52 lines
1.3 KiB
Java
52 lines
1.3 KiB
Java
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/* Copyright <EFBFBD> 2000 Free Software Foundation
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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package gnu.gcj.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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