by the GNU General Public License.
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This exception does not however invalidate any other reasons why the
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executable file might be covered by the GNU General Public License. */
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package gnu.java.awt;
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/**
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* Simple transparent utility class that can be used to perform bit
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* mask extent calculations.
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*/
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public final class BitMaskExtent
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{
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/** The number of the least significant bit of the bit mask extent. */
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public byte leastSignificantBit;
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/** The number of bits in the bit mask extent. */
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public byte bitWidth;
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/**
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* Set the bit mask. This will calculate and set the leastSignificantBit
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* and bitWidth fields.
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*
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* @see #leastSignificantBit
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* @see #bitWidth
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*/
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public void setMask(long mask)
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{
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leastSignificantBit = 0;
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bitWidth = 0;
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if (mask == 0) return;
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long shiftMask = mask;
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for (; (shiftMask&1) == 0; shiftMask >>>=1) leastSignificantBit++;
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for (; (shiftMask&1) != 0; shiftMask >>>=1) bitWidth++;
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if (shiftMask != 0)
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throw new IllegalArgumentException("mask must be continuous");
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}
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/**
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* Calculate the bit mask based on the values of the
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* leastSignificantBit and bitWidth fields.
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*/
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public long toMask()
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{
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return ((1<<bitWidth)-1) << leastSignificantBit;
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}
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}
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