com.jogamp.common.util.Bitfield Maven / Gradle / Ivy
/**
* Copyright 2015 JogAmp Community. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are
* permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this list of
* conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice, this list
* of conditions and the following disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY JogAmp Community ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JogAmp Community OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* The views and conclusions contained in the software and documentation are those of the
* authors and should not be interpreted as representing official policies, either expressed
* or implied, of JogAmp Community.
*/
package com.jogamp.common.util;
import jogamp.common.util.SyncedBitfield;
/**
* Simple bitfield interface for efficient bit storage access in O(1).
* @since 2.3.2
*/
public interface Bitfield {
/** Maximum 32 bit Unsigned Integer Value: {@code 0xffffffff} == {@value}. */
public static final int UNSIGNED_INT_MAX_VALUE = 0xffffffff;
/**
* Bit operation utilities (static).
*/
public static class Util {
/**
* Maximum 32bit integer value being of {@link #isPowerOf2(int)}.
*
* We rely on the JVM spec {@link Integer#SIZE} == 32.
*
*/
public static final int MAX_POWER_OF_2 = 1 << ( Integer.SIZE - 2 );
/**
* Returns the 32 bit mask of n-bits, i.e. n low order 1’s.
*
* Implementation handles n == 32.
*
* @throws IndexOutOfBoundsException if {@code b} is out of bounds, i.e. > 32
*/
public static int getBitMask(final int n) {
if( 32 > n ) {
return ( 1 << n ) - 1;
} else if ( 32 == n ) {
return UNSIGNED_INT_MAX_VALUE;
} else {
throw new IndexOutOfBoundsException("n <= 32 expected, is "+n);
}
}
/**
* Returns the number of set bits within given 32bit integer in O(1)
* using a HAKEM 169 Bit Count inspired implementation:
*
* http://www.inwap.com/pdp10/hbaker/hakmem/hakmem.html
* http://home.pipeline.com/~hbaker1/hakmem/hacks.html#item169
* http://tekpool.wordpress.com/category/bit-count/
* http://www.hackersdelight.org/
*
*
* We rely on the JVM spec {@link Integer#SIZE} == 32.
*
*/
public static final int bitCount(int n) {
// Note: Original used 'unsigned int',
// hence we use the unsigned right-shift '>>>'
/**
* Original does not work due to lack of 'unsigned' right-shift and modulo,
* we need 2-complementary solution, i.e. 'signed'.
int c = n;
c -= (n >>> 1) & 033333333333;
c -= (n >>> 2) & 011111111111;
return ( (c + ( c >>> 3 ) ) & 030707070707 ) & 0x3f; // % 63
*/
// Hackers Delight, Figure 5-2, pop1 of pop.c.txt
n = n - ((n >>> 1) & 0x55555555);
n = (n & 0x33333333) + ((n >>> 2) & 0x33333333);
n = (n + (n >>> 4)) & 0x0f0f0f0f;
n = n + (n >>> 8);
n = n + (n >>> 16);
return n & 0x3f;
}
/**
* Returns {@code true} if the given integer is a power of 2
*
* Source: bithacks: http://www.graphics.stanford.edu/~seander/bithacks.html#DetermineIfPowerOf2
*
*/
public static final boolean isPowerOf2(final int n) {
return 0
* Source: bithacks: http://www.graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
*
*
* We rely on the JVM spec {@link Integer#SIZE} == 32.
*
*/
public static final int nextPowerOf2(int n) {
n--;
n |= n >>> 1;
n |= n >>> 2;
n |= n >>> 4;
n |= n >>> 8;
n |= n >>> 16;
return (n < 0) ? 1 : n + 1; // avoid edge case where n is 0, it would return 0, which isn't a power of 2
}
/**
* If the given {@code n} is not {@link #isPowerOf2(int)} return {@link #nextPowerOf2(int)},
* otherwise return {@code n} unchanged.
*
* return isPowerOf2(n) ? n : nextPowerOf2(n);
*
*
* We rely on the JVM spec {@link Integer#SIZE} == 32.
*
*/
public static final int roundToPowerOf2(final int n) {
return isPowerOf2(n) ? n : nextPowerOf2(n);
}
}
/**
* Simple {@link Bitfield} factory for returning the efficient implementation.
*/
public static class Factory {
/**
* Creates am efficient {@link Bitfield} instance based on the requested {@code storageBitSize}.
*
* Implementation returns a plain 32 bit integer field implementation for
* {@code storageBitSize} ≤ 32 bits or an 32 bit integer array implementation otherwise.
*
*/
public static Bitfield create(final int storageBitSize) {
if( 32 >= storageBitSize ) {
return new jogamp.common.util.Int32Bitfield();
} else {
return new jogamp.common.util.Int32ArrayBitfield(storageBitSize);
}
}
/**
* Creates a synchronized {@link Bitfield} by wrapping the given {@link Bitfield} instance.
*/
public static Bitfield synchronize(final Bitfield impl) {
return new SyncedBitfield(impl);
}
}
/**
* Returns the storage size in bit units, e.g. 32 bit for implementations using one {@code int} field.
*/
int size();
/**
* Set all bits of this bitfield to the given value {@code bit}.
*/
void clearField(final boolean bit);
/**
* Returns {@code length} bits from this storage,
* starting with the lowest bit from the storage position {@code lowBitnum}.
* @param lowBitnum storage bit position of the lowest bit, restricted to [0..{@link #size()}-{@code length}].
* @param length number of bits to read, constrained to [0..32].
* @throws IndexOutOfBoundsException if {@code rightBitnum} is out of bounds
* @see #put32(int, int, int)
*/
int get32(final int lowBitnum, final int length) throws IndexOutOfBoundsException;
/**
* Puts {@code length} bits of given {@code data} into this storage,
* starting w/ the lowest bit to the storage position {@code lowBitnum}.
* @param lowBitnum storage bit position of the lowest bit, restricted to [0..{@link #size()}-{@code length}].
* @param length number of bits to write, constrained to [0..32].
* @param data the actual bits to be put into this storage
* @throws IndexOutOfBoundsException if {@code rightBitnum} is out of bounds
* @see #get32(int, int)
*/
void put32(final int lowBitnum, final int length, final int data) throws IndexOutOfBoundsException;
/**
* Copies {@code length} bits at position {@code srcLowBitnum} to position {@code dstLowBitnum}
* and returning the bits.
*
* Implementation shall operate as if invoking {@link #get32(int, int)}
* and then {@link #put32(int, int, int)} sequentially.
*
* @param srcLowBitnum source bit number, restricted to [0..{@link #size()}-1].
* @param dstLowBitnum destination bit number, restricted to [0..{@link #size()}-1].
* @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
* @see #get32(int, int)
* @see #put32(int, int, int)
*/
int copy32(final int srcLowBitnum, final int dstLowBitnum, final int length) throws IndexOutOfBoundsException;
/**
* Return true if the bit at position bitnum is set, otherwise false.
* @param bitnum bit number, restricted to [0..{@link #size()}-1].
* @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
*/
boolean get(final int bitnum) throws IndexOutOfBoundsException;
/**
* Set or clear the bit at position bitnum according to bit
* and return the previous value.
* @param bitnum bit number, restricted to [0..{@link #size()}-1].
* @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
*/
boolean put(final int bitnum, final boolean bit) throws IndexOutOfBoundsException;
/**
* Set the bit at position bitnum according to bit.
* @param bitnum bit number, restricted to [0..{@link #size()}-1].
* @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
*/
void set(final int bitnum) throws IndexOutOfBoundsException;
/**
* Clear the bit at position bitnum according to bit.
* @param bitnum bit number, restricted to [0..{@link #size()}-1].
* @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
*/
void clear(final int bitnum) throws IndexOutOfBoundsException;
/**
* Copies the bit at position {@code srcBitnum} to position {@code dstBitnum}
* and returning true if the bit is set, otherwise false.
* @param srcBitnum source bit number, restricted to [0..{@link #size()}-1].
* @param dstBitnum destination bit number, restricted to [0..{@link #size()}-1].
* @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
*/
boolean copy(final int srcBitnum, final int dstBitnum) throws IndexOutOfBoundsException;
/**
* Returns the number of one bits within this bitfield.
*
* Utilizes {#link {@link Bitfield.Util#bitCount(int)}}.
*
*/
int bitCount();
}