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Bits.java
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Bits.java
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/*
* Copyright (c) 2002-2016 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.kernel.impl.util;
import java.util.Arrays;
/**
* Got bits to store, shift and retrieve and they are more than what fits in a long?
* Use {@link Bits} then.
*/
public final class Bits implements Cloneable
{
// 3: ...
// 2: [ 23 ][ 22 ][ 21 ][ 20 ][ 19 ][ 18 ][ 17 ][ 16 ] <--\
// |
// /---------------------------------------------------------------------------------------------/
// |
// 1: \-[ 15 ][ 14 ][ 13 ][ 12 ][ 11 ][ 10 ][ 9 ][ 8 ] <--\
// |
// /---------------------------------------------------------------------------------------------/
// |
// 0: \-[ 7 ][ 6 ][ 5 ][ 4 ][ 3 ][ 2 ][ 1 ][ 0 ] <---- START
private final long[] longs;
private final int numberOfBytes;
private int writePosition;
private int readPosition;
/*
* Calculate all the right overflow masks
*/
private static final long[] RIGHT_OVERFLOW_MASKS;
static
{
RIGHT_OVERFLOW_MASKS = new long[Long.SIZE];
long mask = 1L;
for ( int i = 0; i < RIGHT_OVERFLOW_MASKS.length; i++ )
{
RIGHT_OVERFLOW_MASKS[i] = mask;
mask <<= 1;
mask |= 0x1L;
}
}
public static Bits bits( int numberOfBytes )
{
int requiredLongs = requiredLongs( numberOfBytes );
return new Bits( new long[requiredLongs], numberOfBytes );
}
public static int requiredLongs( int numberOfBytes )
{
return ((numberOfBytes - 1) >> 3) + 1; // /8
}
public static Bits bitsFromLongs( long[] longs )
{
return new Bits( longs, longs.length << 3 ); // *8
}
public static Bits bitsFromBytes( byte[] bytes )
{
return bitsFromBytes( bytes, 0 );
}
public static Bits bitsFromBytes( byte[] bytes, int startIndex )
{
final int count = bytes.length;
Bits bits = bits( count - startIndex );
for ( int i = startIndex; i < count; i++ )
{
bits.put( bytes[i] );
}
return bits;
}
public static Bits bitsFromBytes( byte[] bytes, int offset, int length )
{
Bits bits = bits( length - offset );
for ( int i = offset; i < (offset + length); i++ )
{
bits.put( bytes[i] );
}
return bits;
}
private Bits( long[] longs, int numberOfBytes )
{
this.longs = longs;
this.numberOfBytes = numberOfBytes;
}
/**
* A mask which has the {@code steps} least significant bits set to 1, all others 0.
* It's used to carry bits over between carriers (longs) when shifting right.
*
* @param steps the number of least significant bits to have set to 1 in the mask.
* @return the created mask.
*/
public static long rightOverflowMask( int steps )
{
return RIGHT_OVERFLOW_MASKS[steps - 1];
}
/**
* Returns the underlying long values that has got all the bits applied.
* The first item in the array has got the most significant bits.
*
* @return the underlying long values that has got all the bits applied.
*/
@SuppressWarnings("EI_EXPOSE_REP")
public long[] getLongs()
{
return longs;
}
public byte[] asBytes()
{
int readPositionBefore = readPosition;
readPosition = 0;
try
{
byte[] result = new byte[numberOfBytes];
final int count = result.length;
for ( int i = 0; i < count; i++ )
{
result[i] = getByte();
}
return result;
}
finally
{
readPosition = readPositionBefore;
}
}
/**
* A very nice toString, showing each bit, divided into groups of bytes and
* lines of 8 bytes.
*/
@Override
public String toString()
{
StringBuilder builder = new StringBuilder();
for ( int longIndex = longs.length - 1; longIndex >= 0; longIndex-- )
{
long value = longs[longIndex];
if ( builder.length() > 0 )
{
builder.append( "\n" );
}
builder.append( longIndex );
builder.append( ':' );
numberToString( builder, value, 8 );
if ( longIndex == 0 )
{
builder.append( " <-- START" );
}
}
return builder.toString();
}
public static String numberToString( long value, int numberOfBytes )
{
return numberToString( new StringBuilder(), value, numberOfBytes ).toString();
}
public static StringBuilder numberToString( StringBuilder builder, long value, int numberOfBytes )
{
builder.append( "[" );
for ( int i = 8 * numberOfBytes - 1; i >= 0; i-- )
{
if ( i > 0 && i % 8 == 0 )
{
builder.append( "," );
}
boolean isSet = (value & (1L << i)) != 0;
builder.append( isSet ? "1" : "0" );
}
builder.append( "]" );
return builder;
}
public static String numbersToBitString( byte[] values )
{
StringBuilder builder = new StringBuilder();
for ( byte value : values )
{
numberToString( builder, value, 1 );
}
return builder.toString();
}
public static String numbersToBitString( short[] values )
{
StringBuilder builder = new StringBuilder();
for ( short value : values )
{
numberToString( builder, value, 2 );
}
return builder.toString();
}
public static String numbersToBitString( int[] values )
{
StringBuilder builder = new StringBuilder();
for ( int value : values )
{
numberToString( builder, value, 4 );
}
return builder.toString();
}
public static String numbersToBitString( long[] values )
{
StringBuilder builder = new StringBuilder();
for ( long value : values )
{
numberToString( builder, value, 8 );
}
return builder.toString();
}
@Override
public Bits clone()
{
return new Bits( Arrays.copyOf( longs, longs.length ), numberOfBytes );
}
public Bits put( byte value )
{
return put( value, Byte.SIZE );
}
public Bits put( byte value, int steps )
{
return put( (long) value, steps );
}
public Bits put( short value )
{
return put( value, Short.SIZE );
}
public Bits put( short value, int steps )
{
return put( (long) value, steps );
}
public Bits put( int value )
{
return put( value, Integer.SIZE );
}
public Bits put( int value, int steps )
{
return put( (long) value, steps );
}
public Bits put( long value )
{
return put( value, Long.SIZE );
}
public Bits put( long value, int steps )
{
int lowLongIndex = writePosition >> 6; // /64
int lowBitInLong = writePosition % 64;
int lowBitsAvailable = 64 - lowBitInLong;
long lowValueMask = rightOverflowMask( Math.min( lowBitsAvailable, steps ) );
longs[lowLongIndex] |= (((value) & lowValueMask) << lowBitInLong);
if ( steps > lowBitsAvailable )
{ // High bits
long highValueMask = rightOverflowMask( steps - lowBitsAvailable );
longs[lowLongIndex + 1] |= ((value) >>> lowBitsAvailable) & highValueMask;
}
writePosition += steps;
return this;
}
public Bits put( byte[] bytes, int offset, int length )
{
for ( int i = offset; i < offset + length; i++ )
{
put( bytes[i], Byte.SIZE );
}
return this;
}
public boolean available()
{
return readPosition < writePosition;
}
public byte getByte()
{
return getByte( Byte.SIZE );
}
public byte getByte( int steps )
{
return (byte) getLong( steps );
}
public short getShort()
{
return getShort( Short.SIZE );
}
public short getShort( int steps )
{
return (short) getLong( steps );
}
public int getInt()
{
return getInt( Integer.SIZE );
}
public int getInt( int steps )
{
return (int) getLong( steps );
}
public long getUnsignedInt()
{
return getInt( Integer.SIZE ) & 0xFFFFFFFFL;
}
public long getLong()
{
return getLong( Long.SIZE );
}
public long getLong( int steps )
{
int lowLongIndex = readPosition >> 6; // 64
int lowBitInLong = readPosition % 64;
int lowBitsAvailable = 64 - lowBitInLong;
long lowLongMask = rightOverflowMask( Math.min( lowBitsAvailable, steps ) ) << lowBitInLong;
long lowValue = longs[lowLongIndex] & lowLongMask;
long result = lowValue >>> lowBitInLong;
if ( steps > lowBitsAvailable )
{ // High bits
long highLongMask = rightOverflowMask( steps - lowBitsAvailable );
result |= ((longs[lowLongIndex + 1] & highLongMask) << lowBitsAvailable);
}
readPosition += steps;
return result;
}
public static boolean bitFlag( byte flags, byte flag )
{
assert (flag & (-flag)) == flag : "flag should be a power of 2, not: 0x" + Integer.toHexString( flag );
return (flags & flag) == flag;
}
public static byte bitFlag( boolean value, byte flag )
{
assert (flag & (-flag)) == flag : "flag should be a power of 2, not: 0x" + Integer.toHexString( flag );
return value ? flag : 0;
}
public static byte notFlag( byte flags, byte flag )
{
assert (flag & (-flag)) == flag : "flag should be a power of 2, not: 0x" + Integer.toHexString( flag );
return (byte) (flags & (~flag));
}
public static byte bitFlags( byte... flags )
{
byte result = 0;
for ( byte flag : flags )
{
result |= flag;
}
return result;
}
/**
* Clear the position and data.
*/
public void clear( boolean zeroBits )
{
if ( zeroBits )
{
// TODO optimize so that only the touched longs gets cleared
Arrays.fill( longs, 0L );
}
readPosition = writePosition = 0;
}
/**
* Given the write position, how many longs are in use.
*/
public int longsInUse()
{
return ((writePosition - 1) / Long.SIZE) + 1;
}
}