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/**
* Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package algorithms.bits;
/**
* Power of 2 interger operations
*/
public class Powers
{
£<for T_S in char_2 byte_1 short_2 int_4 long_8; do
T=${T_S%_*}
£>S=${T_S#*_}
/**
* Compute whether an integer is a power of two,
* note that zero is indeed not a power of two
*
* @param value The integer
* @return Whether the integer is a power of two
*/
public static boolean isPowerOf2(£{T} value)
{
return (value & (value - 1)) == 0; /* The left hand side clears the least significant bit set */
/* Or alternatively: (value & -value) == value */
}
/**
* Computes the nearest, but higher, power of two,
* independently of whether the current value is
* a power of two or not
*
* @param value The current value
* @return The next power of two
*/
public static £{T} nextPowerOf2(£{T} value)
{
value |= value >> 1;
value |= value >> 2;
value |= value >> 4;
£>(( S > 1)) &&
value |= value >> 8;
£>(( S > 2)) &&
value |= value >> 16;
£>(( S > 4)) &&
value |= value >> 32;
return (£{T})(value + 1);
}
/**
* Computes the nearest, but higher, power of two,
* but only if the current value is not a power of two
*
* @param value The current value
* @return The next power of two
*/
public static £{T} toPowerOf2(£{T} value)
{
value -= 1;
value |= value >>> 1;
value |= value >>> 2;
value |= value >>> 4;
£>(( S > 1)) &&
value |= value >>> 8;
£>(( S > 2)) &&
value |= value >>> 16;
£>(( S > 4)) &&
value |= value >>> 32;
return (£{T})(value + 1);
}
£>done
}
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