mercury/java/runtime/MercuryBitmap.java at master · Mercury-Language/mercury · GitHub

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// vim: ts=4 sw=4 expandtab ft=java

// This file is distributed under the terms specified in COPYING.LIB.

package jmercury.runtime;

/**

* Simple bitmap implementation.

* This bitmap class is mainly used by bitmap.m in the standard library.

* It is also used by version_array.m which is why it is part of the

* jmercury.runtime package rather than being internal to bitmap.m.

public class MercuryBitmap implements java.io.Serializable {

public static final int BITS_PER_BYTE = 8;

public int num_bits;

public byte[] elements;

public MercuryBitmap(int numBits) {

int num_bytes = (numBits + BITS_PER_BYTE - 1) / BITS_PER_BYTE;

this.num_bits = numBits;

this.elements = new byte[num_bytes];

}

@Override

public boolean equals(Object that) {

if (this == that) {

return true;

}

if (that instanceof MercuryBitmap) {

MercuryBitmap other = (MercuryBitmap)that;

return this.num_bits == other.num_bits

&& java.util.Arrays.equals(this.elements, other.elements);

}

return false;

}

public boolean getBit(int bit)

{

return (elements[byteIndexForBit(bit)]

& (1 << bitIndexWithinByte(bit))) != 0;

}

public void setBit(int bit)

{

byte b;

b = elements[byteIndexForBit(bit)];

b |= 1 << bitIndexWithinByte(bit);

elements[byteIndexForBit(bit)] = b;

}

public void clearBit(int bit)

{

byte b;

b = elements[byteIndexForBit(bit)];

b &= ~(1 << bitIndexWithinByte(bit));

elements[byteIndexForBit(bit)] = b;

}

public static int byteIndexForBit(int bit) {

return bit / BITS_PER_BYTE;

}

public static int bitIndexWithinByte(int bit) {

return bit % BITS_PER_BYTE;

}

mercury/java/runtime/MercuryBitmap.java at master · Mercury-Language/mercury · GitHub

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