* 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/
*
*/
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;
}
}
/**
* 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; /** * Returntrue 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
*/
void 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(); }