/**
* Copyright 2016 LinkedIn Corp. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
*/
package com.github.ambry.utils;
/** A variety of high efficiency bit twiddling routines.
* @lucene.internal
*/
final class BitUtil {
/** Returns the number of bits set in the long */
public static int pop(long x) {
/* Hacker's Delight 32 bit pop function:
* http://www.hackersdelight.org/HDcode/newCode/pop_arrayHS.cc
*
int pop(unsigned x) {
x = x - ((x >> 1) & 0x55555555);
x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
x = (x + (x >> 4)) & 0x0F0F0F0F;
x = x + (x >> 8);
x = x + (x >> 16);
return x & 0x0000003F;
}
***/
// 64 bit java version of the C function from above
x = x - ((x >>> 1) & 0x5555555555555555L);
x = (x & 0x3333333333333333L) + ((x >>> 2) & 0x3333333333333333L);
x = (x + (x >>> 4)) & 0x0F0F0F0F0F0F0F0FL;
x = x + (x >>> 8);
x = x + (x >>> 16);
x = x + (x >>> 32);
return ((int) x) & 0x7F;
}
/*** Returns the number of set bits in an array of longs. */
public static long pop_array(long A[], int wordOffset, int numWords) {
/*
* Robert Harley and David Seal's bit counting algorithm, as documented
* in the revisions of Hacker's Delight
* http://www.hackersdelight.org/revisions.pdf
* http://www.hackersdelight.org/HDcode/newCode/pop_arrayHS.cc
*
* This function was adapted to Java, and extended to use 64 bit words.
* if only we had access to wider registers like SSE from java...
*
* This function can be transformed to compute the popcount of other functions
* on bitsets via something like this:
* sed 's/A\[\([^]]*\)\]/\(A[\1] \& B[\1]\)/g'
*
*/
int n = wordOffset + numWords;
long tot = 0, tot8 = 0;
long ones = 0, twos = 0, fours = 0;
int i;
for (i = wordOffset; i <= n - 8; i += 8) {
/*** C macro from Hacker's Delight
#define CSA(h,l, a,b,c) \
{unsigned u = a ^ b; unsigned v = c; \
h = (a & b) | (u & v); l = u ^ v;}
***/
long twosA, twosB, foursA, foursB, eights;
// CSA(twosA, ones, ones, A[i], A[i+1])
{
long b = A[i], c = A[i + 1];
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
// CSA(twosB, ones, ones, A[i+2], A[i+3])
{
long b = A[i + 2], c = A[i + 3];
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
//CSA(foursA, twos, twos, twosA, twosB)
{
long u = twos ^ twosA;
foursA = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
//CSA(twosA, ones, ones, A[i+4], A[i+5])
{
long b = A[i + 4], c = A[i + 5];
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
// CSA(twosB, ones, ones, A[i+6], A[i+7])
{
long b = A[i + 6], c = A[i + 7];
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
//CSA(foursB, twos, twos, twosA, twosB)
{
long u = twos ^ twosA;
foursB = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
//CSA(eights, fours, fours, foursA, foursB)
{
long u = fours ^ foursA;
eights = (fours & foursA) | (u & foursB);
fours = u ^ foursB;
}
tot8 += pop(eights);
}
// handle trailing words in a binary-search manner...
// derived from the loop above by setting specific elements to 0.
// the original method in Hackers Delight used a simple for loop:
// for (i = i; i < n; i++) // Add in the last elements
// tot = tot + pop(A[i]);
if (i <= n - 4) {
long twosA, twosB, foursA, eights;
{
long b = A[i], c = A[i + 1];
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
{
long b = A[i + 2], c = A[i + 3];
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
{
long u = twos ^ twosA;
foursA = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
eights = fours & foursA;
fours = fours ^ foursA;
tot8 += pop(eights);
i += 4;
}
if (i <= n - 2) {
long b = A[i], c = A[i + 1];
long u = ones ^ b;
long twosA = (ones & b) | (u & c);
ones = u ^ c;
long foursA = twos & twosA;
twos = twos ^ twosA;
long eights = fours & foursA;
fours = fours ^ foursA;
tot8 += pop(eights);
i += 2;
}
if (i < n) {
tot += pop(A[i]);
}
tot += (pop(fours) << 2) + (pop(twos) << 1) + pop(ones) + (tot8 << 3);
return tot;
}
/** Returns the popcount or cardinality of the two sets after an intersection.
* Neither array is modified.
*/
public static long pop_intersect(long A[], long B[], int wordOffset, int numWords) {
// generated from pop_array via sed 's/A\[\([^]]*\)\]/\(A[\1] \& B[\1]\)/g'
int n = wordOffset + numWords;
long tot = 0, tot8 = 0;
long ones = 0, twos = 0, fours = 0;
int i;
for (i = wordOffset; i <= n - 8; i += 8) {
long twosA, twosB, foursA, foursB, eights;
// CSA(twosA, ones, ones, (A[i] & B[i]), (A[i+1] & B[i+1]))
{
long b = (A[i] & B[i]), c = (A[i + 1] & B[i + 1]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
// CSA(twosB, ones, ones, (A[i+2] & B[i+2]), (A[i+3] & B[i+3]))
{
long b = (A[i + 2] & B[i + 2]), c = (A[i + 3] & B[i + 3]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
//CSA(foursA, twos, twos, twosA, twosB)
{
long u = twos ^ twosA;
foursA = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
//CSA(twosA, ones, ones, (A[i+4] & B[i+4]), (A[i+5] & B[i+5]))
{
long b = (A[i + 4] & B[i + 4]), c = (A[i + 5] & B[i + 5]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
// CSA(twosB, ones, ones, (A[i+6] & B[i+6]), (A[i+7] & B[i+7]))
{
long b = (A[i + 6] & B[i + 6]), c = (A[i + 7] & B[i + 7]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
//CSA(foursB, twos, twos, twosA, twosB)
{
long u = twos ^ twosA;
foursB = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
//CSA(eights, fours, fours, foursA, foursB)
{
long u = fours ^ foursA;
eights = (fours & foursA) | (u & foursB);
fours = u ^ foursB;
}
tot8 += pop(eights);
}
if (i <= n - 4) {
long twosA, twosB, foursA, eights;
{
long b = (A[i] & B[i]), c = (A[i + 1] & B[i + 1]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
{
long b = (A[i + 2] & B[i + 2]), c = (A[i + 3] & B[i + 3]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
{
long u = twos ^ twosA;
foursA = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
eights = fours & foursA;
fours = fours ^ foursA;
tot8 += pop(eights);
i += 4;
}
if (i <= n - 2) {
long b = (A[i] & B[i]), c = (A[i + 1] & B[i + 1]);
long u = ones ^ b;
long twosA = (ones & b) | (u & c);
ones = u ^ c;
long foursA = twos & twosA;
twos = twos ^ twosA;
long eights = fours & foursA;
fours = fours ^ foursA;
tot8 += pop(eights);
i += 2;
}
if (i < n) {
tot += pop((A[i] & B[i]));
}
tot += (pop(fours) << 2) + (pop(twos) << 1) + pop(ones) + (tot8 << 3);
return tot;
}
/** Returns the popcount or cardinality of the union of two sets.
* Neither array is modified.
*/
public static long pop_union(long A[], long B[], int wordOffset, int numWords) {
// generated from pop_array via sed 's/A\[\([^]]*\)\]/\(A[\1] \| B[\1]\)/g'
int n = wordOffset + numWords;
long tot = 0, tot8 = 0;
long ones = 0, twos = 0, fours = 0;
int i;
for (i = wordOffset; i <= n - 8; i += 8) {
/*** C macro from Hacker's Delight
#define CSA(h,l, a,b,c) \
{unsigned u = a ^ b; unsigned v = c; \
h = (a & b) | (u & v); l = u ^ v;}
***/
long twosA, twosB, foursA, foursB, eights;
// CSA(twosA, ones, ones, (A[i] | B[i]), (A[i+1] | B[i+1]))
{
long b = (A[i] | B[i]), c = (A[i + 1] | B[i + 1]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
// CSA(twosB, ones, ones, (A[i+2] | B[i+2]), (A[i+3] | B[i+3]))
{
long b = (A[i + 2] | B[i + 2]), c = (A[i + 3] | B[i + 3]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
//CSA(foursA, twos, twos, twosA, twosB)
{
long u = twos ^ twosA;
foursA = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
//CSA(twosA, ones, ones, (A[i+4] | B[i+4]), (A[i+5] | B[i+5]))
{
long b = (A[i + 4] | B[i + 4]), c = (A[i + 5] | B[i + 5]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
// CSA(twosB, ones, ones, (A[i+6] | B[i+6]), (A[i+7] | B[i+7]))
{
long b = (A[i + 6] | B[i + 6]), c = (A[i + 7] | B[i + 7]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
//CSA(foursB, twos, twos, twosA, twosB)
{
long u = twos ^ twosA;
foursB = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
//CSA(eights, fours, fours, foursA, foursB)
{
long u = fours ^ foursA;
eights = (fours & foursA) | (u & foursB);
fours = u ^ foursB;
}
tot8 += pop(eights);
}
if (i <= n - 4) {
long twosA, twosB, foursA, eights;
{
long b = (A[i] | B[i]), c = (A[i + 1] | B[i + 1]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
{
long b = (A[i + 2] | B[i + 2]), c = (A[i + 3] | B[i + 3]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
{
long u = twos ^ twosA;
foursA = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
eights = fours & foursA;
fours = fours ^ foursA;
tot8 += pop(eights);
i += 4;
}
if (i <= n - 2) {
long b = (A[i] | B[i]), c = (A[i + 1] | B[i + 1]);
long u = ones ^ b;
long twosA = (ones & b) | (u & c);
ones = u ^ c;
long foursA = twos & twosA;
twos = twos ^ twosA;
long eights = fours & foursA;
fours = fours ^ foursA;
tot8 += pop(eights);
i += 2;
}
if (i < n) {
tot += pop((A[i] | B[i]));
}
tot += (pop(fours) << 2) + (pop(twos) << 1) + pop(ones) + (tot8 << 3);
return tot;
}
/** Returns the popcount or cardinality of A & ~B
* Neither array is modified.
*/
public static long pop_andnot(long A[], long B[], int wordOffset, int numWords) {
// generated from pop_array via sed 's/A\[\([^]]*\)\]/\(A[\1] \& ~B[\1]\)/g'
int n = wordOffset + numWords;
long tot = 0, tot8 = 0;
long ones = 0, twos = 0, fours = 0;
int i;
for (i = wordOffset; i <= n - 8; i += 8) {
/*** C macro from Hacker's Delight
#define CSA(h,l, a,b,c) \
{unsigned u = a ^ b; unsigned v = c; \
h = (a & b) | (u & v); l = u ^ v;}
***/
long twosA, twosB, foursA, foursB, eights;
// CSA(twosA, ones, ones, (A[i] & ~B[i]), (A[i+1] & ~B[i+1]))
{
long b = (A[i] & ~B[i]), c = (A[i + 1] & ~B[i + 1]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
// CSA(twosB, ones, ones, (A[i+2] & ~B[i+2]), (A[i+3] & ~B[i+3]))
{
long b = (A[i + 2] & ~B[i + 2]), c = (A[i + 3] & ~B[i + 3]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
//CSA(foursA, twos, twos, twosA, twosB)
{
long u = twos ^ twosA;
foursA = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
//CSA(twosA, ones, ones, (A[i+4] & ~B[i+4]), (A[i+5] & ~B[i+5]))
{
long b = (A[i + 4] & ~B[i + 4]), c = (A[i + 5] & ~B[i + 5]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
// CSA(twosB, ones, ones, (A[i+6] & ~B[i+6]), (A[i+7] & ~B[i+7]))
{
long b = (A[i + 6] & ~B[i + 6]), c = (A[i + 7] & ~B[i + 7]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
//CSA(foursB, twos, twos, twosA, twosB)
{
long u = twos ^ twosA;
foursB = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
//CSA(eights, fours, fours, foursA, foursB)
{
long u = fours ^ foursA;
eights = (fours & foursA) | (u & foursB);
fours = u ^ foursB;
}
tot8 += pop(eights);
}
if (i <= n - 4) {
long twosA, twosB, foursA, eights;
{
long b = (A[i] & ~B[i]), c = (A[i + 1] & ~B[i + 1]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
{
long b = (A[i + 2] & ~B[i + 2]), c = (A[i + 3] & ~B[i + 3]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
{
long u = twos ^ twosA;
foursA = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
eights = fours & foursA;
fours = fours ^ foursA;
tot8 += pop(eights);
i += 4;
}
if (i <= n - 2) {
long b = (A[i] & ~B[i]), c = (A[i + 1] & ~B[i + 1]);
long u = ones ^ b;
long twosA = (ones & b) | (u & c);
ones = u ^ c;
long foursA = twos & twosA;
twos = twos ^ twosA;
long eights = fours & foursA;
fours = fours ^ foursA;
tot8 += pop(eights);
i += 2;
}
if (i < n) {
tot += pop((A[i] & ~B[i]));
}
tot += (pop(fours) << 2) + (pop(twos) << 1) + pop(ones) + (tot8 << 3);
return tot;
}
public static long pop_xor(long A[], long B[], int wordOffset, int numWords) {
int n = wordOffset + numWords;
long tot = 0, tot8 = 0;
long ones = 0, twos = 0, fours = 0;
int i;
for (i = wordOffset; i <= n - 8; i += 8) {
/*** C macro from Hacker's Delight
#define CSA(h,l, a,b,c) \
{unsigned u = a ^ b; unsigned v = c; \
h = (a & b) | (u & v); l = u ^ v;}
***/
long twosA, twosB, foursA, foursB, eights;
// CSA(twosA, ones, ones, (A[i] ^ B[i]), (A[i+1] ^ B[i+1]))
{
long b = (A[i] ^ B[i]), c = (A[i + 1] ^ B[i + 1]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
// CSA(twosB, ones, ones, (A[i+2] ^ B[i+2]), (A[i+3] ^ B[i+3]))
{
long b = (A[i + 2] ^ B[i + 2]), c = (A[i + 3] ^ B[i + 3]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
//CSA(foursA, twos, twos, twosA, twosB)
{
long u = twos ^ twosA;
foursA = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
//CSA(twosA, ones, ones, (A[i+4] ^ B[i+4]), (A[i+5] ^ B[i+5]))
{
long b = (A[i + 4] ^ B[i + 4]), c = (A[i + 5] ^ B[i + 5]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
// CSA(twosB, ones, ones, (A[i+6] ^ B[i+6]), (A[i+7] ^ B[i+7]))
{
long b = (A[i + 6] ^ B[i + 6]), c = (A[i + 7] ^ B[i + 7]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
//CSA(foursB, twos, twos, twosA, twosB)
{
long u = twos ^ twosA;
foursB = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
//CSA(eights, fours, fours, foursA, foursB)
{
long u = fours ^ foursA;
eights = (fours & foursA) | (u & foursB);
fours = u ^ foursB;
}
tot8 += pop(eights);
}
if (i <= n - 4) {
long twosA, twosB, foursA, eights;
{
long b = (A[i] ^ B[i]), c = (A[i + 1] ^ B[i + 1]);
long u = ones ^ b;
twosA = (ones & b) | (u & c);
ones = u ^ c;
}
{
long b = (A[i + 2] ^ B[i + 2]), c = (A[i + 3] ^ B[i + 3]);
long u = ones ^ b;
twosB = (ones & b) | (u & c);
ones = u ^ c;
}
{
long u = twos ^ twosA;
foursA = (twos & twosA) | (u & twosB);
twos = u ^ twosB;
}
eights = fours & foursA;
fours = fours ^ foursA;
tot8 += pop(eights);
i += 4;
}
if (i <= n - 2) {
long b = (A[i] ^ B[i]), c = (A[i + 1] ^ B[i + 1]);
long u = ones ^ b;
long twosA = (ones & b) | (u & c);
ones = u ^ c;
long foursA = twos & twosA;
twos = twos ^ twosA;
long eights = fours & foursA;
fours = fours ^ foursA;
tot8 += pop(eights);
i += 2;
}
if (i < n) {
tot += pop((A[i] ^ B[i]));
}
tot += (pop(fours) << 2) + (pop(twos) << 1) + pop(ones) + (tot8 << 3);
return tot;
}
/* python code to generate ntzTable
def ntz(val):
if val==0: return 8
i=0
while (val&0x01)==0:
i = i+1
val >>= 1
return i
print ','.join([ str(ntz(i)) for i in range(256) ])
***/
/** keyspaceName of number of trailing zeros in a byte */
public static final byte[] ntzTable =
{8, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 6, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 7, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 6, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0};
/** Returns number of trailing zeros in a 64 bit long value. */
public static int ntz(long val) {
// A full binary search to determine the low byte was slower than
// a linear search for nextSetBit(). This is most likely because
// the implementation of nextSetBit() shifts bits to the right, increasing
// the probability that the first non-zero byte is in the rhs.
//
// This implementation does a single binary search at the top level only
// so that all other bit shifting can be done on ints instead of longs to
// remain friendly to 32 bit architectures. In addition, the case of a
// non-zero first byte is checked for first because it is the most common
// in dense bit arrays.
int lower = (int) val;
int lowByte = lower & 0xff;
if (lowByte != 0) {
return ntzTable[lowByte];
}
if (lower != 0) {
lowByte = (lower >>> 8) & 0xff;
if (lowByte != 0) {
return ntzTable[lowByte] + 8;
}
lowByte = (lower >>> 16) & 0xff;
if (lowByte != 0) {
return ntzTable[lowByte] + 16;
}
// no need to mask off low byte for the last byte in the 32 bit word
// no need to check for zero on the last byte either.
return ntzTable[lower >>> 24] + 24;
} else {
// grab upper 32 bits
int upper = (int) (val >> 32);
lowByte = upper & 0xff;
if (lowByte != 0) {
return ntzTable[lowByte] + 32;
}
lowByte = (upper >>> 8) & 0xff;
if (lowByte != 0) {
return ntzTable[lowByte] + 40;
}
lowByte = (upper >>> 16) & 0xff;
if (lowByte != 0) {
return ntzTable[lowByte] + 48;
}
// no need to mask off low byte for the last byte in the 32 bit word
// no need to check for zero on the last byte either.
return ntzTable[upper >>> 24] + 56;
}
}
/** Returns number of trailing zeros in a 32 bit int value. */
public static int ntz(int val) {
// This implementation does a single binary search at the top level only.
// In addition, the case of a non-zero first byte is checked for first
// because it is the most common in dense bit arrays.
int lowByte = val & 0xff;
if (lowByte != 0) {
return ntzTable[lowByte];
}
lowByte = (val >>> 8) & 0xff;
if (lowByte != 0) {
return ntzTable[lowByte] + 8;
}
lowByte = (val >>> 16) & 0xff;
if (lowByte != 0) {
return ntzTable[lowByte] + 16;
}
// no need to mask off low byte for the last byte.
// no need to check for zero on the last byte either.
return ntzTable[val >>> 24] + 24;
}
/** returns 0 based index of first set bit
* (only works for x!=0)
* <br/> This is an alternate implementation of ntz()
*/
public static int ntz2(long x) {
int n = 0;
int y = (int) x;
if (y == 0) {
n += 32;
y = (int) (x >>> 32);
} // the only 64 bit shift necessary
if ((y & 0x0000FFFF) == 0) {
n += 16;
y >>>= 16;
}
if ((y & 0x000000FF) == 0) {
n += 8;
y >>>= 8;
}
return (ntzTable[y & 0xff]) + n;
}
/** returns 0 based index of first set bit
* <br/> This is an alternate implementation of ntz()
*/
public static int ntz3(long x) {
// another implementation taken from Hackers Delight, extended to 64 bits
// and converted to Java.
// Many 32 bit ntz algorithms are at http://www.hackersdelight.org/HDcode/ntz.cc
int n = 1;
// do the first step as a long, all others as ints.
int y = (int) x;
if (y == 0) {
n += 32;
y = (int) (x >>> 32);
}
if ((y & 0x0000FFFF) == 0) {
n += 16;
y >>>= 16;
}
if ((y & 0x000000FF) == 0) {
n += 8;
y >>>= 8;
}
if ((y & 0x0000000F) == 0) {
n += 4;
y >>>= 4;
}
if ((y & 0x00000003) == 0) {
n += 2;
y >>>= 2;
}
return n - (y & 1);
}
/** returns true if v is a power of two or zero*/
public static boolean isPowerOfTwo(int v) {
return ((v & (v - 1)) == 0);
}
/** returns true if v is a power of two or zero*/
public static boolean isPowerOfTwo(long v) {
return ((v & (v - 1)) == 0);
}
/** returns the next highest power of two, or the current value if it's already a power of two or zero*/
public static int nextHighestPowerOfTwo(int v) {
v--;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
v++;
return v;
}
/** returns the next highest power of two, or the current value if it's already a power of two or zero*/
public static long nextHighestPowerOfTwo(long v) {
v--;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
v |= v >> 32;
v++;
return v;
}
}