/**
* This file is part of ObjectFabric (http://objectfabric.org).
*
* ObjectFabric is licensed under the Apache License, Version 2.0, the terms
* of which may be found at http://www.apache.org/licenses/LICENSE-2.0.html.
*
* Copyright ObjectFabric Inc.
*
* This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
* WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
package org.objectfabric;
/**
* Manipulates bits in arrays of integers. Bits are stored in integers because 32 bits
* JVMs do not guarantee longs are read or written atomically.
*/
abstract class Bits {
public static final int BITS_PER_UNIT_SHIFT = 5; // 2 ^ 5 == 32
public static final int BITS_PER_UNIT = 1 << BITS_PER_UNIT_SHIFT;
public static final int BIT_INDEX_MASK = BITS_PER_UNIT - 1;
public static final int SPARSE_BITSET_DEFAULT_CAPACITY = 2;
/**
* For sparse arrays. Cannot use two arrays as elements must be written atomically
* during object version merges.
*/
public static final class Entry {
public int IntIndex;
public int Value;
public Entry(int intIndex, int value) {
IntIndex = intIndex;
Value = value;
}
}
private Bits() {
}
public static int arrayLength(int size) {
if (Debug.ENABLED)
Debug.assertion(size > 0);
return intIndex(size - 1) + 1;
}
public static boolean get(int value, int index) {
if (Debug.ENABLED)
Debug.assertion(index >= 0 && index < Integer.SIZE);
return (value & mask32(index)) != 0;
}
public static boolean get(Entry[] sparse, int index) {
if (Debug.ENABLED)
Debug.assertion(index >= 0);
if (Debug.ENABLED)
checkInvariants(sparse);
if (sparse != null) {
Entry entry = getEntry(sparse, intIndex(index));
if (entry != null)
return (entry.Value & maskArray(index)) != 0;
}
return false;
}
private static Entry getEntry(Entry[] sparse, int intIndex) {
int foldedIntIndex = intIndex & (sparse.length - 1);
for (int i = OpenMap.attemptsStart(sparse.length); i >= 0; i--) {
Entry current = sparse[foldedIntIndex];
if (current != null && current.IntIndex == intIndex)
return current;
foldedIntIndex = (foldedIntIndex + 1) & (sparse.length - 1);
}
return null;
}
public static int getFoldedIntIndexFromIndex(Entry[] sparse, int index) {
int intIndex = intIndex(index);
return getFoldedIntIndexFromIntIndex(sparse, intIndex);
}
public static int getFoldedIntIndexFromIntIndex(Entry[] sparse, int intIndex) {
if (Debug.ENABLED)
checkInvariants(sparse);
int foldedIntIndex = intIndex & (sparse.length - 1);
for (int i = OpenMap.attemptsStart(sparse.length); i >= 0; i--) {
Entry current = sparse[foldedIntIndex];
if (current != null && current.IntIndex == intIndex)
return foldedIntIndex;
foldedIntIndex = (foldedIntIndex + 1) & (sparse.length - 1);
}
return -1;
}
//
public static int set(int set, int index) {
if (Debug.ENABLED)
Debug.assertion(index >= 0 && index < Integer.SIZE);
return set | mask32(index);
}
public static int set(int set, int index, boolean value) {
if (Debug.ENABLED)
Debug.assertion(index >= 0 && index < Integer.SIZE);
int mask = mask32(index);
return value ? set | mask : set & ~mask;
}
public static Entry[] set(Entry[] sparse, int index) {
if (sparse == null)
sparse = new Bits.Entry[Bits.SPARSE_BITSET_DEFAULT_CAPACITY];
while (!tryToSet(sparse, index))
sparse = reindex(sparse);
return sparse;
}
public static boolean tryToSet(Entry[] sparse, int index) {
if (Debug.ENABLED)
Debug.assertion(index >= 0);
if (Debug.ENABLED)
checkInvariants(sparse);
int intIndex = intIndex(index);
int foldedIntIndex = intIndex & (sparse.length - 1);
for (int i = OpenMap.attemptsStart(sparse.length); i >= 0; i--) {
Entry current = sparse[foldedIntIndex];
if (current != null && current.IntIndex == intIndex) {
current.Value |= maskArray(index);
return true;
}
if (current == null) {
sparse[foldedIntIndex] = new Bits.Entry(intIndex, maskArray(index));
return true;
}
foldedIntIndex = (foldedIntIndex + 1) & (sparse.length - 1);
}
return false;
}
private static Entry[] reindex(Entry[] sparse) {
Entry[] old = sparse;
for (;;) {
sparse = new Bits.Entry[sparse.length << OpenMap.TIMES_TWO_SHIFT];
if (reindex(old, sparse))
break;
}
return sparse;
}
public static boolean reindex(Entry[] oldSparse, Entry[] newSparse) {
if (Debug.ENABLED) {
checkInvariants(oldSparse);
checkInvariants(newSparse);
}
for (int i = oldSparse.length - 1; i >= 0; i--)
if (oldSparse[i] != null)
if (add(newSparse, oldSparse[i]) < 0)
return false;
return true;
}
//
public static int add(Entry[] sparse, Entry entry) {
int foldedIntIndex = entry.IntIndex & (sparse.length - 1);
for (int i = OpenMap.attemptsStart(sparse.length); i >= 0; i--) {
Entry current = sparse[foldedIntIndex];
if (Debug.ENABLED)
if (current != null)
Debug.assertion(current.IntIndex != entry.IntIndex);
if (current == null) {
sparse[foldedIntIndex] = entry;
return foldedIntIndex;
}
foldedIntIndex = (foldedIntIndex + 1) & (sparse.length - 1);
}
return -1;
}
//
public static int unset(int set, int index) {
if (Debug.ENABLED)
Debug.assertion(index >= 0 && index < Integer.SIZE);
return set & ~mask32(index);
}
public static void unset(Entry[] sparse, int index) {
if (Debug.ENABLED)
Debug.assertion(index >= 0);
if (Debug.ENABLED)
checkInvariants(sparse);
int intIndex = intIndex(index);
int foldedIntIndex = intIndex & (sparse.length - 1);
for (int i = OpenMap.attemptsStart(sparse.length); i >= 0; i--) {
Entry current = sparse[foldedIntIndex];
if (current != null && current.IntIndex == intIndex) {
current.Value &= ~maskArray(index);
break;
}
if (current == null)
break;
foldedIntIndex = (foldedIntIndex + 1) & (sparse.length - 1);
}
}
//
public static boolean intersects(int a, int b) {
return (a & b) != 0;
}
public static boolean intersects(Entry[] a, Entry[] b) {
for (int i = a.length - 1; i >= 0; i--) {
if (a[i] != null) {
Entry current = getEntry(b, a[i].IntIndex);
if (current != null)
if ((a[i].Value & current.Value) != 0)
return true;
}
}
return false;
}
//
public static int merge(int value, int source) {
return value | source;
}
public static boolean mergeInPlace(Entry[] sparse, Entry[] source) {
if (Debug.ENABLED) {
checkInvariants(sparse);
checkInvariants(source);
}
for (int i = source.length - 1; i >= 0; i--)
if (source[i] != null && source[i].Value != 0)
if (!mergeInPlace(sparse, source[i]))
return false;
return true;
}
private static boolean mergeInPlace(Entry[] sparse, Entry entry) {
int foldedIntIndex = entry.IntIndex & (sparse.length - 1);
for (int i = OpenMap.attemptsStart(sparse.length); i >= 0; i--) {
Entry current = sparse[foldedIntIndex];
if (current != null && current.IntIndex == entry.IntIndex) {
current.Value |= entry.Value;
return true;
}
if (current == null) {
sparse[foldedIntIndex] = entry;
return true;
}
foldedIntIndex = (foldedIntIndex + 1) & (sparse.length - 1);
}
return false;
}
public static boolean mergeByCopy(Entry[] sparse, Entry[] source) {
if (Debug.ENABLED) {
checkInvariants(sparse);
checkInvariants(source);
}
for (int i = source.length - 1; i >= 0; i--)
if (source[i] != null && source[i].Value != 0)
if (!mergeByCopy(sparse, source[i]))
return false;
return true;
}
private static boolean mergeByCopy(Entry[] sparse, Entry entry) {
int foldedIntIndex = entry.IntIndex & (sparse.length - 1);
for (int i = OpenMap.attemptsStart(sparse.length); i >= 0; i--) {
Entry current = sparse[foldedIntIndex];
if (current != null && current.IntIndex == entry.IntIndex) {
sparse[foldedIntIndex] = new Bits.Entry(current.IntIndex, current.Value | entry.Value);
return true;
}
if (current == null) {
sparse[foldedIntIndex] = entry;
return true;
}
foldedIntIndex = (foldedIntIndex + 1) & (sparse.length - 1);
}
return false;
}
//
public static Entry[] clone(Entry[] sparse) {
if (Debug.ENABLED)
checkInvariants(sparse);
Entry[] clone = new Bits.Entry[sparse.length];
for (int i = sparse.length - 1; i >= 0; i--)
if (sparse[i] != null)
clone[i] = new Bits.Entry(sparse[i].IntIndex, sparse[i].Value);
return clone;
}
//
public static int and(int a, int b) {
return a & b;
}
public static Entry[] and(Entry[] a, Entry[] b) {
if (Debug.ENABLED) {
checkInvariants(a);
checkInvariants(b);
}
if (Debug.ENABLED) { // Should not call for nothing
boolean empty = true;
for (int i = b.length - 1; i >= 0; i--) {
if (b[i] != null) {
Debug.assertion(b[i].Value != 0);
empty = false;
}
}
Debug.assertion(!empty);
}
Entry[] result = new Bits.Entry[a.length];
for (int i = a.length - 1; i >= 0; i--)
if (a[i] != null)
result[i] = and(a[i], b);
return result;
}
private static Entry and(Entry entry, Entry[] mask) {
int foldedIntIndex = entry.IntIndex & (mask.length - 1);
for (int i = OpenMap.attemptsStart(mask.length); i >= 0; i--) {
Entry current = mask[foldedIntIndex];
if (current != null && current.IntIndex == entry.IntIndex)
return new Bits.Entry(entry.IntIndex, entry.Value & current.Value);
if (current == null)
return entry;
foldedIntIndex = (foldedIntIndex + 1) & (mask.length - 1);
}
return entry;
}
//
public static int andNot(int a, int b) {
return a & ~b;
}
public static Entry[] andNot(Entry[] a, Entry[] b) {
if (Debug.ENABLED) {
checkInvariants(a);
checkInvariants(b);
}
Entry[] result = null;
if (a != null) {
for (int i = a.length - 1; i >= 0; i--) {
if (a[i] != null) {
Entry entry = andNot(a[i], b);
if (entry != null) {
if (result == null)
result = new Bits.Entry[a.length];
result[i] = entry;
}
}
}
}
return result;
}
private static Entry andNot(Entry entry, Entry[] mask) {
if (mask != null) {
int foldedIntIndex = entry.IntIndex & (mask.length - 1);
for (int i = OpenMap.attemptsStart(mask.length); i >= 0; i--) {
Entry current = mask[foldedIntIndex];
if (current != null && current.IntIndex == entry.IntIndex) {
int value = entry.Value & ~current.Value;
if (value == 0)
return null;
return new Bits.Entry(entry.IntIndex, value);
}
if (current == null)
return entry;
foldedIntIndex = (foldedIntIndex + 1) & (mask.length - 1);
}
}
return entry;
}
//
public static boolean isEmpty(int value) {
return value == 0;
}
public static boolean isEmpty(Entry[] sparse) {
/*
* TODO make sure everywhere if array is created, it is not empty, switch test to
* != null.
*/
if (sparse != null)
for (int i = sparse.length - 1; i >= 0; i--)
if (sparse[i] != null && sparse[i].Value != 0)
return false;
return true;
}
//
public static int remove(int set, int index) {
int mod = index & BIT_INDEX_MASK;
if (mod == 0) // Cannot shift by 32
return set >>> 1;
return (set & (-1 >>> (32 - mod))) | ((set >>> 1) & (-1 << mod));
}
//
/**
* Given a bit index return unit index containing it.
*/
private static int intIndex(int index) {
return index >> BITS_PER_UNIT_SHIFT;
}
/**
* Given a bit index, return a integer that masks that bit in its integer.
*/
private static int mask32(int index) {
if (Debug.ENABLED)
Debug.assertion(index == (index & BIT_INDEX_MASK));
return 1 << index;
}
private static int maskArray(int index) {
return 1 << (index & BIT_INDEX_MASK);
}
// Debug
private static void checkInvariants(Entry[] sparse) {
if (!Debug.ENABLED)
Debug.assertAlways(false);
if (sparse != null) {
Debug.assertion(Utils.nextPowerOf2(sparse.length) == sparse.length);
for (int j = sparse.length - 1; j >= 0; j--) {
if (sparse[j] != null) {
if (j != (sparse[j].IntIndex & (sparse.length - 1)))
Debug.assertion(sparse[(j - 1) & (sparse.length - 1)] != null);
if (Debug.SLOW_CHECKS)
for (int i = sparse.length - 1; i > j; i--)
Debug.assertion(sparse[j] == null || sparse[i] == null || sparse[j].IntIndex != sparse[i].IntIndex);
}
}
}
}
}