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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;
/**
* Operations on individual bits
*/
public class Bits
{
£<function table
{
if [ $1 = 0 ]; then
echo -n "${2}, "
else
level=$(( $1 - 1 ))
table $level $(( $2 + 0 ))
table $level $(( $2 + 1 ))
table $level $(( $2 + 1 ))
table $level $(( $2 + 2 ))
fi
£>}
/**
* Lookup table for the number of set bits in a byte
*/
private static byte[] ONES_TABLE_256 = { £(table 4 0) };
/* ONES_TABLE_256[0] = 0;
* for (int i = 0; i < 256; i++)
* ONES_TABLE_256[i] = (i & 1) + ONES_TABLE_256[i / 2];
*/
£<for T_S in char_2 byte_1 short_2 int_4 long_8; do
T=${T_S%_*}
£>S=${T_S#*_}
/**
* Sets or clears individual bits in an integer
*
* @param value The value to modify
* @param mask Mask of bits to modify
* @param flag 1 if the bit should be set, 0 if the bit should be clears
* @return The value with the bits modified
*/
public static £{T} set_clear(£{T} value, £{T} mask, £{T} flag)
{
return (£{T})(value ^ ((-flag ^ value) & mask));
}
/**
* Sets or clears individual bits in an integer, superscalar version
*
* @param value The value to modify
* @param mask Mask of bits to modify
* @param flag 1 if the bit should be set, 0 if the bit should be clears
* @return The value with the bits modified
*/
public static £{T} set_clear_superscalar(£{T} value, £{T} mask, £{T} flag)
{
return (£{T})((value & ~mask) | (-flag & mask));
}
/**
* Merge bits from two values
*
* @param zero Integer whose bits should be kept where the mask has zeroes
* @param one Integer whose bits should be kept where the mask has onces
* @param mask The merge mask
* @return {@code (zero & ~mask) | (one & mask)}
*/
public static £{T} merge(£{T} zero, £{T} one, £{T} mask)
{
return (£{T})(zero ^ ((£{T})(zero ^ one) & mask));
}
/**
* Clears the least significant bit set
*
* @param value The integer
* @return The value with its least significant set bit cleared
*/
public static £{T} clearLeastSignificant(£{T} value)
{
return (£{T})(value & (value - 1));
}
/**
* Calculate the number of set bits in an integer, naïve version
*
* @param value The integer
* @return The number of set bits
*/
public static £{T} ones_naïve(£{T} value)
{
£{T} count = 0;
for (; value != 0; value >>>= 1)
count += (£{T})(value & 1);
return count;
}
/**
* Calculate the number of set bits in an integer, Wegner's version
*
* @param value The integer
* @return The number of set bits
*/
public static £{T} ones_wegner(£{T} value)
{
£{T} count = 0;
for (; value != 0; count++)
value &= value - 1; /* clear the least significant bit set */
return count;
}
/**
* Calculate the number of set bits in an integer, partial lookup table version
*
* @param value The integer
* @return The number of set bits
*/
public static £{T} ones_table(£{T} value)
{
£>function lookup { echo "ONES_TABLE_256[(int)((value >> $1) & 255)]" ; }
return (£{T})((£{T})(£(lookup 0) + £(lookup 8)) + (£{T})(£(lookup 16) + £(lookup 24)));
/* In C you can split the value by getting the address of the value and cast the pointer to char* */
}
£>done
}
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