org.apache.hudi.org.openjdk.jol.util.SimpleIdentityHashSet Maven / Gradle / Ivy
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* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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package org.openjdk.jol.util;
/**
* Identity hash set implementation optimized for JOL uses. Cuts corners where it can.
*/
public final class SimpleIdentityHashSet {
private static final int MINIMUM_CAPACITY = 4;
private static final int MAXIMUM_CAPACITY = 1 << 29;
private Object[] table;
private int size;
public SimpleIdentityHashSet() {
table = new Object[capacity(MINIMUM_CAPACITY)];
}
private static int capacity(int expectedMaxSize) {
return (expectedMaxSize > MAXIMUM_CAPACITY / 3) ? MAXIMUM_CAPACITY :
(expectedMaxSize <= 2 * MINIMUM_CAPACITY / 3) ? MINIMUM_CAPACITY :
Integer.highestOneBit(expectedMaxSize + (expectedMaxSize << 1));
}
private static int hash(Object x, int length) {
return System.identityHashCode(x) & (length - 1);
}
private static int nextIndex(int i, int len) {
return (i + 1 < len ? i + 1 : 0);
}
public boolean add(Object o) {
while (true) {
final Object[] tab = table;
final int len = tab.length;
int i = hash(o, len);
for (Object item; (item = tab[i]) != null; i = nextIndex(i, len)) {
if (item == o) {
return false;
}
}
final int s = size + 1;
if (s*3 > len && resize(len)) continue;
tab[i] = o;
size = s;
return true;
}
}
private boolean resize(int newCapacity) {
int newLength = newCapacity * 2;
Object[] oldTable = table;
int oldLength = oldTable.length;
if (oldLength == 2 * MAXIMUM_CAPACITY) { // can't expand any further
if (size == MAXIMUM_CAPACITY - 1) {
throw new IllegalStateException("Capacity exhausted.");
}
return false;
}
if (oldLength >= newLength)
return false;
Object[] newTable = new Object[newLength];
for (Object o : oldTable) {
if (o != null) {
int i = hash(o, newLength);
while (newTable[i] != null) {
i = nextIndex(i, newLength);
}
newTable[i] = o;
}
}
table = newTable;
return true;
}
}